Patent Application
20200122133
The present invention relates to catalytic processes employing particular rhodium catalysts, as well as to the rhodium catalysts themselves. More specifically, the present invention relates to the alkene isomerisation, transfer dehydrogenation and dimerization catalytic processes employing the rhodium catalysts.
The transition-metal promoted isomerisation of alkenes is an atom efficient process that has many applications in industry and finechemicals synthesis;1-3 such as the Shell Higher Olefin Process,4 olefin conversion technologies that produce propene from butene/ethene mixtures,5-8 and the isomerisation of functionalised alkenes.9 Homogenous processes are well-studied for a wide range of transition metal catalysts1, 9-11 and commonly, although by no means exclusively, use catalysts based upon later transition metals such as Co,12 Ni,13, 14 Ru,15, 16Rh,17-19Ir,20-22 which operate at relatively low temperatures (e.g. 120° C. or lower), sometimes at room temperature.18, 19, 23-25 Heterogeneous, or supported, systems are also wellestablished, but these often require higher temperatures to operate.26,27 Alkene isomerisation also plays a key role in alkane dehydrogenation,28 and subsequent tandem upgrading processes such as metathesis29 or dimerisation,30,31 where the kinetic product of dehydrogenation is a terminal alkene that can then undergo isomerization (Scheme 1).32
The dehydrogenation of light alkanes such as butane and pentane, and their subsequent isomerization is particularly interesting, as while these alkanes are unsuitable as transportation fuels or feedstock chemicals, their corresponding alkenes have myriad uses.30, 31, 33 The discovery of abundant sources of light alkanes in shale and offshore gas fields provides additional motivation to study their conversion into fuels and commodity chemicals.34 As light alkanes are gaseous at, or close to, room temperature and pressure, the opportunity for solid/gas catalytic processes under these conditions is presented. Such conditions are also attractive due to physical separation of catalyst and substrates/product that they offer as well as opportunities to reduce catalyst decomposition through thermallyinduced processes.
Although heterogeneous solidgas systems for alkane dehydrogenation and alkene isomerization are well known,27, 35, 36 they often require high temperatures for their operation which leads to reductions in selectivity as well as catalyst deactivation through processes such a coking.
The present invention was devised with the foregoing in mind.
According to a first aspect of the present invention there is provided a catalytic process comprising the step of:
According to a further aspect of the present invention there is provided a catalytic process comprising the step of:
According to a further aspect of the present invention there is provided a compound having a structure according to formula (Ia) shown below:
wherein
According to a further aspect of the present invention there is provided a compound having a structure according to formula (Ia) shown below:
wherein
Unless otherwise stated, the following terms used in the specification and claims have the following meanings set out below.
The term “(m-nC)” or “(m-nC) group” used alone or as a prefix, refers to any group having m to n carbon atoms.
The term “alkyl” includes both straight and branched chain alkyl groups. References to individual alkyl groups such as “propyl” are specific for the straight chain version only and references to individual branched chain alkyl groups such as “isopropyl” are specific for the branched chain version only. For example, “(1-6C)alkyl” includes (1-4C)alkyl, (1-3C)alkyl, propyl, isopropyl and t-butyl. A similar convention applies to other radicals, for example “phenyl(1-6C)alkyl” includes phenyl(1-4C)alkyl, benzyl, 1-phenylethyl and 2-phenylethyl.
The term “halo” refers to fluoro, chloro, bromo and iodo.
The term “haloalkyl” or “haloalkoxy” is used herein to refer to an alkyl or alkoxy group respectively in which one or more hydrogen atoms have been replaced by halogen (e.g. fluorine) atoms. Examples of haloalkyl and haloalkoxy groups include fluoroalkyl and fluoroalkoxy groups such as —CHF2, —CH2CF3, or perfluoroalkyl/alkoxy groups such as —CF3, —CF2CF3, —OCF3, —OC(CF3)3 and —OCF2CF3.
The term “carbocyclyl”, “carbocyclic” or “carbocycle” means a non-aromatic, saturated or partially saturated monocyclic, or a fused, bridged, or spiro bicyclic ring system(s) based exclusively on carbon. Monocyclic carbocyclic rings contain from about 3 to 12 (suitably from 3 to 7) ring atoms. Bicyclic carbocycles contain from 7 to 17 carbon atoms in the rings, suitably 7 to 12 carbon atoms, in the rings. Bicyclic carbocyclic rings may be fused, spiro, or bridged ring systems.
The term “cycloalkyl” or “cycloalkane” means a saturated fused, bridged, or spiro bicyclic ring system(s) based exclusively on carbon. Monocyclic cycloalkanes contain from about 3 to 12 (suitably from 3 to 7) ring atoms. Bicyclic cycloalkanes contain from 7 to 17 carbon atoms in the rings, suitably 7 to 12 carbon atoms, in the rings. Bicyclic cycloalkanes may be fused, spiro, or bridged ring systems.
The term “cycloalkenyl” or “cycloalkene” means an unsaturated fused, bridged, or spiro bicyclic ring system(s) based exclusively on carbon. Monocyclic cycloalkenes contain from about 6 to 12 (suitably from 6 to 7) ring atoms. Bicyclic cycloalkenes contain from 7 to 17 carbon atoms in the rings, suitably 7 to 12 carbon atoms, in the rings. Bicyclic cycloalkenes may be fused, spiro, or bridged ring systems.
The term “heterocyclyl”, “heterocyclic” or “heterocycle” means a non-aromatic saturated or partially saturated monocyclic, fused, bridged, or spiro bicyclic heterocyclic ring system(s). Monocyclic heterocyclic rings contain from about 3 to 12 (suitably from 3 to 7) ring atoms, with from 1 to 5 (suitably 1, 2 or 3) heteroatoms selected from nitrogen, oxygen or sulfur in the ring. Bicyclic heterocycles contain from 7 to 17 member atoms, suitably 7 to 12 member atoms, in the ring. Bicyclic heterocyclic(s) rings may be fused, spiro, or bridged ring systems. Examples of heterocyclic groups include cyclic ethers such as oxiranyl, oxetanyl, tetrahydrofuranyl, dioxanyl, and substituted cyclic ethers. Heterocycles containing nitrogen include, for example, azetidinyl, pyrrolidinyl, piperidinyl, piperazinyl, tetrahydrotriazinyl, tetrahydropyrazolyl, and the like. Typical sulfur containing heterocycles include tetrahydrothienyl, dihydro-1,3-dithiol, tetrahydro-2H-thiopyran, and hexahydrothiepine. Other heterocycles include dihydro-oxathiolyl, tetrahydro-oxazolyl, tetrahydro-oxadiazolyl, tetrahydrodioxazolyl, tetrahydro-oxathiazolyl, hexahydrotriazinyl, tetrahydro-oxazinyl, morpholinyl, thiomorpholinyl, tetrahydropyrimidinyl, dioxolinyl, octahydrobenzofuranyl, octahydrobenzimidazolyl, and octahydrobenzothiazolyl. For heterocycles containing sulfur, the oxidized sulfur heterocycles containing SO or SO2 groups are also included. Examples include the sulfoxide and sulfone forms of tetrahydrothienyl and thiomorpholinyl such as tetrahydrothiene 1,1-dioxide and thiomorpholinyl 1,1-dioxide. A suitable value for a heterocyclyl group which bears 1 or 2 oxo (═O) or thioxo (═S) substituents is, for example, 2-oxopyrrolidinyl, 2-thioxopyrrolidinyl, 2-oxoimidazolidinyl, 2-thioxoimidazolidinyl, 2-oxopiperidinyl, 2,5-dioxopyrrolidinyl, 2,5-dioxoimidazolidinyl or 2,6-dioxopiperidinyl. Particular heterocyclyl groups are saturated monocyclic 3 to 7 membered heterocyclyls containing 1, 2 or 3 heteroatoms selected from nitrogen, oxygen or sulfur, for example azetidinyl, tetrahydrofuranyl, tetrahydropyranyl, pyrrolidinyl, morpholinyl, tetrahydrothienyl, tetrahydrothienyl 1,1-dioxide, thiomorpholinyl, thiomorpholinyl 1,1-dioxide, piperidinyl, homopiperidinyl, piperazinyl or homopiperazinyl. As the skilled person would appreciate, any heterocycle may be linked to another group via any suitable atom, such as via a carbon or nitrogen atom. Suitably, the term “heterocyclyl”, “heterocyclic” or “heterocycle” will refer to 4, 5, 6 or 7 membered monocyclic rings as defined above. In a particular embodiment, heterocyclyl is tetrahydropyranyl.
The term “heteroaryl” or “heteroaromatic” means an aromatic mono-, bi-, or polycyclic ring incorporating one or more (for example 1-4, particularly 1, 2 or 3) heteroatoms selected from nitrogen, oxygen or sulfur. Examples of heteroaryl groups are monocyclic and bicyclic groups containing from five to twelve ring members, and more usually from five to ten ring members. The heteroaryl group can be, for example, a 5- or 6-membered monocyclic ring or a 9- or 10-membered bicyclic ring, for example a bicyclic structure formed from fused five and six membered rings or two fused six membered rings. Each ring may contain up to about four heteroatoms typically selected from nitrogen, sulfur and oxygen. Typically the heteroaryl ring will contain up to 3 heteroatoms, more usually up to 2, for example a single heteroatom. In one embodiment, the heteroaryl ring contains at least one ring nitrogen atom. The nitrogen atoms in the heteroaryl rings can be basic, as in the case of an imidazole or pyridine, or essentially non-basic as in the case of an indole or pyrrole nitrogen. In general the number of basic nitrogen atoms present in the heteroaryl group, including any amino group substituents of the ring, will be less than five. Suitably, the term “heteroaryl” or “heteroaromatic” will refer to 5 or 6 membered monocyclic hetyeroaryl rings as defined above.
The term “aryl” means a cyclic or polycyclic aromatic ring having from 5 to 12 carbon atoms. The term aryl includes both monovalent species and divalent species. Examples of aryl groups include, but are not limited to, phenyl, biphenyl, naphthyl and the like. Typically, aryl is phenyl.
The term “optionally substituted” refers to either groups, structures, or molecules that are substituted and those that are not substituted. It will be understood that substitutions may only occur at sites where it is chemically feasible to do so.
Where optional substituents are chosen from “one or more” groups it is to be understood that this definition includes all substituents being chosen from one of the specified groups or the substituents being chosen from two or more of the specified groups.
Catalytic processes of the invention
As described hereinbefore, the present invention provides a catalytic process comprising the step of:
The numerous benefits of heterogeneous catalytic systems (wherein the catalyst is provided in the solid state, with the reagent being provided in a liquid or gaseous state) are well documented. As alluded to hereinbefore, although various heterogeneous solidgas catalytic systems for catalytic processes involving C—H bond activation (e.g. alkane dehydrogenation and alkene isomerization) are known,27, 35, 36 they often require high temperatures for their operation. Industrially, this is sub-optimal for a variety of reasons. Not only does the requirement for high temperatures have environmental consequences, but the elevated temperatures can themselves hamper catalytic performance (e.g. by loss of selectivity), as well as shorten the lifetime of the catalyst by thermally-induced decomposition (e.g. by coking). Hence, the poor recyclability of such catalysts, coupled to the high temperatures required for their operation, can result in high operating costs on an industrial scale.
When compared with prior art C—H bond activation catalytic processes, the catalytic processes of the invention offer a number of advantages. Chiefly, the solid-phase compounds of formula (I) have been demonstrated to be catalytically active in catalytic processes involving C—H bond activation at temperatures significantly lower than currently available techniques. In particular, the compounds of formula (I) have been shown to exhibit significant catalytic activity in alkene isomerisation, alkane transfer dehydrogenation, and alkene dimerization reactions at room temperature. Moreover, the compounds of formula (I) exhibit remarkable long-term stability, as well as notable catalytic recyclability.
In an embodiment,
wherein Rx and Ry are each independently selected from hydrogen and (1-4C)alkyl;
In an embodiment, the two heteroatoms of Bd are independently substituted with one or more substituents selected from iso-propyl, tert-butyl, sec-butyl, iso-propoxy, tert-butoxy, sec-butoxy, 6-8 membered carbocyclyl, 6-8 membered heterocyclyl (e.g. tetrahydropyranyl), aryl or adamantyl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl, (1-4C)alkoxy, and —N(Rx)(Ry),
wherein Rx and Ry are each independently selected from hydrogen and (1-4C)alkyl.
In an embodiment, the two heteroatoms of Bd are independently substituted with one or more substituents selected from iso-propyl, tert-butyl, 6-8 membered carbocyclyl, aryl or adamantyl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the two heteroatoms of Bd are independently substituted with one or more substituents selected from iso-propyl, 6-8 membered carbocyclyl, aryl or adamantyl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the two heteroatoms of Bd are independently substituted with one or more substituents selected from iso-propyl, cyclohexyl or aryl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the two heteroatoms of Bd are independently substituted with one or more cyclohexyl substituents, any of which may be substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the two heteroatoms of Bd are each substituted with two cyclohexyl substituents.
In an embodiment, Bd is a bis-phosphine or bis-amine bidentate ligand.
In an embodiment, Bd is a bis-amine bidentate ligand.
In an embodiment, Bd is a bis-amine bidentate ligand selected from ethylenediamine, 1,4-diazadiene, 1,1′-bipyridine, 1,10-phenanthroline and ethylenediaminetetraacetate, wherein one or more of the N atoms is independently optionally substituted with one or more substituents as defined hereinbefore in respect of Bd.
In an embodiment, Bd is a bis-phosphine bidentate ligand. The bis-phosphine bidentate ligand may have a structure according to formula (II) shown below:
wherein
Ra, Ra′, Rb and Rb′ are each independently iso-propyl, tert-butyl, sec-butyl, n-pentyl, iso-pentyl, neo-pentyl, tert-pentyl, sec-pentyl, 3-pentyl, iso-propoxy, tert-butoxy, sec-butoxy, n-pentoxy, iso-pentoxy, neo-pentoxy, tert-pentoxy, sec-pentoxy, 3-pentoxy, 6-8 membered carbocyclyl, 6-8 membered heterocyclyl, aryl or adamantyl, any of which may be optionally substituted with one or more substituents selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy, (1-4C)haloalkyl and —N(Rx)(Ry),
W is a (1-5C)alkylene linking group, wherein one or more of the carbon atoms may be replaced with a heteroatom selected from N, O and S, and wherein W is optionally substituted with one or more groups Rc, wherein each Rc is independently selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy, (1-4C)haloalkyl and aryl,
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (II), wherein W is a (1-5C)alkylene linking group optionally substituted with one or more groups Rc, wherein each Rc is independently (1-4C)alkyl or (1-4C)alkoxy, and/or two groups Rc may be linked, such that when taken with the atoms to which they are attached, they form a phenyl group optionally substituted with one or more substituents selected from halo, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (II), wherein W is a (1-5C)alkylene linking group optionally substituted with one or more groups Rc, wherein each Rc is independently (1-4C)alkyl, and/or two groups Rc may be linked, such that when taken with the atoms to which they are attached, they form a phenyl group optionally substituted with one or more substituents selected from halo and (1-4C)alkyl.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (II), wherein W has any of the following structures:
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (II), wherein W has any of the following structures:
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (II), wherein W is ethylene, propylene, butylene or pentylene.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (II), wherein W is ethylene.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (II), wherein Ra, Ra′, Rb and Rb′ are each independently iso-propyl, tert-butyl, sec-butyl, iso-propoxy, tert-butoxy, sec-butoxy, 6-8 membered carbocyclyl, 6-8 membered heterocyclyl (e.g. tetrahydropyranyl), aryl or adamantyl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl, (1-4C)alkoxy, and N(Rx)(Ry), wherein Rx and Ry are each independently selected from hydrogen and (1-4C)alkyl.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (II), wherein Ra, Ra′, Rb and Rb′ are each independently iso-propyl, tert-butyl, 6-8 membered carbocyclyl, aryl or adamantyl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (II), wherein Ra, Ra′, Rb and Rb′ are each independently iso-propyl, 6-8 membered carbocyclyl, aryl or adamantyl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (II), wherein Ra, Ra′, Rb and Rb′ are each independently iso-propyl, cyclohexyl or aryl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (II), wherein Ra, Ra′, Rb and Rb′ are cyclohexyl, any of which may be substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (II), wherein Ra, Ra′, Rb and Rb′ are cyclohexyl.
Each X is a weakly bound ligand. It will be appreciated by those of skill in the art that the strength of binding between Rh and X has important implications for the catalytic processes of the invention. In particular, it will be appreciated that a weakly bound ligand X is one that can be displaced by the C4-C10 hydrocarbon during step a) of the catalytic process. In an embodiment, each X is independently a ligand weakly bound to Rh via one or more bond, wherein the total energy of coordination of Rh to each X is <130 KJ mol−1. Suitably, each X is independently a ligand weakly bound to Rh via one or more bond, wherein the total energy of coordination of Rh to each X is 5-130 KJ mol−1. More suitably, each X is independently a ligand weakly bound to Rh via one or more bond, wherein the total energy of coordination of Rh to each X is 5-125 KJ mol−1. Yet more suitably, each X is independently a ligand weakly bound to Rh via one or more bond, wherein the total energy of coordination of Rh to each X is 5-122 KJ mol−1. Most suitably, each X is independently a ligand weakly bound to Rh via one or more bond, wherein the total energy of coordination of Rh to each X is 5-118 KJ mol−1.
In an embodiment, each X is hydrogen, an alkane, an alkene or dinitrogen
In an embodiment, each X is an alkane, an alkene or dinitrogen.
In an embodiment, each X is selected from hydrogen, dinitrogen, a linear or branched (2-10C)alkene, a 5-10 membered cycloalkene, a linear or branched (2-10C)alkane and a 5-10 membered cycloalkane, any of which may be optionally substituted with one or more substituents selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy, (1-4C)haloalkyl and —N(Rx)(Ry),
wherein Rx and Ry are each independently selected from hydrogen and (1-4C)alkyl.
In an embodiment, each X is selected from hydrogen, dinitrogen, a linear or branched (2-10C)alkene, a monounsaturated 5-10 membered cycloalkene, a branched (2-10C)alkane and a 5-10 membered cycloalkane, any of which may be optionally substituted with one or more substituents selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy and (1-4C)haloalkyl.
In an embodiment, each X is selected from hydrogen, dinitrogen, a linear or branched (2-8C)alkene, a monounsaturated 5-8 membered cycloalkene, a branched (6-10C)alkane and a 5-10 membered cycloalkane, any of which may be optionally substituted with one or more substituents selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy and (1-4C)haloalkyl.
In an embodiment, each X is selected from dinitrogen, a linear or branched (2-10C)alkene, a 5-10 membered cycloalkene, a linear or branched (2-10C)alkane and a 5-10 membered cycloalkane, any of which may be optionally substituted with one or more substituents selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy, (1-4C)haloalkyl and —N(Rx)(Ry),
wherein Rx and Ry are each independently selected from hydrogen and (1-4C)alkyl.
In an embodiment, each X is selected from dinitrogen, a linear or branched (2-10C)alkene, a monounsaturated 5-10 membered cycloalkene, a branched (2-10C)alkane and a 5-10 membered cycloalkane, any of which may be optionally substituted with one or more substituents selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy and (1-4C)haloalkyl.
In an embodiment, each X is selected from dinitrogen, a linear or branched (2-8C)alkene, a monounsaturated 5-8 membered cycloalkene, a branched (6-10C)alkane and a 5-10 membered cycloalkane, any of which may be optionally substituted with one or more substituents selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy and (1-4C)haloalkyl.
Exemplary linear alkenes include ethene, propene, butene and hexene.
Exemplary 5-10 membered cycloalkenes include cycloheptene and cyclooctene. Other exemplary 5-10 membered cycloalkenes include norbornene.
Exemplary 5-10 membered cycloalkanes are illustrated below:
In an embodiment, each X is selected from hydrogen, ethene, propene, butene, hexane, cyclooctene and norbornane. Suitably, each X is ethene or norbornane.
In an embodiment, each X is selected from ethene, propene, butene, hexene and norbornane. Suitably, each X is ethene or norbornane.
It will be understood that the nature of bonding between Rh and X will depend on the nature of X. When X is ethene, each ethene ligand may be η2 coordinated to Rh. When X is norbornane, the norbornane ligand is coordinated to Rh by a 3-centre 2-electron sigma interaction between the C—H bond of the norbornane and the metal centre.
It will be understood that the value of n depends on the nature of X. For smaller X ligands (e.g. ethene or hydrogen), Rh can accommodate two or three X ligands (e.g. n=2 or 3). For larger X ligands (e.g. norbornane), Rh can accommodate only one X ligand (e.g. n=1). Suitably, n is 1 or 2.
In an embodiment, Q is boron or aluminium.
In an embodiment, Q is boron.
In an embodiment, each Ar is either i) a phenyl group substituted at the 3-, 4- and/or 5-position with one or more substituents selected from halo (1-3C)alkyl and (1-3C)haloalkyl, or ii) a (1-3C)alkoxy group substituted with one or more substituents selected from halo (1-3C)alkyl and (1-3C) haloalkyl.
In an embodiment, each Ar is either i) a phenyl group substituted at the 3- and/or 5-position with one or more substituents selected from fluoro, chloro, (1-3C)alkyl and (1-3C)haloalkyl, or ii) a (1-3C)alkoxy group substituted with one or more substituents selected from fluoro, chloro and (1-2C)haloalkyl.
In an embodiment, each Ar is either i) a phenyl group substituted at the 3- and/or 5-position with one or more substituents selected from fluoro, chloro, (1-2C)alkyl and (1-2C)fluoroalkyl, or ii) a (1-2C)alkoxy group substituted with one or more substituents selected from fluoro, chloro and (1-2C)haloalkyl.
In an embodiment, each Ar is a phenyl group substituted at the 3-, 4- and/or 5-position with one or more substituents selected from (1-3C)alkyl and (1-3C)haloalkyl.
In an embodiment, each Ar is a phenyl group substituted at the 3- and/or 5-position with one or more substituents selected from (1-3C)alkyl and (1-3C)haloalkyl.
In an embodiment, each Ar is a phenyl group substituted at the 3- and/or 5-position with one or more substituents selected from (1-2C)alkyl and (1-2C)fluoroalkyl.
In an embodiment, each Ar is a phenyl group substituted at both the 3- and 5-position with a substituent selected from (1-2C)alkyl and (1-2C)fluoroalkyl.
In an embodiment, each Ar is a phenyl group substituted at both the 3- and 5-position with trifluoromethyl.
In an embodiment, [QAr4] has any of the following structures:
wherein Rp is fluoro, chloro, difluoromethyl or trifluromethyl. Suitably, Rp is fluoro, chloro or trifluromethyl.
In a particular embodiment, the compound of formula (I) has any of the following structures:
wherein ‘Cy’ denotes cyclohexyl,
In a particular embodiment, the compound of formula (I) has any of the following structures:
wherein ‘Cy’ denotes cyclohexyl and ‘ArF’ denotes 3,5-(CF3)2C6H3.
In a particular embodiment, the compound of formula (I) has either of the following structures:
wherein ‘Cy’ denotes cyclohexyl and ‘ArF’ denotes 3,5-(CF3)2C6H3.
In an embodiment, the compound of formula (I) is a solid. Suitably, the compound of formula (I) is crystalline.
In an embodiment, the compound of formula (I) is unsupported. By virtue of their crystalline morphology, the compounds of formula (I) are themselves suitable for direct use in heterogeneous catalytic systems, without the need for being supported on a separate solid support (e.g. silica or alumina).
In an embodiment, the compound of formula (I) is
wherein ‘Cy’ denotes cyclohexyl and ‘ArF’ denotes 3,5-(CF3)2C6H3, and wherein the compounds has octahedral crystal morphology. The space groups is 02/c (No. 15 International Tables). Suitably, the X-ray powder diffraction pattern for the compound exhibits strong peaks at 2theta=9.1953 and 19.1186°.
In an embodiment, the compound of formula (I) is
wherein ‘Cy’ denotes cyclohexyl and ‘ArF’ denotes 3,5-(CF3)2C6H3, and wherein the compounds has hexagonal crystal morphology. The space groups is P6322 (No. 182 International Tables). Suitably, the X-ray powder diffraction pattern for the compound exhibits strong peaks at 2theta=3.9514 and 6.8133°.
In an embodiment, the C4-C10 hydrocarbon is in the form of a liquid or gas, and the catalytic process is conducted in the heterogeneous state (the compound of formula (I) being a solid).
The concept of C—H bond activation will be readily understood by one of ordinary skill in the art. In particular, it will be appreciated that C—H bond activation refers to the cleavage of unreacted C—H bonds in hydrocarbons by transition metal complexes to form products containing one or more M-C bond (when M is the transition metal). A variety of catalytic processes employing transition metal-containing catalysts proceed via an initial step of activation of a C-H bond within a hydrocarbon substrate. Such catalytic processes include, but are not limited to, alkene isomerisation, alkane transfer dehydrogenation and alkene dimerization.
In an embodiment, the C4-C10 hydrocarbon is an alkene comprising one or more C═C bonds, and step a) results in the migration of the one or more C═C bonds within the alkene. In such embodiments, the catalytic process is an alkene isomerisation process.
It will be appreciated that within the alkene isomerisation process, the alkene may contain one or more double bonds. When the alkene contains more than one double bond, step a) may result in the migration of one or more double bonds. It will also be understood that the alkene may be linear or branched, and may be substituted with one or more substituents selected from halo, oxo, hydroxyl and amino. Suitably, the alkene is a terminal alkene (e.g. 1-butene) or an internal alkene (e.g. 2-butene). Depending on the nature of the 04-C10 hydrocarbon, step a) may result in the formation of a terminal alkene, an internal alkene, or a mixture of both.
In an embodiment, the C4-C10 hydrocarbon is an alkene comprising one or more C═C bonds, and step a) results in the migration of the one or more C═C bonds within the alkene, wherein the alkene is a C4-C8 alkene.
In an embodiment, the C4-C10 hydrocarbon is an alkene comprising one or more C═C bonds, and step a) results in the migration of the one or more C═C bonds within the alkene, wherein the alkene is selected from 1-butene and 2-butene.
In an embodiment, the C4-C10 hydrocarbon is 1-butene and the process results in the conversion of the 1-butene to 2-butene. The process results in a mixture of cis and trans 2-butene isomers.
In an embodiment, the catalytic process is an alkene isomerisation process and step a) is conducted at a temperature of 0-100° C. Suitably, step a) is conducted at a temperature of 0-50° C. More suitably, step a) is conducted at a temperature of 0-30° C. Most suitably, step a) is conducted at a temperature of 18-30° C.
In an embodiment, the catalytic process is an alkene isomerisation process, wherein the molar ratio of the compound of formula (I) to the C4-C10 hydrocarbon in step a) is 1:1 to 1:100000. Suitably, the molar ratio of the compound of formula (I) to the C4-C10 hydrocarbon in step a) is 1:40 to 1:1000.
In another embodiment, the C4-C10 hydrocarbon is an alkane, and step a) is conducted in the presence of a hydrogen acceptor, and wherein step a) results in the dehydrogenation of the alkane and the hydrogenation of the hydrogen acceptor. In such embodiments, the catalytic process is an alkane transfer dehydrogenation process.
It will be appreciated that within the alkane transfer dehydrogenation process, the alkane may be linear or branched, and may be substituted with one or more substituents selected from halo, oxo, hydroxyl and amino. The hydrogen acceptor may be any suitable hydrogen acceptor. Suitably, the hydrogen acceptor is an alkene (e.g. ethene).
In an embodiment, the C4-C10 hydrocarbon is a C4-C5 alkane and the hydrogen acceptor is a C2-C6 alkene.
In an embodiment, the C4-C10 hydrocarbon is butane the hydrogen acceptor is ethene, and where step a) results in the conversion of the butane into 1-butene or 2-butene. It will be appreciated that when butane is dehydrogenated to 1-butene, the 1-butene may subsequently undergo isomerisation to 2-butene (as described above).
In an embodiment, step a) of the transfer dehydrogenation process is conducted at a temperature of 0-100° C. Suitably, step a) is conducted at a temperature of 0-50° C. More suitably, step a) is conducted at a temperature of 0-30° C. Most suitably, step a) is conducted at a temperature of 18-30° C.
In an embodiment, the catalytic process is an alkane transfer dehydrogenation process, wherein the molar ratio of the C4-C10 hydrocarbon to the hydrogen acceptor is 0.1:1 to 1:6. Suitably, the molar ratio of the C4-C10 hydrocarbon to the hydrogen acceptor is 1:1 to 1:6. More suitably, molar ratio of the C4-C10 hydrocarbon to the hydrogen acceptor is 1:1.5 to 1:2.5
In another embodiment, step a) results in the dimerization of two molecules of the C4-C10 hydrocarbon, wherein the C4-C10 hydrocarbon is an alkene. In such embodiments, the catalytic process is an alkene dimerization process.
In an embodiment, the C4-C10 hydrocarbon is a C2-C5 alkene. Suitably, the C4-C10 hydrocarbon is ethene and the process results in the generation of 1-butene and/or 2-butene.
As described hereinbefore, the present invention also provides a compound having a structure according to formula (Ia) shown below:
wherein
As alluded to hereinbefore, although various heterogeneous solidgas catalytic systems for catalytic processes involving C—H bond activation (e.g. alkane dehydrogenation and alkene isomerization) are known,27, 35, 36 they often require high temperatures for their operation. Industrially, this is sub-optimal for a variety of reasons. Not only does the requirement for high temperatures have environmental consequences, but the elevated temperatures can themselves shorten the lifetime of the catalyst by thermally-induced decomposition (e.g. by coking). Hence, the poor recyclability of such catalysts, coupled to the high temperatures required for their operation, can result in high operating costs on an industrial scale.
When compared with prior art catalysts useful in catalytic processes involving C—H bond activation the compounds of the invention offer a number of advantages. Chiefly, the compounds of formula (Ia) have been demonstrated to be catalytically active in catalytic processes involving C—H bond activation at temperatures significantly lower than currently available techniques. In particular, the compounds of formula (Ia) have been shown to exhibit significant catalytic activity in alkene isomerisation, alkane transfer dehydrogenation, and alkene dimerization reactions at room temperature. Moreover, the compounds of formula (Ia) exhibit remarkable long-term stability, as well as notable catalytic recyclability.
In an embodiment, Bd is a bidentate ligand bonded to Rh via two heteroatoms independently selected from P, N and S, wherein the two heteroatoms are independently optionally substituted with one or more substituents selected from iso-propyl, tert-butyl, sec-butyl, n-pentyl, iso-pentyl, neo-pentyl, tert-pentyl, sec-pentyl, 3-pentyl, iso-propoxy, iso-butoxy, tert-butoxy, sec-butoxy, n-pentoxy, iso-pentoxy, neo-pentoxy, tert-pentoxy, sec-pentoxy, 3-pentoxy, 6-8 membered carbocyclyl, 6-8 membered heterocyclyl, aryl or adamantyl, any of which may be optionally substituted with one or more substituents selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy, (1-4C)haloalkyl and —N(Rx)(Ry),
wherein Rx and Ry are each independently selected from hydrogen and (1-4C)alkyl;
wherein Rv and Rw are each independently selected from hydrogen and (1-4C)alkyl;
In an embodiment, the two heteroatoms of Bd are independently substituted with one or more substituents selected from iso-propyl, tert-butyl, sec-butyl, iso-propoxy, tert-butoxy, sec-butoxy, 6-8 membered carbocyclyl, 6-8 membered heterocyclyl (e.g. tetrahydropyranyl), aryl or adamantyl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl, (1-4C)alkoxy, and —N(Rx)(Ry),
wherein Rx and Ry are each independently selected from hydrogen and (1-4C)alkyl.
In an embodiment, the two heteroatoms of Bd are independently substituted with one or more substituents selected from iso-propyl, tert-butyl, 6-8 membered carbocyclyl, aryl or adamantyl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the two heteroatoms of Bd are independently substituted with one or more substituents selected from iso-propyl, 6-8 membered carbocyclyl, aryl or adamantyl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the two heteroatoms of Bd are independently substituted with one or more substituents selected from iso-propyl, cyclohexyl or aryl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the two heteroatoms of Bd are independently substituted with one or more cyclohexyl substituents, any of which may be substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the two heteroatoms of Bd are each substituted with two cyclohexyl substituents.
In an embodiment, Bd is a bis-phosphine or bis-amine bidentate ligand.
In an embodiment, Bd is a bis-amine bidentate ligand.
In an embodiment, Bd is a bis-amine bidentate ligand selected from ethylenediamine, 1,4-diazadiene, 1,1′-bipyridine, 1,10-phenanthroline and ethylenediaminetetraacetate, wherein one or more of the N atoms is independently optionally substituted with one or more substituents as defined hereinbefore in respect of Bd.
In an embodiment, Bd is a bis-phosphine bidentate ligand. The bis-phosphine bidentate ligand may have a structure according to formula (IIa) shown below:
wherein
Ra, Ra′, Rb and Rb′ are each independently iso-propyl, tert-butyl, sec-butyl, n-pentyl, iso-pentyl, neo-pentyl, tert-pentyl, sec-pentyl, 3-pentyl, iso-propoxy, tert-butoxy, sec-butoxy, n-pentoxy, iso-pentoxy, neo-pentoxy, tert-pentoxy, sec-pentoxy, 3-pentoxy, 6-8 membered carbocyclyl, 6-8 membered heterocyclyl, aryl or adamantyl, any of which may be optionally substituted with one or more substituents selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy, (1-4C)haloalkyl and —N(Rx)(Ry),
W is a (1-5C)alkylene linking group, wherein one or more of the carbon atoms may be replaced with a heteroatom selected from N, O and S, and wherein W is optionally substituted with one or more groups Rc,
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (IIa), wherein W is a (1-5C)alkylene linking group optionally substituted with one or more groups Rc, wherein each Rc is independently (1-4C)alkyl or (1-4C)alkoxy, and/or two groups Rc may be linked, such that when taken with the atoms to which they are attached, they form a phenyl group optionally substituted with one or more substituents selected from halo, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (IIa), wherein W is a (1-5C)alkylene linking group optionally substituted with one or more groups Rc, wherein each Rc is independently (1-4C)alkyl, and/or two groups Rc may be linked, such that when taken with the atoms to which they are attached, they form a phenyl group optionally substituted with one or more substituents selected from halo and (1-4C)alkyl.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (II), wherein W has any of the following structures:
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (IIa), wherein W has any of the following structures:
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (II), wherein W is ethylene, propylene, butylene or pentylene.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (IIa), wherein W is ethylene.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (IIa), wherein Ra, Ra′, Rb and Rb′ are each independently iso-propyl, tert-butyl, sec-butyl, iso-propoxy, tert-butoxy, sec-butoxy, 6-8 membered carbocyclyl, 6-8 membered heterocyclyl (e.g. tetrahydropyranyl), aryl or adamantyl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl, (1-4C)alkoxy, and —N(Rx)(Ry),
wherein Rx and Ry are each independently selected from hydrogen and (1-4C)alkyl.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (IIa), wherein Ra, Ra′, Rb and Rb′ are each independently iso-propyl, tert-butyl, 6-8 membered carbocyclyl, aryl or adamantyl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (IIa), wherein Ra, Ra′, Rb and Rb′ are each independently iso-propyl, 6-8 membered carbocyclyl, aryl or adamantyl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (IIa), wherein Ra, Ra′, Rb and Rb′ are each independently iso-propyl, cyclohexyl or aryl, any of which may be optionally substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (IIa), wherein Ra, Ra′, Rb and Rb′ are cyclohexyl, any of which may be substituted with one or more substituents selected from halo, hydroxyl, (1-4C)alkyl and (1-4C)alkoxy.
In an embodiment, the bis-phosphine bidentate ligand has a structure according to formula (IIa), wherein Ra, Ra′, Rb and Rb′ are cyclohexyl.
Each X is a weakly bound ligand. It will be appreciated by those of skill in the art that the strength of binding between Rh and X has important implications for the catalytic activity of the compounds. In particular, it will be appreciated that a weakly bound ligand X is one that can be displaced by the C4-C10 hydrocarbon used during step a) of the catalytic process of the invention. In an embodiment, each X is independently a ligand weakly bound to Rh via one or more bond, wherein the total energy of coordination of Rh to each X is 5-130 KJ mol−1. More suitably, each X is independently a ligand weakly bound to Rh via one or more bond, wherein the total energy of coordination of Rh to each X is 5-125 KJ mol−1. Yet more suitably, each X is independently a ligand weakly bound to Rh via one or more bond, wherein the total energy of coordination of Rh to each X is 5-122 KJ mol−1. Most suitably, each X is independently a ligand weakly bound to Rh via one or more bond, wherein the total energy of coordination of Rh to each X is 5-118 KJ mol−1.
In an embodiment, each X is hydrogen, an alkane, an alkene or dinitrogen.
In an embodiment, each X is an alkane, an alkene or dinitrogen.
In an embodiment, each X is selected from hydrogen, dinitrogen, a linear or branched (2-10C)alkene, a 5-10 membered cycloalkene, a linear or branched (6-10C)alkane and a 8-10 membered cycloalkane, any of which may be optionally substituted with one or more substituents selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy, (1-4C)haloalkyl and N(Rx)(Ry),
wherein Rx and Ry are each independently selected from hydrogen and (1-4C)alkyl
In an embodiment, each X is selected from hydrogen, dinitrogen, a linear or branched (2-10C)alkene, a monounsaturated 5-10 membered cycloalkene, a branched (6-10C)alkane and a 8-10 membered cycloalkane, any of which may be optionally substituted with one or more substituents selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy and (1-4C)haloalkyl.
In an embodiment, each X is selected from hydrogen, dinitrogen, a linear or branched (2-8C)alkene, a monounsaturated 5-8 membered cycloalkene, a branched (6-10C)alkane and a 8-10 membered cycloalkane, any of which may be optionally substituted with one or more substituents selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy and (1-4C)haloalkyl.
In an embodiment, each X is selected from dinitrogen, a linear or branched (2-10C)alkene, a 5-10 membered cycloalkene, a linear or branched (6-10C)alkane and a 8-10 membered cycloalkane, any of which may be optionally substituted with one or more substituents selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy, (1-4C)haloalkyl and —N(Rx)(Ry),
wherein Rx and Ry are each independently selected from hydrogen and (1-4C)alkyl
In an embodiment, each X is selected from dinitrogen, a linear or branched (2-10C)alkene, a monounsaturated 5-10 membered cycloalkene, a branched (6-10C)alkane and a 8-10 membered cycloalkane, any of which may be optionally substituted with one or more substituents selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy and (1-4C)haloalkyl.
In an embodiment, each X is selected from dinitrogen, a linear or branched (2-8C)alkene, a monounsaturated 5-8 membered cycloalkene, a branched (6-10C)alkane and a 8-10 membered cycloalkane, any of which may be optionally substituted with one or more substituents selected from halo, oxo, hydroxyl, (1-4C)alkyl, (2-4C)alkenyl, (2-4C)alkynyl, (1-4C)alkoxy and (1-4C)haloalkyl.
Exemplary linear alkenes include ethene, propene, butene and hexene.
Exemplary 5-10 membered cycloalkenes include cycloheptene and cyclooctene.
Exemplary 8-10 membered cycloalkanes are illustrated below:
In an embodiment, each X is selected from hydrogen, ethene, propene, butane, hexane and cyclooctene.
In an embodiment, each X is selected from ethene, propene, butene and hexene. Suitably, each X is ethene.
It will be understood that the nature of bonding between Rh and X will depend on the nature of X. When X is ethene, each ethene ligand may be rig coordinated to Rh. When X is an alkane, the alkane ligand is coordinated to Rh by a 3-centre 2-electron sigma interaction between the CH bond of the alkane and the metal centre.
It will be understood that the value of n depends on the nature of X. For smaller X ligands (e.g. hydrogen and ethene), Rh can accommodate two or three X ligands (e.g. n=2 or 3). For larger X ligands (e.g. butane), Rh can accommodate only one X ligand (e.g. n=1). Suitably, n is 1 or 2.
In an embodiment, Q is boron or aluminium.
In an embodiment, Q is boron.
In an embodiment, each Ar is either i) a phenyl group substituted at the 3-, 4- and/or 5-position with one or more substituents selected from halo (1-3C)alkyl and (1-3C)haloalkyl, or ii) a (1-3C)alkoxy group substituted with one or more substituents selected from halo (1-3C)alkyl and (1-3C) haloalkyl.
In an embodiment, each Ar is either i) a phenyl group substituted at the 3-, and/or 5-position with one or more substituents selected from fluoro, chloro, (1-3C)alkyl and (1-3C)haloalkyl, or ii) a (1-3C)alkoxy group substituted with one or more substituents selected from fluoro, chloro and (1-2C)haloalkyl.
In an embodiment, each Ar is either i) a phenyl group substituted at the 3-, and/or 5-position with one or more substituents selected from fluoro, chloro, (1-2C)alkyl and (1-2C)fluoroalkyl, or ii) a (1-2C)alkoxy group substituted with one or more substituents selected from fluoro, chloro and (1-2C)haloalkyl.
In an embodiment, each Ar is a phenyl group substituted at the 3-, 4- and/or 5-position with one or more substituents selected from (1-3C)alkyl and (1-3C)haloalkyl.
In an embodiment, each Ar is a phenyl group substituted at the 3- and/or 5-position with one or more substituents selected from (1-3C)alkyl and (1-3C)haloalkyl.
In an embodiment, each Ar is a phenyl group substituted at the 3- and/or 5-position with one or more substituents selected from (1-2C)alkyl and (1-2C)fluoroalkyl.
In an embodiment, each Ar is a phenyl group substituted at both the 3- and 5-position with a substituent selected from (1-2C)alkyl and (1-2C)fluoroalkyl.
In an embodiment, each Ar is a phenyl group substituted at both the 3- and 5-position with trifluoromethyl.
In an embodiment, [QAr4] has any of the following structures:
wherein Rp is fluoro, chloro, difluoromethyl or trifluromethyl. Suitably, Rp is fluoro, chloro or trifluromethyl.
In a particular embodiment, the compound of formula (I) has any of the following structures:
wherein ‘Cy’ denotes cyclohexyl and ‘ArF’ denotes 3,5-(CF3)2C6H3.
In a particular embodiment, the compound of formula (Ia) has any of the following structures:
wherein ‘Cy’ denotes cyclohexyl and ‘ArF’ denotes 3,5(CF3)2C6H3.
In a particular embodiment, the compound of formula (Ia) has either of the following structures:
wherein ‘Cy’ denotes cyclohexyl and ‘ArF’ denotes 3,5-(CF3)2C6H3.
In an embodiment, the compound of formula (Ia) is a solid. Suitably, the compound of formula (Ia) is crystalline.
In an embodiment, the compound of formula (Ia) is unsupported. By virtue of their crystalline morphology, the compounds of formula (Ia) are themselves suitable for direct use in heterogeneous catalytic systems, without the need for being supported on a separate solid support (e.g. silica or alumina).
In an embodiment, the compound of formula (Ia) is
wherein ‘Cy’ denotes cyclohexyl and ‘ArF’ denotes 3,5-(CF3)2C6H3, and wherein the compounds has octahedral crystal morphology. The space groups is C2/c (No. 15 International Tables). Suitably, the X-ray powder diffraction pattern for the compound exhibits strong peaks at 2theta=9.1953 and 19.1186°.
In an embodiment, the compound of formula (Ia) is
wherein ‘Cy’ denotes cyclohexyl and ‘ArF’ denotes 3,5-(CF3)2C6H3, and wherein the compounds has hexagonal crystal morphology. The space groups is P6322 (No. 182 International Tables). Suitably, the X-ray powder diffraction pattern for the compound exhibits strong peaks at 2theta=3.9514 and 6.8133°.
In another aspect, the present invention provides a compound having a structure according to formula (Ia) described hereinbefore, wherein Bd, n, Q and Ar have any of the definitions appearing hereinbefore, and each X is independently a ligand that is weakly bound to Rh via one or more bond, each bond having a bond energy of <130 KJmol−1, with the proviso that X is not norbornane or n-pentane.
The compounds of the invention can be prepared by any suitable means known in the art.
In one aspect, the compounds of formula (Ia) are prepared by a process comprising the following steps:
wherein
It will be appreciated that Bd, Q, Ar and X may have any of the definitions appearing hereinbefore in respect of the compounds of formula (Ia).
Suitably, the compound of formula (Ia′) is a solid, and step b) is conducted in the solid phase (i.e. not in solution). More suitably, in step b), X is provided as a gas.
In a particular embodiment, the compound of formula (Ia) is:
wherein ‘Cy’ denotes cyclohexyl and ‘ArF’ denotes 3,5-(CF3)2C6H3;
and step b) comprises contacting the compound of formula (Ia′) with ethene. Such a process results in the formation of [1-(ethene)2][BArF4] having octahedral crystal morphology.
In a particular embodiment, the compound of formula (Ia) is:
wherein ‘Cy’ denotes cyclohexyl and ‘ArF’ denotes 3,5-(CF3)2C6I−13;
The person skilled in the art will be able to select appropriate reaction conditions (e.g. temperatures, pressures, and durations) for carrying out the processes described herein.
In another aspect, the present invention provides a compound of formula (Ia) obtainable, obtained or directly obtained by a process described herein.
Examples of the invention will now be described, for the purpose of illustration only, with reference to the accompanying figures, in which:
All manipulations (unless otherwise stated) were performed under an atmosphere of argon, using standard Schlenk techniques on a dual vacuum/inlet manifold or by employment of an MBraun glovebox. Glassware was dried in an oven at 130° C. overnight prior to use. Pentane, hexane and CH2Cl2 were dried using an MBraun SPS-800 solvent purification system and degassed by three freeze-pump-thaw cycles. CD2Cl2 and C6H5F were both dried by stirring over CaH2 overnight before being vacuum distilled and subsequently degassed by three freeze-pump-thaw cycles. 1,2-F2C6H4 was stirred over Al2O3 for two hours then over CaH2 overnight overnight before being vacuum distilled and subsequently degassed by three freeze-pump-thaw cycles. Ethylene, propylene and but-1-ene were all supplied by CK gases. Propylene-d3 was supplied by Cambridge isotopes laboratory.
Solution NMR data were collected on either a Brucker AVD 500 MHz or a Bruker Ascend 400 MHz spectrometer at room temperature unless otherwise started. Non-deuterated solvents were locked to standard CD2Cl2 solutions. Residual protio solvent resonances were used as a reference for 1H NMR spectra. A small amount of CD2Cl2 was added as a reference for 2H{1H} NMR spectra. 31P{H} NMR spectra were referenced externally to 85% H3PO4. All chemical shifts (δ) are quoted in ppm and coupling constants in Hz.
1H/13C solid state NMR (SSNMR) spectra (including two dimensional measurements) were obtained on a Bruker Avance III HD spectrometer equipped with a 9.4 Tesla magnet, operating at 399.9 MHz for 1H and 100.6 MHz for 13C using 4 mm O.D. rotors containing approximately 70 mg of sample and a MAS rate of 10 kHz. Powdered microcrystalline samples were prepared by grinding using the back of a spatula in a glovebox and subsequently loaded into 4 mm rotors. Hydrogenation and deuteration reactions were undertaken by exposing the open rotors in a J. Young's flask to an atmosphere (2 atm) of H2/D2 respectively before removal of the atmosphere and capping the rotors in a glovebox. For 13C CP/MAS a sequence with a variable X-amplitude spin-lock pulse1 and spinal64 proton decoupling was used. 4500 transients were acquired using a contact time of 2.5 ms, an acquisition time of 25 ms (2048 data points zero filled to 32 K) and a recycle delay of 2 s. All 13C spectra were referenced to adamantane (the upfield methine resonance was taken to be at δ=29.5 ppm2 on a scale where δ(TMS)=0 ppm as a secondary reference. For the fslg-HETCOR,3 128 transients (2048 data points in F2) and 80 increments in F1 (zero filled to 4k×1k) were acquired with a contact time 0.4 ms and a recycle delay of 5 s. 31 P{1H} spectra were reference externally to 85% H3PO4. Low temperature measurements were undertaken using standard Bruker variable temperature set-up.
Gas phase 1H NMR spectroscopy was carried out using a Bruker Ascend 400 MHz spectrometer. The T1 delay was set to 1 s, and this has been previously shown to allow for the accurate comparison of integrals. Samples were loaded into a high-pressure NMR tube sealed with a Teflon stopcock, before being transferred to a Schlenk vacuum line, evacuated and then loaded with the gaseous reagents (via a custom made glass T-piece adaptor). The spectrometer was locked and shimmed to a separate CD2Cl2 sample in a similar bore tube, the sample was then replaced and spectra run. For isomerisation catalytic runs the machine was locked and shimmed before the gaseous reagents were added (full experimental details of isomerization catalysis are below).
Electrospray ionisation mass spectrometry (ESI-MS) was carried out using a Bruker MicrOTOF instrument directly connected to a modified Innovative Technology glovebox.4 Typical acquisition parameters were used (sample flow rate: 4 μL min−1, nebuliser gas pressure: 0.4 bar, drying gas: Argon at 333 K flowing at 4 L min−1, capillary voltage: 4.5 kV, exit voltage: 60 V). The spectrometer was calibrated using a mixture of tetraalkyl ammonium bromides [N(CnH2n+1)4]Br (n=2-8, 12, 16 and 18). Samples were diluted to a concentration of 1×10−6 M in the appropriate solvent before sampling by ESI-MS.
Single crystal X-ray diffraction data for all samples were collected as follows: a typical crystal was mounted on a MiTeGen Micromounts using perfluoropolyether oil and cooled rapidly to 150 K in a stream of nitrogen gas using an Oxford Cryosystems Cryostream unit.5 Data were collected with an Agilent SuperNova diffractometer (Cu Kα radiation, λ=1.54180 Å). Raw frame data were reduced using CrysAlisPro.6,7 The structures were solved using SuperFlip8 and refined using full-matrix least squares refinement on all F2 data using the CRYSTALS program suite.9, 10 In general distances and angles were calculated using the full covariance matrix. Dihedral angles were calculated using PLATON.11
Isomerisation runs were carried out in the gas phase by loading a high pressure NMR tube (of known volume) with a crystalline sample of the catalyst in an argon-filled glovebox. The tubes were sealed by a Teflon stopcock and transferred to a Schlenk line fitted with a custom-built glass T-piece adaptor, allowing for exposure to vacuum/argon on one side, and the reagent gas on the other side. The T-piece and connecting tubing were thrice pumped and refilled with argon, then thrice pumped and refilled with but-1-ene, before being evacuated (<1×10−2 mbar) and subsequently opening the Teflon stopcock on the NMR tube (thus exposing the argon-filled tube to dynamic vacuum). During this final evacuation the NMR machine was prepared by locking and shimming to a sample of CD2Cl2 in a similar bore NMR tube. The sample was then refilled with but-1-ene gas as a timer was simultaneously started. The tube was sealed and transferred to the NMR machine as quickly as possible. The first data collection was immediately started. The extent of conversion was measured by the comparison of the integral of the two alkene resonances of but-2-ene and the alkyl CH2 resonance of but-1-ene. These have been previously shown to be comparable by gas phase NMR. TON and TOF are calculated assuming that all site are equally catalytically active, and are therefore, a minimum number. Intuitively surface sites would be more active than those at the centre of the bulk by a simple mass transit argument.
One Schlenk flask was charged with [Rh(COD)2][BArF4] (500 mg, 0.423 mmol) and another was filled with Cy2PCH2CH2PCy2 (180 mg, 0.426 mmol). Both solids were dissolved in CH2Cl2 (30 ml each) and the phosphine was added to [Rh(COD)2][BArF4] with vigorous stirring. The solution was allowed to stir for one hour before the solvent was removed in vacuo. The subsequent solid was washed with pentane (3×20 ml) before being taken up in C6H5F (30 ml) and filtered via cannula into a Young's flask. The solution was freeze-pump-thaw degassed three times then H2 gas was added (1 bar). The solution was allowed to stir for four hours before the H2 and solvent was removed in vacuo. The remaining solidwas washed with pentane (3×20m1) then taken up in CH2Cl2 (50 ml) and filtered via cannula into a Schlenk flask. This solution was stirred vigorously and an excess of norbornadiene was added (0.6 ml, 5.904 mmol) and the solution darkened over 15 minutes to a blood-orange red. The solvent was removed in vacuo and excess norbornadiene and C6H5F were removed by washing with pentane (3×20 ml) before the resultant solid was taken up in the minimum volume of CH2Cl2 and filtered into a Young's crystallization tube and layered with pentane. Yield 370 mg (59%). [Rh(Cy2PCH2CH2PCy2)(η2:η2-C7H8)][BArF4]. Hydrogenation (1 atm) of a crystalline sample of [Rh(Cy2PCH2CH2PCy2)(η2:η2-C7H8)][BArF4] led to the quantitative formation of [1-NBA][BArF4] after five minutes. The crystalline sample goes opaque but there is little other colour change.
31P{1H} SS-NMR (162 MHz, 10 kHz spin rate): δ 110.5 (two overlapping d, JRh-P1=207 Hz, JRh-P2=216 Hz). 13C{1H} SS-NMR (101 MHz, 10 kHz spin rate): δ 163.18 (br, BArF4), 134.54 (br, BArF4), 129.80 (br, BArF4), 124.30 (br, BArF4), 118.19 (br, BArF4), 115.84 (br, BArF4), 43.71, 39.65, 38.98, 35.95, 35.34, 31.86, 31.20, 30.17, 29.01, 26.90, 25.33, 20.69 (multiple aliphatic resonances). 1H projection from 1H/13C Frequency Switched LeeGoldburg HECTOR SS-NMR: δ 8.09 (sh), 7.10 (m, br), 0.83 (s), −1.82 (w). 13C projection from 1H/13C Frequency Switched LeeGoldburg HECTOR SS-NMR: δ 134.80, 130.00, 118.60, 116.00, 44.10, 39.50, 36.00, 30.70, 27.40, 25.50, 21.40. Elemental analysis found (calculated): C 52.46 (52.55) H 4.80 (4.89)
A crystalline sample of [(Cy2PCH2CH2FCy2)Rh(η6-F2C6H4)][BArF4] ([1-C6H4F2][BArF4]13) (25 mg, 0.0166 mmol) was taken up in CD2Cl2 (0.5 ml) in a high pressure NMR tube. This was freeze-pump-thaw degassed (<1×10−2 mbar) three times before ethylene gas (1 bar) was added. An immediate darkening of the yellow solution to orange occurred. 31P{1H} NMR spectroscopy indicated that near quantitative conversion to [1-(ethene)2][BArF4] had occurred after 15 minutes (
To an orange sample of crystalline [1-NBA][BArF4] (25 mg, 0.0168 mmol) in an evacuated (<1×10−2 mbar) J Young's flask (c. 50 ml) ethylene gas (1 bar, 298 K) is added and left standing overnight. Little colour change is observed, though the crystals take on the appearance of liquid on the surface assumed to be norbornane. It is not possible to remove the residual norbornane (attempts to do so by washing with pentane did not work), however the synthesis goes in >95% yield by 31P{1H} solid state NMR spectroscopy and 31P{1H} solution NMR spectroscopy when dissolved up in CD2Cl2 (the only other signal being due to an uncharacterised decomposition product, which mass spectroscopic evidence suggests a product of CH2Cl2 activation). After 16 hours in CD2Cl2 the compound decomposes to a range of products. Dissolving the product in difluorobenzene results in the formation of [1-C6H4F2][BArF4].
