Stable chlorine trifluoride dioxide

Abstract

Chlorine trifluoride dioxide is disclosed for use as an oxidizer in formulating energetic compositions, such as propellants. The stable ClF.sub.3 O.sub.2 is produced by reacting a ClO.sub.2 F.sub.2 .sup.+ salt with a strong Lewis base at -78.degree. C.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to compositions of matter and is particularly directed to chlorine trifluoride dioxide and a method of producing the same.

2. Prior Art

Energetic compositions of matter are useful in providing energy sources for rocket engines, guided missiles, auxiliary power units for aircraft, ordnance, demolition and the like. Such compositions conventionally are produced by mixing a fuel with an oxidizer. Obviously, the energy of such compositions results primarily from the oxidation of the fuel. Hence, it is desirable to provide a highly energetic oxidizing agent. On the other hand, it is equally desirable that the oxidizing agent be a stable material, so as to prevent accidental or unintentional ignition or explosive decomposition of the composition. Numerous organic and inorganic compounds have been proposed heretofore for use as such oxidizing agents. However, it has been found that, as a general rule, stable compounds are low energy oxidizers and high energy oxidizers are unstable. Thus, although some useful oxidizing agents have been disclosed by the prior art, the search for a stable, high-energy, oxidizing material has continued. In recent years, studies have indicated that halogen oxyfluoride materials might provide a satisfactory oxidizing material. However, although empirical formulas may be stated for such materials and some of the properties of such materials may be predicted, the synthesis of these materials has proven to be extremely difficult and it is sometimes found that several materials, each having distinct structures and properties, are defined by a single empirical formula. Thus, U.S. Pat. No. 3,285,842 discloses a process for producing a material which was believed to have the empirical formula chlorine trifluoride dioxide, ClF.sub.3 O.sub.2, which the patent states to be a violet liquid which is unstable at temperatures above -72.degree. C. It was subsequently shown, however, that this composition does not contain the chemical compound ClF.sub.3 O.sub.2, but consists of a mixture of chlorine fluorides and oxygen fluorides (K. O. Christe, R. D. Wilson, and I. B. Goldberg, J. Fluor-Chem., 7,543 (1976). This fact readily explains the great difference in physical and chemical properties between the composition and the novel composition disclosed in this invention. While it would be expected that the previously claimed composition would also be a highly energetic oxidizing agent, the lack of stability renders it unsafe for use in the production of propellants and the like.

Brief Summary and Objects of Invention

These disadvantages of the prior art are overcome with the present invention and a composition of matter is disclosed which based on its chemical structure truly is chlorine trifluoride dioxide. It is sufficiently stable at +25.degree. C. and, hence, can be safely employed for manufacturing propellants and the like. In addition, a method is disclosed for producing chlorine trifluoride dioxide by reacting ClF.sub.2 O.sub.2.sup.+ PtF.sub.6.sup.- with a strong Lewis base at a temperature of about -78.degree. C. and separating the products of the reaction by distillation.

Accordingly, it is an object of the present invention to provide a new composition of matter having the chemical composition ClF.sub.3 O.sub.2.

An additional object of the present invention is to provide a method of producing chlorine trifluoride dioxide.

A specific object of the present invention is to provide chlorine trifluoride dioxide by reacting ClF.sub.2 O.sub.2.sup.+ salts with nitryl fluoride at a temperature of about -78.degree. C. and separating the products of the reaction by distillation.

These and other objects and features of the present invention will be apparent from the following detailed description.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

In that form of the present invention chosen for purposes of illustration, chlorine trifluoride dioxide has been produced by reacting a ClF.sub.2 O.sub.2 .sup.+ salt, such as ClF.sub.2 O.sub.2 .sup.+PtF.sub.6 .sup.-, with a strong Lewis base at -78.degree. C.

EXAMPLE I

A sample of ClO.sub.2 .sup.+PtF.sub.6 .sup.- containing about 10% of ClF.sub.2 O.sub. 2 .sup.+PtF.sub.6 .sup.- was treated at -78.degree. C. in a sapphire reactor with a large excess of FNO for several days. No material noncondensible at -196.degree. C. (i.e., F.sub.2) was observed. The products, volatile at 25.degree. C. were removed and separated by fractional condensation through a series of traps kept at -126.degree. C., -142.degree. C., and -196.degree. C. The -142.degree. C. fraction contained a novel compound which was identified by its infrared spectrum as ClF.sub.3 O.sub.2. The observed frequencies are listed in Table I and are in excellent agreement with those expected for a trigonal bypyramidal structure of symmetry C.sub.2v. ##STR1## This structure was confirmed by .sup.19 F nuclear magnetic resonance spectroscopy. The observed signal consisted of a typical AB.sub.2 pattern centered at -413 ppm relative to the external standard CFCl.sub. 3. The F-F coupling constant was measured to be 443 Hz. The B.sub.2 part of the AB.sub.2 pattern occurs downfield from the A part, proving that the B.sub.2 fluorine atoms occupy the two axial positions. Additional structural proof was obtained from the Raman spectrum of the gas and the liquid showing strong absorptions at 1096, 684, 548, 527, 493, 290, and 229 cm.sup..sup.-1. The molecular weight of the compound was confirmed by vapor density measurements (measured, 122; calculated, 124). These data establish beyond doubt (see K. O. Christe and R. D. Wilson, Inorg. Chem, 12, 1356 (1973) and K. O. Christe and E. C. Curtis, Inorg. Chem. 12, 2245 (1973) that contrary to the previous claim (U.S.P. 3,285,842) our novel composition has indeed the chemical composition ClF.sub.3 O.sub.2.

Table I______________________________________Infrared Spectrum of ClF.sub.3 O.sub.2 and its Tentative AssignmentFrequency Assignment for Point(cm.sup.-.sup.1) Intensity Group C.sub.2v______________________________________1334 s .nu..sub.10 (B.sub.2), .nu.asCl0.sub.21096 s .nu..sub.1 (A.sub.1), .nu.symCl0.sub.2699 vs .nu..sub.7 (B.sub.1), .nu.asClF.sub.2 Ax687 vs v.sub.2 (A.sub.1), .nu.ClF598 ms .nu..sub.11 (B.sub.2), .delta.rock ClO.sub.2543)532) mw .nu..sub.3 (A.sub.1) and .nu..sub.8______________________________________ (B.sub.1) The solid residue obtained from the FNO displacement reaction showed the correct weight change expected for conversion into NO.sup.+PtF.sub.6 .sup.-. Its identity as NO.sup.+PtF.sub.6 .sup.- was confirmed by infrared spectroscopy.

The chlorine trifluoride dioxide is white as a solid having a melting point of about -81.2.degree. C. and colorless as a liquid having a boiling point of about -21.degree. C. It is marginally stable at 25.degree. C. The observed stability and lack of color furthermore demonstrate that our product cannot be identical with the previously reported deeply violet and unstable ClF.O.sub.2 F.sub.2 and ClF.sub.3.O.sub. 2 addition compounds supposedly having the empirical composition ClF.sub.3 O.sub.2.

EXAMPLE II

A sample ClO.sub.2 .sup.+PtF.sub.6 .sup.- containing about 10% of ClO.sub.2 F.sub.2 .sup.+PtF.sub.6 .sup.- was treated with a sufficient quantity of FNO.sub.2 to maintain a liquid phase at -78.degree. C. in a stainless steel reactor for up to 12 hours. This reaction yielded solid NO.sub.2 .sup.+PtF.sub.6.sup.- and gaseous ClF.sub.3 O.sub.2 plus FClO.sub.2. If desired, the chlorine trifluoride dioxide may then be separated by conventional distillation techniques, as in a multi-plate distillation tower.

Small amounts of material were purified by combining the ClF.sub.3 O.sub.2 and FClO.sub.2 at -196.degree. C. with a small excess of BF.sub.3. These materials were allowed to mix and warm to ambient temperature. This results in ClF.sub.2 O.sub.2 .sup.+BF.sub.4 .sup.-, which is stable, plus ClO.sub.2 .sup.+BF.sub.4 .sup.-, which has a dissociation pressure of 182 millimeters at 22.degree. C. and which can be removed by pumping. The ClF.sub.2 O.sub.2 .sup.+BF.sub.4 .sup.- is then reacted with sufficient FNO.sub.2 to maintain a liquid phase at -78.degree. C. for up to 12 hours. This reaction produced solid NO.sub.2 .sup.+BF.sub.4 .sup.- plus gaseous ClF.sub.3 O.sub.2 and FNO.sub.2. The two gases may be pumped off and separated by passing the gases through a pair of traps maintained at -126.degree. C. and -196.degree. C., respectively. The chlorine trifluoride dioxide will be caught in the -126.degree. C. trap.

Obviously, numerous variations and modifications may be made without departing from the present invention. Accordingly, it should be clearly understood that the forms of the present invention described above are illustrative only and are not intended to limit the scope of the present invention.

Claims

1. A new composition of matter consisting of chlorine trifuloride dioxide, ClF.sub.3 O.sub.2, having the structure ##STR2## having the infrared spectrum set forth in the following Table,

Table I______________________________________Infrared Spectrum of ClF.sub.3 O.sub.2 and its Tentative AssignmentFrequency Assignment for Point(cm.sup.-.sup.1) Intensity Group C.sub.2v______________________________________1334 s .nu..sub.10 (B.sub.2), .nu.asCl0.sub.21096 s .nu..sub.1 (A.sub.1), .nu.symCl0.sub.2699 vs .nu..sub.7 (B.sub.1), .nu.asClF.sub.2 Ax687 vs v.sub.2 (A.sub.1), .nu.ClF598 ms .nu..sub.11 (B.sub.2), .delta.rock ClO.sub.2543)532) mw .nu..sub.3 (A.sub.1) and .nu..sub.8______________________________________ (B.sub.1)

and being a white solid which melts at about -81.degree. C. to a colorless liquid and boils at about -21.degree. C. and is stable up to about +25.degree. C.