Patent Application
20070191638
This invention provides processes for the synthesis of N,N′-substituted 1,3-diketimines.
Copper complexes are of interest as precursors for the preparation of thin copper films. Creation of such metallic films, for example by chemical vapor deposition or atomic layer deposition, could be used in the manufacture of a wide variety of electronic devices.
Hexafluoroacetylacetonato(trimethylsilylethylene)copper(I), (D. Bollmann, R. Merkel, and A. Klumpp Microelectronic Eng. 1997, 37/38, 105, and reference there-in) has been widely tested for this application, but the presence of oxygen and fluorine in this precursor may be detrimental to the desired performance, including device efficiency (P. Motte, M. Proust, J. Rorres, Y. Gobil, Y. Morand, J. Palleau, R. Pantel, M. Juhel Microelectronic Eng. 2000, 50, 369). Volatile, oxygen- and halogen-free complexes of copper are desired.
Alternative ligands, such as 1,3-diketimines, have also been investigated as metal complex precursors for microchip interconnect layers. Preparation of symmetrically substituted 1,3-diketimines and their homoleptic metal complexes of the form ML2 have been described by S. G. McGeachin (Canadian Journal of Chemistry, 1968, 46, 1903-1912).
U.S. Pat. No. 6,939,578 discloses methods for preparing copper complexes derived from both N,N′-symmetrical and N,N′-unsymmetrical 1,3-diimine ligands. The N,N′-unsymmetrically substituted 1,3-diimines are expected to be more volatile than their symmetrically substituted counterparts, due to the less compacted mode of molecular stacking originating from the unsymmetrical ligand.
DE 2,707,658 and U.S. Pat. No. 4,130,652 describe the preparation of monocyclic 1,3-diketimines having aromatic substituents in the presence of acid.
K-. H. Park (J. of Organic Chemistry, 2005, 70, 2075-2081) discloses the preparation of N,N′-substituted 1,3-diketimines in the presence of base.
One embodiment of this invention provides a process for the synthesis of N,N′-substituted 1,3-diketimines (III) from the reaction of aliphatic ketimines (I) with iminothioethers (II) in the presence of base.
One embodiment of this invention is a process comprising:
a. reacting R3N═C(R1)CH2R5 with an alkali metal or alkaline earth metal base in a polar aprotic solvent to form a metalloenamine, [R3NC(R1)CHR5]−M+, where M is an alkali metal or an alkaline earth metal;
b. reacting the metalloenamine with R6SC(R2)═NR4 to form a 1,3-diketiminate salt; and
c. treating the diketiminate salt with a protic solvent to form a 1,3-diketimine, R3N═C(R1)C (R5)═C(R2)NHR4,
wherein
R1 is selected from the group consisting of C1-C5 linear alkyl groups and C6-C12 aryl groups; and
R3 and R5 are independently selected from the group consisting of hydrogen, C1-C5 linear alkyl groups and C6-C12 aryl groups; or
(R1, R3) or (R1, R5) taken together are (CR7R8)m, where R7 and R8 are independently selected from the group consisting of hydrogen and C1-C5 alkyl, and m is 3, 4 or 5;
R2 and R4 are independently selected from the group consisting of hydrogen and C1-C5 alkyl groups and C6-C12 aryl groups; or
(R2, R4) taken together are (CR9R10)n, where R9 and R10 are independently selected from the group consisting of hydrogen and C1-C5 alkyl, and n is 3, 4 or 5; and
R6 is selected from a group consisting of C1-C10 alkyl and C6-C10 aryl groups.
Applicant has discovered an efficient synthesis of N,N′-substituted 1,3-diketimines that may be used to make metal precursors with sufficient volatility to be useful in CVD or ALD processes for the deposition of thin metal films. This process is especially useful for making aliphatic N,N′-unsymmetrically substituted 1,3-diketimines.
In one embodiment of this invention, the desired 1,3-diketimines (III) are obtained substantially pure from the reaction of ketimines (I) with iminothioethers (II) in the presence of base.
One embodiment of this invention is a process comprising:
a. reacting R3N═C(R1)CH2R5 with an alkali metal or alkaline earth metal base in a polar aprotic solvent to form a metalloenamine, [R3NC(R1)CHR5]−M+, where M is an alkali metal or an alkaline earth metal;
b. reacting the metalloenamine with R6SC(R2)═NR4 to form a 1,3-diketiminate salt; and
c. treating the diketiminate salt with a protic solvent to form a 1,3-diketimine, R3N═C(R1)C (R5)═C(R2)NHR4,
wherein
R1 is selected from the group consisting of C1-C5 linear alkyl groups and C6-C12 aryl groups; and
R3 and R5 are independently selected from the group consisting of hydrogen, C1-C5 linear alkyl groups and C6-C12 aryl groups; or
(R1, R3) or (R1, R5) taken together are (CR7R8)m, where R7 and R8 are independently selected from the group consisting of hydrogen and C1-C5 alkyl, and m is 3, 4 or 5;
R2 and R4 are independently selected from the group consisting of hydrogen and C1-C5 alkyl groups and C6-C12 aryl groups; or
(R2, R4) taken together are (CR9R10)n, where R9 and R10 are independently selected from the group consisting of hydrogen and C1-C5 alkyl, and n is 3, 4 or 5; and
R6 is selected from a group consisting of C1-C10 alkyl and C6-C10 aryl groups.
If any of the R groups, R1-R10, is an alkyl or aryl group, it can be either substituted or unsubstituted. Suitable substitutents include alkylsilyl groups, arylsilyl groups, ether groups, alkyl groups, aryl groups, haloaryl groups and CF3-substituted aryl groups.
In the process of this invention, an aliphatic ketimine (I) is deprotonated by a base in a polar, aprotic solvent. Suitable bases include alkali or alkaline earth metal hydrides such as NaH or CaH2, lithium alkylamides such as lithium diisopropylamide, lithium hexamethyidisilazane, sodium hexamethyldisilazane, alkyl lithiated bases such as butyl lithium, aryl lithiated bases such as phenyl lithium, and alkylmagnesium halides such as methylmagnesium bromide.
Suitable polar aprotic solvents for the deprotonation reaction include tetrahydrofuran, ether, dimethoxyethane, dioxane, and diglyme.
The metalloenamine from ketimine (I) reacts with the electrophile iminothioether (II), providing a 1,3-diketiminate metal salt, which is protonated by protic solvent. Suitable solvents for the protonation of 1,3-diketiminate salt include, but are not limited to water, methanol, ethanol, and propanol.
In one embodiment of this invention, ketimine (I) is added dropwise to a mixture of the sodium or lithium base in the aprotic solvent at −78° C. to 0° C. under an inert atmosphere. After stirring the mixture at this temperature for 0.5 hr to 2 hr, iminoether (II) is added dropwise at at −78° C. to 0° C. under an inert atmosphere. The temperature is allowed to increase to room temperature over a period of 2-6 hours and the resultant mixture is stirred for 2 days. The reaction mixture is concentrated under reduced pressure, and then protic solvent is slowly added to the residue. After removing the solvent under reduced pressure, a nonpolar hydrocarbon solvent such as pentane or hexane is added to the residue. The mixture is filtered, then after concentration of the filtrate under reduced pressure, the product is isolated by vacuum distillation.
In other embodiments of this invention, the solution of base is added dropwise to ketimine (I). Similarly, the solution of the metalloenamine, [R3NC(R1)CHR5]−M+, can be added dropwise to the iminoether (II).
Ketimines useful in the process of this invention can be synthesized by the reaction of ketone derivatives with amines. For example, acetone and isobutylamine are mixed together in the presence of acid catalyst such as hydrochloric acid to provide the ketimine (I), N-isopropylideneisobutylamine, as described by W. H. Bunnelle (Synthesis 439, (1997)).
Similarly, iminothioethers can be synthesized by the alkylation of thioamide derivatives with alkylating agents such as iodomethane or Meerwein's salt, as described in M. A. Casadei (Synthetic Communication, 1983, 20, 753-759).
Unless otherwise stated, all organic reagents are available from Sigma-Aldrich Corporation (Milwaukee, Wis., USA). The ketimines (I) and iminothioethers (II) were prepared by methods described by W. H. Bunnelle ibid. and M. A. Casadei ibid., respectively.
To a solution of diisopropylamine (10.29 g, 101.8 mmol, 2.1 eq) in THF (200 mL) was added n-BuLi (35.2 mL, 101.8 mmol, 2.1 eq, 2.89 M in hexane) dropwise at −78° C. The deprotonation mixture was stirred at −78° C. for 30 min, then stirred at −10° C. for another 30 min. Then, a solution of N-isopropylideneisobutylamine, I (wherein R1=Me, R3=isobutyl, R5=hydrogen), (7.13 g, 63 mmol, 1.3 eq) in THF (20 mL) was added dropwise to the deprotonation mixture at −10° C. After stirring the resulting mixture for 40 min at −10° C., methyl N-methylthioacetimidate, (5 g, 48.45 mmol) solution in THF (15 mL) was added to the mixture dropwise at −10° C. The resultant mixture was stirred overnight as the temperature was allowed to gradually rise to room temperature. The reaction mixture was concentrated under reduced pressure, then MeOH (30 mL) was slowly added to the residue. After removing the solvent under reduced pressure, pentane (100 mL) was added to the residue. The mixture was filtered, then the filtrate was concentrated under reduced pressure, followed by vacuum distillation (35° C., 72 mtorr) to afford desired product (4.3 g, 53%) as a colorless oil. 1H NMR (500 MHz, C6D6) δ 11.41 (s, br, 1H), 4.62 (s, 1H), 2.94 (d, 2H, J=6.6 Hz), 2.82 (s, 3H), 1.77 (m,1H), 1.71 (s, 3H), 1.66 (s, 3H), 0.94 (d, 6H, J=6.4 Hz); 13C NMR (125 MHz, C6D6) δ 161.9, 159.8, 95.1, 54.6, 33.4, 30.4, 20.7, 19.4, 18.9.
To the solution of diisopropylamine (10.29g, 101.8 mmol, 2.1 eq) in THF (200 mL) was added n-BuLi (46.3 mL, 101.8 mmol, 2.1 eq, 2.2 M in hexane) dropwise at −78° C. The mixture was stirred at −78° C. for 30 min, then stirred at −10° C. for another 30 min. Then, N-isopropylideneisobutylamine (7.13g, 63 mmol, 1.3 eq) solution in THF (20 mL) was added dropwise to the mixture at −10° C. After stirring the mixture for 40 min at the same temperature, 2-methylthio-1-pyrroline (5.58 g, 48.45 mmol) solution in THF (15 mL) was added to the mixture dropwise at −10° C. The resultant mixture was stirred overnight as the temperature was allowed to gradually rise to room temperature. The reaction mixture was concentrated under reduced pressure, then MeOH (20 mL) was slowly added to the residue. After removing the solvent under reduced pressure, pentane (120 mL) was added to the residue. The mixture was filtered, then the filtrate was concentrated under reduced pressure, followed by vacuum distillation (54° C., 102 mtorr) to afford desired product (5.8 g, 66%) as a colorless oil. 1H NMR (500 MHz, CDCl3) δ 9.92 (s, br, 1H), 4.54 (s, 1H), 3.82 (t, 2H, J=7.1 Hz), 2.98 (d, 2H, J=6.7 Hz), 2.46 (t, 2H, J=8.0 Hz), 1.90 (s, 3H), 1.77-1.69 (m, 3H), 0.92 (d, 6H, J=7.3 Hz); 13C NMR (125 MHz, CDCl3) δ 173.9, 154.4, 87.3, 60.1, 51.0, 37.7, 29.6, 22.4, 20.0, 19.1.
To the solution of diisopropylamine (24 g, 237 mmol, 2.1 eq) in THF (400 mL) was added n-BuLi (108 mL, 237 mmol, 2.1 eq, 2.2 M in hexane) dropwise at −78° C. The mixture was stirred at −78° C. for 30 min, then stirred at −10° C. for another 30 min. Then, 2-methyl-3,4,5,6-tetrahydropyridine (14.3 g, 147 mmol, 1.3 eq) solution in THF (20 mL) was added dropwise to the mixture at −10° C. After stirring the mixture for 40 min at the same temperature, 2-methylthio-1-pyrroline (13 g, 112.8 mmol) solution in THF (20 mL) was added to the mixture dropwise at −10° C. The resultant mixture was stirred overnight as the temperature was allowed to gradually rise to room temperature. The reaction mixture was concentrated under reduced pressure, then MeOH (100 mL) was slowly added to the residue. After removing the solvent under reduced pressure, pentane (200 mL) was added to the residue. The mixture was filtered, then the filtrate was concentrated under reduced pressure, followed by vacuum distillation (58° C., 46 mtorr) to afford desired product (16 g, 86%) as an oil. 1H NMR (500 MHz, CD2Cl2) δ 9.08 (s, br, 1H), 4.49 (s, 1H), 3.78 (t, 2H, J=7.1 Hz), 3.27 (t, 2H, J=6.0 Hz), 2.46 (t, 2H, J=7.9 Hz), 2.34 (t, 2H, J=6.7 Hz), 1.73 (m, 2H), 1.67 (m, 2H); 13C NMR (125 MHz, CD2Cl2) δ 173.9, 156.1, 87.0, 60.2, 42.0, 38.0, 29.6, 23.9, 22.8, 21.5.
To a solution of diisopropylamine (11.1 g, 109.7 mmol) in THF (200 mL) was dropwise added n-BuLi (2.89 M, 37.97 mL, 109.7 mmol) at −78° C. under nitrogen. Once all the n-BuLi was added, the temperature was adjusted to −5° C., and the reaction mixture was stirred for 30 min. Then a solution of 2-methyl-1-pyrroline (5.65 g, 67.9 mmol) in THF (15 mL) was added dropwise to the reaction mixture at −5° C., and then stirred. After 30 min, 2-methylthio-1-pyrroline (6.02 g, 52.3 mmol) was added dropwise over 30 min at −78° C. The reaction mixture was stirred as the temperature was allowed to gradually rise to room temperature, and was continuously stirred at room temperature overnight. THF solvent was removed under reduced pressure, then 50 mL of methanol was added dropwise to the residue. After removing all of the volatile solvent, pentane (2×100 mL) was added to the residue, and the mixture was filtered. Concentration of the filtrate under reduced pressure, followed by vacuum distillation (65° C. at 110 mtorr), delivered 6.2 g of product (79%). 1H NMR (CD2Cl2, 500 MHz): δ 7.89 (s, br, 1H), 4.65 (s, 1H), 3.64 (t, 2H, J=7.2 Hz), 2.51 (t, 2H, J=8.0 Hz), 1.85 (m, 2H). 13C NMR (CD2Cl2, 125 MHz): δ 167.0, 81.7, 53.7, 34.8, 23.2.