To an orange sample of crystalline [1-NBA][BArF4] (100 mg, 67.3 μmol) in an evacuated (<1×10−2 mbar) J Young's flask (c. 50 ml) ethylene gas (1 bar, 298 K) is added and left standing overnight, to form [1-(ethene)2][BArF4]-Oct. Working under an atmosphere of ethylene (1 bar), the sample is then dissolved in a minimum volume of freshly degassed CH2Cl2 before quick filtration via cannula and layering with freshly degassed pentane. The sample is then stored at −78° C. and allowed to crystallise over at least a week. Single crystals, directly selected from the mother liquor, are suitable for X-ray diffraction analysis, however attempts to isolate the bulk sample resulted in the loss of crystallinity. Nevertheless solution NMR data are identical to [1-(ethene)2][BArF4] confirming the loss of long range order is not due to the loss of ethylene. Due to the limited amount of crystalline material obtained solid-state NMR spectroscopy was not undertaken. Isolated yield on the non-crystalline material: 77 mg (53.3 μmol, 79.2%).
1H solution NMR (CD2Cl2, 298 K, 400 MHz) δ: 7.72 (8H, s, o-BArF4), 7.56 (4H, s, p-BArF4), 4.43 (8H, v br, v1/2=94 Hz, ethylene), 2.0-1.0 ppm (multiple overlapping aliphatic resonances).
31P{1H} solution NMR (CD2Cl2, 298 K, 162 MHz) δ: 73.7 (v. br, v1/2≈500 Hz).
1H solution NMR (CD2Cl2, 193 K, 400 MHz) δ: 7.71 (8H, s, o-BArF4), 7.54 (4H, s, p-BArF4), 4.15 (8H, s, ethylene), 2.0-1.0 ppm (multiple overlapping aliphatic resonances).
31P{1H} solution NMR (CD2Cl2, 193 K, 162 MHz) δ: 73.6 (d, JRhP=145 Hz).
31P{1H} solid state NMR (for [1-(ethene)2][BArF4]-Oct; 162 MHz, 10 kHz spin rate) δ: 73.7 (br, v1/2≈410 Hz).
13C{1H} solid state NMR (for [1-(ethene)2][BArF4]-Oct; 101 MHz, 10 kHz spin rate) δ: 164.0 (BArF4), 134.7 (BArF4), 130.4 (BArF4), 125.3 (BArF4), 117.2 (BArF4), 82.23 (Ethylene) 15-40 (multiple overlapping aliphatic resonances).
Mass Spec found (calc.): 581.2189 (581.2907) note: there is considerable presence of [1-butadiene][BArF4] and decomposition product of formula m/z=[{(Cy2PCH2CH2PCy2)Rh}Cl2]2+-H2. There is no evidence for [1-butadiene][BArF4] in bulk samples so it is assumed to form via an in-situ ESI-MS process.
Elemental analysis found (calc.) (carried out with a sample of [1-(ethene)2][BArF4]-Hex): C 51.37% (51.51%), H 4.74% (4.63%). Satisfactory Elemental analysis for [1-(ethene)2][BArF4]-Oct has not been attained due to persistent contamination with excess norbornane.
Crystal structure: The transformation from [1-NBA][BArF4] to [1-(ethene)2][BArF4]-Oct is also a singlecrystal to single-crystal one, as shown by an X-ray structure determination at 150 K; and starting from [1-NBD][BArF4] this represents a rare example of a sequential reaction sequence for such processes.37 It is believed that the CF3 groups on the anions results in some plasticity in the solidstate lattice, which allows for the movement of the NBA,38 given that there are no clear channels in the crystal lattice. There is a space group change from to P21/n (Z=4) in [1-NBA][BArF4] to C2/c (Z=4) in [1-(ethene)2][BArF4]-Oct on substitution.
In the transformation from [1-(ethene)2][BArF4]-Oct to [1-(ethene)2][BArF4]Hex, the space group change is from monoclinic C2/c (Z=4) to hexagonal P6322 (Z=6).
It is noted that the structure of [1-(ethene)2][BArF4]-Oct has an elevated R-factor, as well as a low full θmax value. This is primarily due to a loss in high angle data—which is rationalised by the synthetic route (single-crystal to single-crystal to single-crystal!) putting strain on the lattice. For [1-(ethene)2][BArF4]-Hex no such loss of data is presented, however the CheckCif output contains one A alert due to the very large voids in the structure.
1.3—Synthesis and characterisation of [Rh(Cy2PCH2CH2PCy2)(η2-C3H6)][BArF4] ([1-propene][BArF4])
A crystalline sample of [1-C6H4F4][BArF4] (25 mg, 0.0166 mmol) was taken up in CD2Cl2 (0.5 ml) in a high pressure NMR tube. This was freeze-pump-thaw degassed (<1×10−2 mbar) three times before propylene gas (1 bar) was added. No discernible (by eye) colour change occured. 31P{1H} NMR spectroscopy indicated that very little conversion to [1-propene][BArF4] had occurred, with the bulk of the material remaining as the starting [1-C6H4F4][BArF4]. Any attempted work-up involving a vacuum results in either starting material or the complete decomposition of the species, to presumed solvent (C—H or C—Cl) activated products (indicated from mass spectroscopy showing the presence of chloride-bridged rhodium dimers). Furthermore leaving [1-propene][BArF4] in CH2Cl2 solution, at room temperature, resulted in similar decomposition over a period of approximately half an hour. To date it has not been possible to isolate [1-propene][BArF4] via solution methods.
To an orange sample of crystalline [1-NBA][BArF4] (25 m, 0.0168 mmol) in an evacuated (<1×10−2 mbar) J Young's flask (c. 50 ml) propylene gas (1 bar, 298 K) is added and left standing overnight. Little colour change is observed, but evidence of a colourless liquid/oil is sometimes observed on the sides of the flask (assumed to be liberated NBA)—it is this sample that was used for spectroscopic analysis. Under a propene atmosphere this compound appears stable for at least 72 hours at room temperature (shown by 31P{1H} solid state NMR). The long-term stability under an argon atmosphere has not been investigated. Attempts to recrystallize the material by dissolving in CH2Cl2 led to (presumably solvent induced) decomposition over the period of 30 mins (at room temperature). Dissolving the material in difluorobenzene resulted in the formation of [1-C6H4F2][BArF4]. In light of this attempts to recrystallize have been met with failure, and, because of the contamination of norbornane, it has not been possible to attain an acceptable elemental analysis. Yield: Quantitative (>95%) by 31P{1H} solution and solid state NMR (no other signals observed).
1H solution NMR (CD2Cl2, 500 MHz, 298 K) δ: 7.72 (8H, s o-BArF4), 7.56 (4H, s, p-BArF4), 5.07 (v br, propene), 2.10-1.00 (multiple overlapping aliphatic resonance, i.e. a forest).
31P{1H} solution NMR (CD2Cl2, 202 MHz, 298 K) δ: 95.2 (br d, JRhP=181 Hz).
1H solution NMR (CD2Cl2, 500 MHz, 193 K) δ: 7.71 (8H, s, o-BArF4), 7.54 (4H, s, p-BArF4), 4.84 (1H, br, propylene), 4.54 (1H, br, propene), 3.55 (1H, br, propene), 2.02-0.94 (multiple overlapping aliphatic resonances), -0.02 (3H, br, propene agostic CH3).
31P{1H} solution NMR (CD2Cl2, 202 MHz, 193 K) δ: 100.4 (br, JRhP=200 Hz), 89.9 (br, JRhP=161 Hz).
31P{1H} solid state NMR (162 MHz, 298 K, 10 kHz spin rate) δ: 95.6 (asym. br. s, v1/2=503 Hz).
31P{1H} solid state NMR (162 MHz, 158 K, 10 kHz spin rate) δ: 101.3 (br, v1/2=510 Hz), 90.4 (br, v1/2=463 Hz).
13C{1H} solid state NMR (101 MHz, 298 K, 10 kHz spin rate) δ: 164.0 (BArF4), 134.4 (BArF4), 130.4 (BArF4), 124.5 (BArF4), 118.4 (BArF4), 116.9 (BArF4), 93.7 (v. br, v1/2=582 Hz), 46-15 (multiple overlapping aliphatic resonances).
13C{1H} solid state NMR (101 MHz, 158 K, 10 kHz spin rate) δ: 163.7 (BArF4), 133.8 (BArF4), 130.1 (BArF4), 124.6 (BArF4), 118.4 (BArF4), 116.1 (BArF4), 94.2 (Propene C═C), 78.8 (Propene C═C), 46-15 (multiple aliphatic resonances), 6.5 (Propene agostic CH3).
H/D scrambling in [1-propylene-D3][BArF4]: In an effort to elucidate the precise mechanism of isomerisation of but-1-ene, model experiments were carried out using propylene-D3. [1-NBA][BArF4] (20 mg, 0.0135 mmol) was loaded into a high pressure NMR tube in an argon-filled glovebox. This was then sealed using a Teflon stop-cock, before transferring to a Schlenk-line and evacuated. The tube was refilled with propylene-D3 (1 bar). The head space was then monitored using gas-phase 2H{1H} NMR.
Mass Spec: Not stable under mass spectrometric conditions. Species observed (with appropriate isotopic distributions) at m/z=[{(Cy2PCH2CH2PCy2)Rh}2CH4Cl2]2+; RCy2PCH2CH2PCy2)Rh(C4H8)]+;[(Cy2PCH2CH2PCy2)Rh(C5H6)]+;[(Cy2PCH2CH2PCy2)Rh(C6H6)]+.
Crystal structure:
Similarly to [(1-ethene)2][BArF4]-Oct there is a somewhat elevated R-factor and a low emax value, again due to the loss of high angle data due to crystal quality degrading due to sequential single-crystal to single-crystal transformation.
A sample of [1-C6H4F2][BArF4] (20 mg, 0.0133 mmol) was taken up in CH2Cl2 before being freeze-pump-thawed degassed three times and but-1-ene (1 bar) was added. The yellow solution immediately turned orange, and continued to go deeper in colour. It was shown (via 31P{1H} solution NMR spectroscopy), conversion to [1-butadiene][BArF4] would occur over the period of one hour in solution.
In order to attain spectroscopic data for [1-butene][BArF4] but-1-ene gas (1 bar) is added to an orange sample of crystalline [1-NBA][BArF4] (20 mg) in a high pressure NMR tube at room temperature. The solid is allowed to stand for 5 minutes and then is exposed to a dynamic vacuum for 3 minutes (<1×10−2 mbar). The sample is then dissolved up in CD2Cl2 and NMR data immediately recorded. The dehydrogenation to produce the butadiene complex is considerably quicker in solution than in the solid state.
31P{1H} solution NMR (CD2Cl2, 202 MHz, 298 K) δ: 95.4 (br. d, JRhP=169 Hz).
31P{1H} solid state NMR (162 MHz, 298 K, 10 kHz spin rate) δ: 98.4 (br), 95.1 (br).
13C{1H} solid state NMR (101 MHz, 298 K, 10 kHz spin rate) δ: 164.3 (BArF4), 134.9 (BArF4), 130.3 (BArF4), 125.1 (BArF4), 120.6 (BArF4), 118.6 (BArF4), 116.7 (BArF4), 91.8 (br, butene), 42-15 (multiple overlapping aliphatic resonances), 6.3 (br, butene agostic).
Mass Spec found (calc.): Under mass spectral conditions the only identifiable signal is due to [1-butadiene][BArF4].
Identification of isomer of butene in [1-butene][BArF4]: In order to determine which isomer of butane (but-1-ene or but-2-ene) is present in the complex [1-butene][BArF4] in the solid state (and thus imply the resting state of the isomerisation catalysis) labelling studies were conducted (Scheme 3). [1-butene][BArF4] was made in-situ by addition of but-1-ene (1 bar) to [1-NBA][BArF4] (30 mg, 0.0202 mmol) in a high pressure NMR tube. This was allowed to stand for 5 minutes, before subjection to vacuum to remove excess but-1-ene gas (cycled three time), and then D2 gas was added (1 bar, to form butane-D2). The deuterated material was dissolved up in CH2Cl2 and 2H{1H} solution NMR was used to identify the locations of the deuterium atoms.
To an orange sample of crystalline [1-NBA][BArF4] (50 mg, 0.0333 mmol) in a J. Young's flask (c. 100 ml), but-1-ene gas (1 bar) is added and left standing for six hours. Over this time the sample goes a deep burgundy colour. Though crystallinity appears to be retained considerable data loss occurs (for single crystal X-ray diffraction), especially at high angle, and even getting absolute connectivity is not possible. 31P{1H} solution NMR on the dissolved sample showed the product to be formed quantitatively and to be chemically identical to that produced by solution route.
1H solution NMR (CD2Cl2, 500 MHz) : 7.72 (8H, s, o-BArF4), 7.56 (4H, s, p-BArF4), 5.47 (2H, br t, C2/C3, JHH≈9 Hz), 4.51 (2H, br d, C1/C4, JHH=6 Hz), 2.83 (2H, d, C1/C4, JHH=14 Hz).
31P{1H} solution NMR (CD2Cl2, 202 MHz) : 82.0 (d, JRhP=169 Hz).
31P{1H} solid state NMR δ: 81.0 (asym. br.).
13C{1H} solid state NMR δ: 164.3 (BArF4), 134.4 (BArF4), 130.3 (BArF4), 125.1 (BArF4), 118.6 (BArF4), 116.7 (BArF4), 103.5 (butadiene), 99.6 (butadiene), 87.8 (butadiene), 63.2 (butadiene), 42-15 (multiple overlapping aliphatic resonances).
Mass Spec found (calc.): 579.2733 (579.2750). Note considerable signal (with appropriate isotopic distribution) at m/z=[(Cy2PCH2CH2PCy2)Rh(C2H4)]+; [(Cy2PCH2CH2PCy2)Rh(C6H10)]+; [(Cy2PCH2CH2PCy2)Rh(C7H12)]+.
One Schlenk flask was charged with [Rh(cod)2][BArF4] (350 mg, 0.296 mmol) and dissolved in CH2Cl2 (5 mL). Then Cy2P(CH2)3PCy2 (1.5 mL, 0.2 M solution in C6H4F, 0.3 mmol) was added dropwise with vigorous stirring. The resulting light orange solution was allowed to stir for two hours at room temperature before the solvent was partially removed in vacuo (2 mL) and n-pentane (25 mL) was added. The resulting orange solid was filtered via cannula, washed with pentane (3×5 mL), and dried in vacuo to give [Rh(Cy2P(CH2)3PCy2)(η2:η2-C8H12)][BArF4] as an orange solid. Yield: 400 mg, 0.264 mmol, 89%.
1H solution NMR (400.1 MHz, CD2Cl2, 298K): δ 7.76 (br s, 8 H, BArF), 7.60 (s, 4H, BArF), 5.07 (br s, 4 H, C8H12), 2.38-2.22 (m, 12H, C8H12+phosphine), 1.96-1.79 (m, 22H, C8H12+phosphine), 1.51 (m, 4H, phosphine or C8H12), 1.42-1.10 (m, 20H, C8H12+phosphine). 11B{1H} solution NMR (128.4 MHz, CD2Cl2, 298K): δ-6.5 (s). 19F{1H} solution NMR (376.5 MHz, CD2Cl2, 298K): δ-62.9 (s). 31P{1H} solution NMR (162.0 MHz, CD2Cl2, 298K): δ 12.6 (d, JRhP2=139 Hz). Elemental analysis found (calculated) for C67H74P2F24BRh: C, 53.26 (53.37); H, 4.94 (4.91).
One Young's flask was charged with [Rh(Cy2P(CH2)3PCy2)(η2:η2-C8H12)][BArF4] (145 mg, 0.096 mmol) and dissolved in 1,2-F2C8H4 (3 mL). The orange solution was freeze-pump-thaw degassed three times before H2 gas (1 bar) was added. The reaction mixture was allowed to stir for one hour resulting in lighter orange solution, and then H2 and solvent were removed in vacuo. The resulting solid was washed with pentane (3×10 mL) and dissolved in CH2Cl2 (5 mL). Addition of an excess of norbornadiene (0.14 mL, 1.344 mmol) and stirring for one hour resulted in the darkening of the solution. The solvent was partially removed under vacuum (3.0 mL) and the resulting solution was filtered via cannula into a Young's crystallization tube. Crystals of [Rh(Cy2P(CH2)3PCy2)(η2:η2-C7H8)][BArF4] were obtained by layering the resulting solution with n-pentane. Yield: 96 mg, 0.063 mmol, 66%.
1H solution NMR (400.1 MHz, CD2Cl2, 298K): δ 7.72 (br s, 8H, BArF), 7.56 (s, 4H, BArF), 5.16 (br s, 4H, C7H8), 4.10 (s, 2 H, C7H8), 2.21 (overlapped br s, 2H each, C7H8), 1.96-1.73 (m, 26H, phosphine), 1.52 (m, 4H, phosphine), 1.40-1.17 (m, 20H, phosphine). 11B{1H} solution NMR (128.4 MHz, CD2Cl2, 298K): δ-6.5 (s). 19F{1H} solution NMR (376.5 MHz, CD2Cl2, 298K): δ-62.9 (s). 31P{1H} solution NMR (202.4 MHz, CD2Cl2, 298K): δ 15.7 (d, JRhP2=147 Hz). Elemental analysis found (calculated) for C66H70B1F24F2Rh1: C, 53.03 (52.92); H, 4.72 (4.55).
Addition of H2 gas (1 bar) to a crystalline samples of [Rh(Cy2P(CH2)3PCY2)(η2:η2-C7H8)][BArF4] led to the quantitative formation of [Rh(Cy2P(CH2)3PCy2)(η2:η2-C7H12)][BArF4] after 5 minutes. The crystalline sample goes opaque and dark upon hydrogenation.
Single crystal X-ray raw data were collected at 150 K using an Agilent SuperNova diffractometer (Cu Kα radiation, λ=1.54180 Å). Collected crystal lattice parameters: monoclinic (P2/n), a=19.07172(10), b=17.81061(10), c=19.83810(10), β=92.2275(5), V=6733.49(6), Z=4.
Addition of propene gas (1 bar) to a crystalline samples of [Rh(Cy2P(CH2)3PCY2)(η2:η2-C7H8)][BArF4] led to the quantitative formation of [Rh(Cy2P(CH2)3PCy2)(η2-Propene)][BArF4] after eight hours. The crystalline sample becomes light orange.
Single crystal X-ray raw data were collected at 100 K using a Rigaku 007 HF (High Flux) diffractometer (Cu Kα radiation, λ=1.54180 Å) equipped with a HyPix-600HE detector. Collected crystal lattice parameters: monoclinic (C2/c), a=19.2343(14), b=16.7377(11), c=20.0147(10), η=91.134(5), V=6442.2(7) Å3, Z=4.
Addition of H2 gas (1 bar) to a crystalline samples of [Rh(Cy2P(CH2)3PCY2)(η2:η2-C8H12)PArF4] led to the quantitative formation of RRh(Cy2P(CH2)3PCY2)(η2:η2-C8H14)][BArF4] after 30 mins. The crystalline sample goes opaque and dark orange upon hydrogenation.
Single crystal X-ray raw data were collected at 150 K using an Agilent SuperNova diffractometer (Cu Kα radiation, λ=1.54180 Å). Collected crystal lattice parameters: triclinic (P-1), a=13.0186(7), b=13.1664(7), c=20.1179(3), α=87.719(3), β=87.838(3), γ=86.484(4), V=3437.0(3) Å3, Z=2.
One Schlenk flask was charged with [Rh(cod)2][BArF4] (270 mg, 0.228 mmol) and another filled with Cy2P(CH2)4PCy (103 mg, 0.228 mmol). Both solids were dissolved in CH2Cl2 (3 mL each) and the phosphine was added dropwise to [Rh(cod)2][BArF4] via cannula with vigorous stirring. The resulting light orange solution was allowed to stir for two hours at room temperature before the solvent was partially removed in vacuo (2 mL) and n-pentane (25 mL) was added. The resulting orange solid was filtered via cannula, washed with pentane (3×5 mL), and dried in vacuo to give [Rh(Cy2P(CH2)4PCy2)(η2:η2-C8H12)][BArF4] as an orange solid. Yield: 300 mg, 0.197 mmol, 86%.
1H solution NMR (400.1 MHz, CD2Cl2, 298K): δ 7.72 (br s, 8H, BArF), 7.57 (s, 4H, BArF), 5.02 (br s, 4 H, C8H12), 2.37-2.18 (m, 12H, C8H12+phosphine), 1.86-1.74 (m, 24 H, C8H12+phosphine), 1.56 (m, 4H, phosphine or C8H12), 1.37-1.28 (m, 20H, C8H12+phosphine). 11B{1H} solution NMR (128.4 MHz, CD2Cl2, 298K): δ-6.5 (s). 19F{1H} solution NMR (376.5 MHz, CD2Cl2, 298K): δ-62.9 (s). 31P{1H} solution NMR (162.0 MHz, CD2Cl2, 298K): δ 12.5 (d, JRhP2=140 Hz). Elemental analysis found (calculated) for C68H76B1F24P2Rh1: C, 53.56 (53.49); H, 4.02 (4.91).
One Young's flask was charged with Rh(Cy2P(CH2)4PCy2)(η2:η2-C8H12)][BArF4] (220 mg, 0.144 mmol) and dissolved in 1,2-F2C6H4 (3 mL). The orange solution was freeze-pump-thaw degassed three times before H2 gas (1 bar) was added. The reaction mixture was allowed to stir for one hour before H2 and solvent were removed in vacuo. The remaining solid was washed with pentane (3×10 mL) and then dissolved in CH2Cl2 (3 mL). Addition of an excess of norbornadiene (0.22 mL, 2.166 mmol) and stirring for one hour resulted in the darkening of the solution. The solvent was partially removed under vacuum (2.0 mL) and the resulting solution was filtered via cannula into a Young's crystallization tube. Crystals of [Rh(Cy2P(CH2)4PCy2)(η2:η2-C7H12)][BArF4} were obtained by layering the resulting solution with n-pentane. Yield: 168 mg, 0.111 mmol, 77%.
1H solution NMR (400.1 MHz, CD2Cl2, 298K): δ 7.72 (m, 8 H, BArF), 7.57 (s, 4H, BArF), 4.91 (overlapped dt, 4H, JHH=2.5, 1.9 Hz, C7H8), 4.04 (br s, 2 H, C7H8), 2.15 (br s, 4H, C7H8), 1.94-1.68 (m, 30H, phosphine), 1.43-1.21 (m, 22H, phosphine). “B{1H} solution NMR (128.4 MHz, CD2Cl2, 298K): δ-6.6 (s). 19F{1H} solution NMR (376.5 MHz, CD2Cl2, 298K): 8 -62.9 (s). 31P{1H} solution NMR (162.0 MHz, CD2Cl2, 298K): δ 26.8 (d, JRhP2=152 Hz). Elemental analysis found (calculated) for C67H72P2F24BRh: C, 53.33 (53.26); H, 4.81 (4.60).
Addition of H2 gas (1 bar) to a crystalline samples of [Rh(Cy2P(CH2)4PCY2)(η2:η2-C7H8)][BArF4] led to the quantitative formation of [Rh(Cy2P(CH2)4PCy2)(η2:η2-C7H12)][BArF4] after 5 minutes. The crystalline sample goes opaque and dark upon hydrogenation.
Single crystal X-ray raw data were collected at 150 K using an Agilent SuperNova diffractometer (Cu Kα radiation, λ=1.54180 Å). Collected crystal lattice parameters: monoclinic (P2/n), a=19.00390(10), b=18.02740(10), c=20.06620(10), β=92.2230(10), V=6869.33(6), Z=4.
Addition of propene gas (1 bar) to a crystalline samples of [Rh(Cy2P(CH2)3PCy2)(η2:η2-C7H8)][BArF4] led to the quantitative formation of [Rh(Cy2P(CH2)4PCy2)(η2-Propene)][BArF4] after eight hours. The crystalline sample becomes light orange.
Single crystal X-ray raw data were collected at 100 K using a Rigaku 007 HF (High Flux) diffractometer (Cu Kα radiation, λ=1.54180 Å) equipped with a HyPix-600HE detector. Collected crystal lattice parameters: monoclinic (C2/c), a=18.773(5), b=16.951(2), c=19.809(3), β=90.109(15), V=6303(2) Å3, Z=4.
One Schlenk flask was charged with [Cy2PLi.(THF)]—(1 g, 3.62 mmol) and suspended in dry 1,4-dioxane (15 mL) at room temperature. Then, 1,5-dibromopentane (0.24 mL, 1.76 mmol) was added dropwise via syringe promptly producing a colourless solution. The solution was stirred at room temperature for two hours yielding a white suspension. The resulting suspension was filtered via cannula and 1,4-dioxane was removed in vacuo to give a colourless solid. This solid was dissolved in dry ethanol (15 mL) upon warming up. Cy2P(CH2)5PCy2 was obtained as a colorless crystalline solid by storing the resulting solution at 4° C. for 24 h. Yield: 620 mg, 1.33 mmol, 76%.
1H solution NMR (400.1 MHz, C6D6, 298K): δ 1.89-1.50 (m, 30H), 1.42 (m, 4H, phosphine), 1.32-1.15 (m, 20H). 31P{1H} solution NMR (162.0 MHz, C6D6, 298K): δ-5.8 (d, JRhP2=139 Hz). 13C{1H} solution NMR (100.6 MHz, C6D6, 298K): 8 34.0 (d, JCP=15 Hz, CH), 30.9 (d, JCP=15 Hz), 29.5 (d, JCP=9 Hz), 28.8 (d, JCp=21 Hz), 27.76 (d, JCP=17 Hz), 27.74 (br s), 27.0 (s), 21.9 (d, JCP=19 Hz).
One Schlenk flask was charged with [Rh(cod)2][BArF4] (500 mg, 0.423 mmol) and another filled with Cy2P(CH2)5PCy (197 mg, 0.423 mmol). Both solids were dissolved in CH2Cl2 (5 mL each) and the phosphine was added dropwise to [Rh(cod)2][BArF4] via cannula with vigorous stirring. The resulting light orange solution was allowed to stir for two hours at room temperature before the solvent was partially removed in vacuo (4 mL) and n-pentane (25 mL) was added. The resulting orange solid was filtered via cannula, washed with pentane (3×10 mL), and dried in vacuo to give [Rh(Cy2P(CH2)5PCy2)(η2:η2-C8H12)][BArF4] as an orange solid.
1H solution NMR (400.1 MHz, CD2Cl2, 298K): δ 7.72 (br s, 8H, BArF), 7.56 (s, 4H, BArF), 4.90 (br s, 4H, C8H12), 2.37-1.52 (several m, 42H, C8H12+phosphine), 1.53-1.26 (m, 20H, C8H12+phosphine). “B{1H} solution NMR (128.4 MHz, CD2Cl2, 298K): δ-6.5 (s). 19F{1H} solution NMR (376.5 MHz, CD2Cl2, 298K): δ-62.9 (s). 31P{1H} solution NMR (162.0 MHz, CD2Cl2, 298K): δ 8.3 (d, JRhP2=138 Hz).
