Tetrafluoroammonium Hexafluoroantimonate V

The low-temperature UV photolysis reaction is carried out in a quartz reactor with a pan-shaped bottom and a flat top consisting of a 7.5-cm diameter optical grade quartz window (Fig. 1). The vessel has a side arm connected by a Teflon 0-ring joint to a Fischer-Porter Teflon valve to facilitate removal of solid reaction products. The depth of the reactor is about 4 cm, and its volume is about 140 mL. The UV source consists of a 9(X)-W, air-cooled, high-pressure mercury arc (General Electric Model B-H6) positioned 4 cm above the flat reactor surface. The bottom of the reactor is kept cold by immersion in liquid Nj. Dry, gaseous N2 is used as a purge gas to prevent condensation of atmospheric moisture on the flat top of the reactor. As a heat shield, a 6-mm-thick quartz plate is positioned between the UV source and the top of the reactor. 

Premixed NFj [Air Products] and BFj [Matheson] (27 mmol of each) are condensed into the cold bottom of the quartz reactor. Fluorine [Air Products] (9 mmol) is added, and the mixture is photolyzed at —196° for 1 hr. After termination of the photolysis, volatile material is pumped out of the reactor (through a scrubber ) during its warm-up to room temperature. The nonvolatile white solid residue (1.0 g) is pure [Np4][BF4]. Instead of the pan-shaped reactor, a simple round quartz bulb can be used with a [NF4][Bp4] yield of about 0.3 g/ hr. 

A mixture of dry CsF [Kawecki Berylco] (2.361 g, 15.54 mmol) and [NFJfSbFs] (5.096 g, 15.64 mmol) is placed inside the dry box into trap I of the leak-checked and passivated (with CIF3 and dry HF ) