N.sub.2 F.sub.3 SbF.sub.6 and its preparation

Abstract

N.sub.2 F.sub.4 and SbF.sub.5 react in anhydrous HF to produce N.sub.2 F.sub.3 SbF.sub.6. The salt is useful as a burn rate modifier in NF.sub.3 -F.sub.2 gas generators.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the salt N.sub.2 F.sub.3 SbF.sub.6 and to its preparation.

2. Description of the Prior Art

The use of solid compositions to produce fluorine and NF.sub.3 for chemical lasers is known. For example, Pilipovich in U.S. Pat. No. 3,963,542, describes such a composition. The need for burn rate modifiers for solid gas generating compositions is also well known.

SUMMARY OF THE INVENTION

According to this invention, a salt that is useful as a burn rate modiifier for NF.sub.3 -F.sub.2 gas generators is provided. The salt is a fluorine containing salt having the formula N.sub.2 F.sub.3 SbF.sub.6 and is prepared by reacting N.sub.2 F.sub.4 and SbF.sub.5 in anhydrous HF. Insofar as is known by the inventors, N.sub.2 F.sub.3 SbF.sub.6 has not been previously synthesized.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The preparation of the salt of this invention is illustrated by the following example.

EXAMPLE

Synthesis of N.sub.2 F.sub.3 SbF.sub.6. A Teflon ampule, containing a Teflon coated magnetic stirring bar and equipped with a stainless steel valve, was loaded with 14.4 mmol of SbF.sub.5 in a glovebox. The ampule was then attached to a vacuum line and 2 ml of anhydrous HF was condensed into the ampule at -78.degree. C. while stirring and warming to ambient temperature. The system was then pressurized with N.sub.2 F.sub.4 (1 atm). A gradual decrease in the pressure was noted due to uptake of N.sub.2 F.sub.4. Periodic cycling to below 0.degree. C. seemed to increase the rate of N.sub.2 F.sub.4 uptake. After several hours the unreacted N.sub.2 F.sub.4 and HF solvent were pumped off at 40.degree. C. until constant weight was achieved. The observed weight gain corresponded to the reaction of 12.1 mmol of N.sub.2 F.sub.4. When the reaction was repeated on a larger scale with 8 ml HF for 3 days, it was found that 74.0 mmol of SbF.sub.5 reacted with 73.5 mmol of N.sub.2 F.sub.4 to give 23.66 g of N.sub.2 F.sub.3 SbF.sub.6 (weight calcd for 74.0 mmol of N.sub.2 F.sub.3 SbF.sub.6 23.74 g), which was characterized by .sup.19 F NMR and vibrational spectroscopy.

Tests in which small amounts of N.sub.2 F.sub.3 SbF.sub.6 were incorporated into aluminized NF.sub.3 -F.sub.2 gas generator compositions showed that the salt was effective as a burn rate modifier.

Claims

1. The salt having the formula:

N.sub.2 F.sub.3 SbF.sub.6.

2. A method for preparing the salt having the formula N.sub.2 F.sub.3 SbF.sub.6 comprising the steps of:

forming a solution of N.sub.2 F.sub.4 and SbF.sub.5 in anhydrous HF; and

reacting the N.sub.2 F.sub.4 and SbF.sub.5 at room temperature.

3. A method according to claim 2 wherein the HF solvent is removed by distillation.