One Young's flask was charged with [Rh(Cy2P(CH2)8PCy2)(η2:η2-C8H12)][BArF4] (160 mg, 0.104 mmol) and dissolved in 1,2-F2C8H4 (3 mL). The orange solution was freeze-pump-thaw degassed three times before H2 gas (1 bar) was added. The reaction mixture was allowed to stir vigorously for 5 mins and it was immediately freeze-pump-thaw degassed three times to remove H2. n-Pentane (25 mL) was then added to give a pale yellow suspension. The resulting solid was filtered via cannula, washed with pentane (3×10 mL), dried in vacuo and then dissolved in CH2Cl2 (3 mL). Addition of an excess of norbornadiene (0.15 mL, 1.47 mmol) and stirring for one hour gave a dark red solution. The solvent was partially removed under vacuum (1.5 mL) and the solution was filtered via cannula into a Young's crystallization tube. Crystals of [Rh(Cy2P(CH2)5PCy2)(η2:η2-C7H8)][BArF4] were obtained by layering the resulting solution with n-pentane. Yield: 140 mg, 0.091 mmol, 88%.
1H solution NMR (400.1 MHz, CD2Cl2, 298K): δ 7.71 (br s, 8H, BArF), 7.56 (s, 4H, BArF), 4.69 (br m, 4H, C7H8), 3.97 (br s, 2H, C7H8), 2.22 (m, 4H, C7H8), 1.91-1.68 (m, 34H, phosphine), 1.43-1.21 (m, 20H, phosphine). 11B{1H} solution NMR (128.4 MHz, CD2Cl2, 298K): δ-6.6 (s). 19F{1H} solution NMR (376.5 MHz, CD2Cl2, 298K): δ-62.9 (s). 31P{1H} solution NMR (162.0 MHz, CD2Cl2, 298K): δ 18.7 (d, JRhP2=150 Hz).
Addition of H2 gas (1 bar) to a crystalline samples of [Rh(Cy2P(CH2)3PCy2)(η2:η2-C7H8)][BArF4] led to the quantitative formation of a compound of formulae “[Rh(Cy2P(CH2)5PCY2)(η2:η2-C7H12)][BArF4]” after 5 minutes. The crystalline sample turned yellow upon hydrogenation.
Single crystal X-ray raw data were collected at 100 K using an Agilent SuperNova diffractometer (Cu Kα radiation, λ=1.54180 Å). Collected crystal lattice parameters: monoclinic (/2/a), a=20.6165(3), b=17.74689(19), c=77.1292(6), β=94.5127(9), V=28132.4(5), Z=20.
A stirred slurry of Na[BArCl4] (168 mg, 0.27 mmol) and NBD (0.25 mL) in CH2Cl2 (20 mL) was treated with a yellow solution of [Rh(Cy2PCH2CH2PCy2)Cl]2 (153 mg, 0.136 mmol) in CH2Cl2 (10 mL). The resultant red mixture was stirred at ambient temperature for 4 h and then filtered. The filtrate was concentrated under vacuum (ca. 2 mL) and layered with pentane. Dark orange crystals suitable for an x-ray diffraction study were obtained. Yield: 273 mg (84%).
1H NMR (CD2Cl2, 400 MHz, 298 K): δ 7.04 (m, 8H, ortho-ArH), 7.01 (t, 4H, para-ArH), 5.53 (br s, 4H, alkene CH), 4.17 (br s, 2H, bridgehead CH), 2.00-1.98 (br d, 4H, overlapping aliphatic CH), 1.93-1.65 (m, 26H, overlapping aliphatic CH), 1.36-1.19 (m, overlapping 16H, aliphatic CH), 1.14-1.04 (m, 4H, overlapping aliphatic CH). 31P{1H} NMR (CD2Cl2, 162 MHz): δ 69.9 (d, JRhP 154Hz). 11B{1H} NMR (CD2Cl2, 128 MHz, 298 K): δ-6.9 (s). 31P{1H} SSNMR (162 MHz, 10 kHz spin rate, 294 K): δ 64.7 (d, JRhP 145 Hz), 63.0 (d, JRhP 147 Hz). 13C{1H} SSNMR (101 MHz, 10 kHz spin rate, 294 K):δ 165.3 (br, [BArCl4]−), 134.7 ([BArCl4]−), 131.1 (br, [BArCL4]−), 122.5 ([BArCl4]−), 88.4 (C═C), 87.4 (C═C), 80.3 (C═C), 79.4 (C═C), 69.8 (bridge C), 55.1 (2C, bridgehead C), 34.2-18.9 (multiple aliphatic resonances). 1H projection from 1H/13C Frequency Switched Lee-Goldburg HETCOR SSNMR: δ 7.02 (br), 2.18 (br). ESI-MS found (calc.): m/z 617.29 (617.29). Elemental analysis found (calc. for C57H68BCl8P2Rh): C 56.31 (56.47), H 5.70 (5.65).
A stirred slurry of Na[BArF4] (91 mg, 0.19 mmol) and NBD (0.25 mL) in CH2Cl2 (20 mL) was treated with a yellow solution of [Rh(Cy2PCH2CH2PCy2)Cl]2 (96 mg, 0.086 mmol) in CH2Cl2 (10 mL). The resultant red mixture was stirred at ambient temperature for 4 h and then filtered. The filtrate was concentrated under vacuum (ca. 1 mL) and layered with pentane. Dark orange crystals suitable for an x-ray diffraction study were obtained. Yield: 154 mg (83%).
1H NMR (CD2Cl2, 400 MHz, 298 K): δ 6.74 (m, 8H, ortho-ArH), 6.42 (br t, 4H para-ArH), 5.53 (br s, 4H, alkene CH), 4.17 (br s, 2H, bridgehead CH), 2.01-1.98 (br d, 4H, overlapping aliphatic CH), 1.93-1.67 (m, 26H, overlapping aliphatic CH), 1.37-1.19 (m, 16H, overlapping aliphatic CH), 1.14-1.04 (m, 4H, overlapping aliphatic CH). 31 P{1H} NMR (CD2Cl2, 162 MHz, 298 K): 6 69.8 (d, JRhP 154 Hz). 116{1H} NMR (CD2Cl2, 128 MHz, 298 K): δ-6.6 (s). 19F{1H} NMR (CD2Cl2, 376 MHz, 298 K): δ-115.2 (s). 31 P{1H} SSNMR (162 MHz, 10 kHz spin rate, 294 K): δ 70.9 (br s). 13C{1H} SSNMR (101 MHz, 10 kHz spin rate, 294 K): δ 162.5 (m, [BArF4]−), 116.8 ([BArF4]−), 114.3 ([BArF4]−), 97.7 ([BArF4]−), 89.3 (C═C), 79.6 (C=C), 71.4 (bridge C), 54.4 (bridgehead C), 34.5-20.7 (multiple aliphatic resonances). 1H projection from 1H/13C Frequency Switched Lee-Goldburg HETCOR SSNMR: δ 6.42 (br), 2.65 (br). ESI-MS found (calc.): m/z 617.29 (617.29). Elemental analysis found (calc. for C57H68BF8P2Rh): C 3.26 (63.34), H 6.42 (6.34).
A stirred slurry of Na[BArH4] (55 mg, 0.16 mmol) and NBD (0.25 mL) in CH2Cl2 (20 mL) was treated with a yellow solution of [Rh(Cy2PCH2CH2PCy2)Cl]2 (90 mg, 0.080 mmol) in CH2Cl2 (10 mL). The resultant red mixture was stirred at ambient temperature for 4 h and then filtered. The filtrate was concentrated under vacuum (ca. 1 mL) and layered with pentane. Dark orange crystals suitable for an x-ray diffraction study were obtained. Yield: 117 mg (78%).
1H NMR (CD2Cl2, 400 MHz, 298 K): δ 7.32 (br m, 8H, ortho-ArH), 7.04 (br t, JHH 7.5 Hz, 8H, meta-ArH), 6.89 (br t, JHH 7.5 Hz, 4H, para-ArH), 5.52 (br s, 4H, alkene CH), 4.16 (s, 2H, bridgehead CH), 1.99 (br d, JHH 12.3 Hz, 4H, overlapping aliphatic CH), 1.92-1.61 (m, 26H, overlapping aliphatic CH), 1.38-1.20 (m, 16H, overlapping aliphatic CH), 1.14-1.01 (m, 4H, overlapping aliphatic CH). 31P{1H} NMR (CD2Cl2, 162 MHz, 298 K): δ 69.8 (d, JRhP 154 Hz). 11B{1H} NMR (CD2Cl2, 128 MHz, 298 K): δ-6.6 (s). 31 P{1H} SSNMR (162 MHz, 10 kHz spin rate, 293 K): δ 75.8 (d, JRhP 134 Hz), 64.8 (d, JRhP 132 Hz). 13C{1H} SSNMR (101 MHz, 10 kHz spin rate, 293 K): δ 165.2-158.5 (m, [BArH4]−), 136.2-135.1 (m, [BArE14]−), 125.6-120.7 (m, [BArH4]), 89.3 (C═C), 85.4 (C═C), 83.8 (C═C), 81.8 (C═C), 70.6 (bridge C), 54.5 (2C, bridgehead C), 35.8-15.8 (multiple aliphatic resonances). 1H projection from 1H/13C Frequency Switched Lee-Goldburg HETCOR SSNMR: δ 6.98 (br), 2.00 (br). ESI-MS found (calc.): m/z 617.29 (617.29). Elemental analysis found (calc. for C57H76BP2Rh): C 73.13 (73.07), H 8.08 (8.18).
A solution of [Rh(NBD)2][Al{OC(CF3)3}4] (123 mg, 0.10 mmol) in CH2Cl2 (40 mL) was treated dropwise with a solution of dcpe (42 mg, 0.99 mmol) in CH2Cl2 (20 mL) at −60° C. Upon complete addition the color of the reaction solution changed from burgundy to orange. After 2 h, the solution was allowed to warm to ambient temperature. The solvent was then removed under vacuum and the resultant red residue was washed with pentane (3×10 mL). Extraction into CH2Cl2 (2 mL) followed by layering with pentane afforded large red crystals suitable for an x-ray diffraction study. Yield: 127 mg (80%).
1H NMR (CD2Cl2, 400 MHz, 298 K): δ 5.54 (br s, 4H, alkene CH), 4.20 (br s, 2H, bridgehead CH), 2.02-1.98 (br d, 4H, overlapping aliphatic CH), 1.93-1.61 (m, 26H, overlapping aliphatic CH), 1.36-1.21 (m, overlapping 16H, aliphatic CH), 1.14-1.04 (m, 4H, overlapping aliphatic CH). 31P{1H} NMR (CD2Cl2, 202 MHz): δ 69.8 (d, JRhP 154Hz). 27Al NMR (CD2Cl2, 104 MHz, 298 K): δ 34.6 (s). 31P{1H} SSNMR (162 MHz, 10 kHz spin rate, 294 K): δ 70.2 (d, JRhP 155 Hz), 69.0 (d, JRhP 156 Hz). 13C{1H} SSNMR (101 MHz, 10 kHz spin rate, 294 δ K):121.6 (br q, JCF 280 Hz, CF3), 94.1 (C═C, 2C), 84.7 (C═C), 82.5 (d, C═C), 79.5 (AIDC), 72.0 (bridge C), 56.5 (bridgehead C), 56.0 (bridgehead C), 38.7-22.3 (multiple aliphatic resonances). 27Al SSNMR (104 MHz, 15 kHz spin rate, 294 K): δ 33.7. 1H projection from 1H/13C Frequency Switched Lee-Goldburg HETCOR SSNMR: δ 6.00 (br), 4.51 (br), 1.97 (br). ESI-MS found (calc.): m/z 617.29 (617.29). Elemental analysis found (calc. for C43H56AlF36O4P2Rh): C 37.08 (37.14), H 3.47 (3.56).
Hydrogenation (1 atm) of a crystalline sample of [Rh(Cy2PCH2CH2PCy2)(NBD)][BArCl4] led to the formation of [Rh(Cy2PCH2CH2PCy2)(NBA)][BArCl4] in 1 h.
31P{1H} SSNMR (162 MHz, 10 kHz spin rate, 158 K): δ 101.5 (br), 94.7 (br). 13C{1H} SSNMR (101 MHz, 10 kHz spin rate, 158 K):δ 163.7 (br, [BArCl4]−), 131.5 (br, [BArCl4]−), 121.9 ([BArCl4]−), 37.0-14.6 (multiple aliphatic resonances). 1H projection from 1H/13C Frequency Switched Lee-Goldburg HETCOR SSNMR: δ 7.05 (br), 2.29 (br), −1.76 (br).
Hydrogenation (1 atm) of a crystalline sample of [Rh(Cy2PCH2CH2PCy2)(NBD)][BArF4] led to the formation of [Rh(Cy2PCH2CH2PCy2)(NBA)][BArF4] in 3 h.
31P{1H} SSNMR (162 MHz, 10 kHz spin rate, 158 K): δ 103.6 (br). 13C{1H} SSNMR (101 MHz, 10 kHz spin rate, 158 K):δ 165.5-159.7 (br m, [BArF4]−), 116.2 ([BArF4]−), 114.1 ([BArF4]−), 97.4 ([BArF4]−), 35.1-20.2 (multiple aliphatic resonances). 1H projection from 1H/13C Frequency Switched Lee-Goldburg HETCOR SSNMR: δ 6.45 (br), 2.64 (br), −1.62 (br).
Hydrogenation (1 atm) of a crystalline sample of [Rh(Cy2PCH2CH2PCy2)(NBD)] [Al{OC(CF3)3}4] led to the formation of [Rh(Cy2PCH2CH2PCy2)(H)2][Al{0C(CF3)3}4] in 1 h.
31P{1H} SSNMR (162 MHz, 10 kHz spin rate, 294 K): δ 99.5 (br). 13C{1H} SSNMR (101 MHz, 10 kHz spin rate, 294 K):δ 121.6 (br q, JCF 280 Hz, CF3), 79.3 (AIDC), 38.2-19.9 (multiple aliphatic resonances). 27Al SSNMR (104 MHz, 15 kHz spin rate, 294 K): δ 32.7. 1H projection from 1H/13C Frequency Switched Lee-Goldburg HETCOR SSNMR: δ 2.00 (br). Elemental analysis found (calc. for C42H50AlF36O4P2Rh): C 33.73 (33.75), H 3.19 (3.37).
The complexes [1-NBA][BArF4], [1-(ethene)2][BArF4]-Oct, [1-(ethene)2][BArF4]-Hex have been screened (but conditions not optimised) in the isomerization of 1-butene to 2-butene in solid/gas catalysis, acting SMOM-cat. This was performed on a small, but convenient, scale by taking a thick-walled NMR tube of volume ca. 1.9 cm3 fitted with Teflon stopcock that allows for the addition of gases, adding a crystalline sample of catalyst (˜3 mg, ˜2 gmoles), brief evacuation, refilling with 1-butene gas (15 psi, ˜79 gmoles78) and analysis by gas-phase 1H NMR spectroscopy. This loading, assuming all sites in the crystalline material have the same activity, gives TON(bulk) of ˜42 for 100% conversion. This represents a minimum TON, as if only the most accessible sites, or those nearest to the surface, were kinetically competent then the actual number of active sites would be lower. To probe the influence of surface area for [1-NBA][BArF4], large (edge length ca. 1-2 mm) crystals and finely crushed samples were prepared for which the surface area would be significantly greater. For both polymorphs of [1-(ethene)2][BArF4] crushed samples were used as large crystals could not be grown (
[1-NBA][BArF4] (big crystals) was used to catalyse the conversion of but-1-ene to but-2-ene. Conditions used: 2.5 mg catalyst loading, 15 psi but-1-ene, NMR tube volume 1.9 ml. The results are presented in Table 1.
[1NBA][BArF4] (crushed crystals) was used to catalyse the conversion of but-1-ene to but-2-ene. Conditions used: 2.0 mg catalyst loading, 15 psi but-1-ene, NMR tube volume 1.9 ml. The results are presented in Table 2.
[1-(ethene)2][BArF4]-Oct was used to catalyse the conversion of but-1-ene to but-2-ene. Conditions used: 2.6 mg catalyst loading, 15 psi but-1-ene, NMR tube volume 1.8 ml. The results are presented in Table 3.
[1-(ethene)2][BArF4]-Hex was used to catalyse the conversion of but-1-ene to but-2-ene. Conditions used: 6.0 mg catalyst loading, 15 psi but-1-ene, NMR tube volume 1.9 ml. The results are presented in Table 4.
The recyclability of [1-NBA][BArF4] (big crystals) in the conversion of but-1-ene to but-2-ene was assessed. Conditions used: 2.6 mg catalyst loading, 15 psi but-1-ene, 1.8 ml NMR tube volume. The results are presented in Table 5.
200
3.333
87
258
The recyclability of [1-NBA][BArF4] (crushed crystals) in the conversion of but-1-ene to but-2-ene was assessed. Conditions used: 3.4 mg catalyst loading, 15 psi but-1-ene, 1.8 ml NMR tube. The results are presented in Table 6.
The recyclability of [1-(ethene)2][BArF4]-Oct (crushed crystals) in the conversion of but-1-ene to but-2-ene was assessed. Conditions used: 2.6 mg cat. Loading, 15 psi but-1-ene, 1.8 ml NMR tube. The results are presented in Table 7.
The recyclability of [1(ethene)2][BArF4]-Hex (crushed crystals) in the conversion of but-1-ene to but-2-ene was assessed. Conditions used: 6.0 mg cat. Loading, 15 psi but-1-ene, 1.9 ml NMR tube. The results are presented in Table 7.
The four catalyst systems ([1-NBA][BArF4] (big crystals), [1-NBA][BArF4] (crushed crystals), [1-(ethene)2][BArF4]-Oct (crushed crystals) and [1-(ethene)2][BArF4]-Hex (crushed crystals)) can all be recycled, and
In contrast to the exemplary catalysts, comparator catalysts containing isobutyl ligands instead of cyclohexyl ligands ([(Bu2PCH2CH2PiBu2)Rh(η2:η2-C7H12)][BArF4] [iBu-NBA] and [(lPu2PCH2CH2PBu2)Rh(η2-C2H4)2HBArF4] [iBu-(ethene)2]) demonstrated no recyclability.
Samples of [1-NBA][BArF4] (big crystals) and [1-NBA][BArF4] (crushed crystals) were exposed to CO (2 bar) for 150 seconds. Solution 31P{1H} NMR showed the sample had gone to 70% completion. [(Cy2PCH2CH2PCy2)Rh(CO)2][BArF4] is inactive in the catalytic isomerisation of butane. The surface of the crystals (both big and crushed) would react faster than the bulk, effectively turning off the surface for catalysis—the intention being investigating whether this is a surface process or bulk process. However with [1-NBA][BArF4] (big crystals) it was noted that significant fracturing of the crystals occurred during the exposure to CO (and presumably the same would be happening on [1-NBA][BArF4] (crushed crystals), but not be observable by the naked eye).
Similar studies were carried out with [1-(ethene)2][BArF4]Oct and [1-(ethene)2][BArF4]-Hex, however due to the small amount of sample of both available quantification of the extent of passivation by 31 P{1H} NMR was not possible. The same conditions were used (150 seconds of CO at 2 bar).
CO-passivated [1-NBA][BArF4] (big crystals) was used to catalyse the conversion of but-1-ene to but-2-ene. Conditions used: 2.8 mg cat. Loading, 15 psi but-1-ene, 1.9 ml NMR tube volume. The results are presented in Table 9.
CO-passivated [1-NBA][BArF4] (crushed crystals) was used to catalyse the conversion of but-1-ene to but-2-ene. Conditions used: 2.6 mg cat. Loading, 15 psi but-1-ene, 1.8 ml NMR tube volume. The results are presented in Table 10.
It has been shown that addition of CO(g) to crystalline samples of [Rh(Bu2PCH2CH2PBu2)(η2,η2-C4H6)][BArF4] is slow enough (days) to form a catalytically inactive, passivated, layer of [Rh(Bu2PCH2CH2PBu2)(CO)2][BArF4] in the resulting crystalline material.42 This allows for the activity of surface sites to be probed in catalysis, which were suggested to be considerably more active compared to the bulk. This approach was inspired by the work of Brookhart on single-crystal solid/gas catalysis using [PCPiPr=κ3-C6H3-2,6-(OP(C6H2-2,4,6-(CF3)3)2]43 For the complexes reported here reaction with CO is much faster, i.e. large crystals of [1-NBA][BArF4] react in ˜2 minutes to form [(Cy2PCH2CH2PCy2)Rh(CO)2][BArF4] in 70% conversion. At the same time considerable cracking of the crystals also occurred, that likely exposes the interior of the crystals.” This means that passivation of just the surface sites is problematic and has therefore not been pursued further with these samples. However, that [1-NBA][BArF4]-large shows a significantly lower TOF (based on the bulk) compared to more finely—divided [1-NBA][BArF4]-crushed and [1-(ethene)2][BArF4]-Oct suggests that surface effects are import here, and the most active catalyst sites sit at, or near, the surface. This hypothesis is further strengthened by the larger TOF for porous [1-(ethene)2][BArF4]-Hex in which a significant proportion, if not all, of the metal sites are potentially active; pointing as they do into the large cylindrical pores of the single-crystal.
In summary, it is believed that catalysts such as [1-(ethene)2][BArF4]-Hex are the first well-defined molecular systems that operate at 298 K under, industrially appealing, solid/gas conditions. In addition, they offer fine control of the spatial environment in the solid-state (i.e. show structure/activity relationships), show TOF(min) that are competitive with the fast homogenous systems, and, moreover are recyclable.
The ability of compounds [Rh(Cy2P(CH2)3PCy2)(η2:η2-C7H12)][BArF4], [Rh(Cy2P(CH2)4PCy2)(η2:η2-C7H12)][BArF4], [Rh(Cy2P(CH2)5PCy2)(η2:η2-C7H12)][BArF4], [Rh(Cy2P(CH2)3PCy2)(η2-Propene)][BArF4], [Rh(Cy2P(CH2)2PCy2)(η2:η2-C7H12)][BArH4], [Rh(Cy2P(CH2)2PCy2)(η2:η2-C7H12)][BAr(F)4], [Rh(Cy2P(CH2)2PCy2)(η2:η2-C7H12)][BArH4] (comparator, prepared in situ) and [Rh(Cy2P(CH2)2PCy2)(H)2][Al{OC(CF3)3}4] to catalyse the isomerisation of 1-butene to 2-butene was assessed. The results are presented in Tables 11-18 below:
The data presented in Tables 11-18 show that compounds [Rh(Cy2P(CH2)3PCy2)(η2:η2-C7H12)][BArF4], [Rh(Cy2P(CH2)4PCy2)(η2:η2-C7H12)][BArF4], [Rh(Cy2P(CH2)5PCy2)(η2:η2-C7H12)][BArF4], [Rh(Cy2P(CH2)3PCy2)(η2-propene)][BArF4], [Rh(Cy2P(CH2)2PCy2)(η2:η2- C7H12)][BArCl4], [Rh(Cy2P(CH2)2PCy2)(η2:η2-C7H12)][BAr(F)4] and [Rh(Cy2P(CH2)2PCy2)(H)2][Al{OC(CF3)3}4] are effective catalysts in the conversion of 1-butene to 2-butene.
The ability of compounds [Rh(Cy2P(CH2)2PCy2)(η2:η2-C7H12)][BArF4], [Rh(Cy2P(CH2)5PCy2)(η2:η2-C7H12)][BArF4], [Rh(Cy2P(CH2)4PCy2)(η2:η2-C7H12)][BArF4] and [Rh(Cy2P(CH2)3PCy2)(η2:η2-C7H12)][BArF4] to catalyse the isomerisation of 1-butene to 2-butene was assessed. The results are presented in
The ability of compounds [Rh(Cy2P(CH2)2PCy2)(η2:η2-C7H12)][BArF4], [Rh(Cy2P(CH2)2PCy2)(H)2][Al{OC(CF3)3}4], [Rh(Cy2P(CH2)2PCy2)(η2:η2-C7H12)][BArF4], [Rh(Cy2P(CH2)2PCy2)(η2:η2-C7H12)][BAr(F)4] and [Rh(Cy2P(CH2)2PCy2)(η2:η2-C7H12)][BArF4] (comparator, prepared in situ) to catalyse the isomerisation of 1-butene to 2-butene was assessed. The results are presented in
Scale-up experiments were performed by loading crystalline samples of each catalyst (1.0-2.5 mg, ca. 0.7-1.7 μmol) into a high-pressure reactor of volume 61 mL fitted with Teflon stopcocks that allows for the addition of 1-butene gas (15-24 psi, 86-138 μmol), see
These catalytic loadings gave TON(90%) of ca. 6000 for catalysis.
The ability for [1-NBA][BArF4]-crushed and [1-(ethene)2][BArF4]-Hex to mediate the gas/solid transfer dehydrogenation of butane to butenes has been briefly explored (Scheme 3), as monitored by gas-phase NMR spectroscopy. A typical experiment was as follows a high pressure NMR tube (sealed with a Teflon stopcock) was loaded with 10 mg (0.00673 mmol) of [1-NBA][BArF4] in an argon-filled glove box. This was then taken out of the glove box, and evacuated on a Schlenk line (<1×10−2 mbar). To this butane gas was added (1 bar, 0.0762 mmol)) and the stopcock sealed. The gas feed was changed to ethene and set to the appropriate pressure (Table 19). The glass T-piece and connecting tubing was evacuated and refilled three times (with ethene), before the stopcock was opened. The loaded tubes were left to stand, and the reaction monitored by gas phase 1H NMR of the head space.
Periodic monitoring of the head space in the NMR tube showed that slow transfer dehydrogenation was occurring to form 2-butene, presumably by slow dehydrogenation to form 1-butene (not observed) and rapid isomerization. For [1-NBA][BArF4]-crushed, after 168 hrs at 298 K there was a 33% conversion, which equates to ˜4 turnovers. The catalysis was also shown to operate at 80° C. with an excess of ethene (2:1), under which conditions 68% conversion of butane to butenes is observed (TON=4). Although these turnover numbers are smaller those reported for the best solid-phase molecular catalyst Ir(PCPiPr)(C2H4) in the pentane/propene system at 240° C. (e.g. TON greater than 1000), the observation of any catalytic activity at 298 K for this challenging reaction is encouraging. It is believed that this is the first time solid/gas transfer dehydrogenation has been reported using a well-defined molecular catalyst at room temperature and low pressures.
The ability of [1-NBA][BArF4]-crushed to effect the dimerization of ethene has been briefly assessed.
While specific embodiments of the invention have been described herein for the purpose of reference and illustration, various modifications will be apparent to a person skilled in the art without departing from the scope of the invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1619935.8 | Nov 2016 | GB | national |
| 1714399.1 | Sep 2017 | GB | national |
This application is a U.S. national stage filing, under 35 U.S.C. § 371(c), of International Application No. PCT/GB2017/053514, filed on Nov. 22, 2017, which claims priority to United Kingdom Application No. 1714399.1, filed on Sep. 7, 2017; and United Kingdom Application No. 1619935.8, filed on Nov. 24, 2016. The entire contents of each of the aforementioned applications are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2017/053514 | 11/22/2017 | WO | 00 |
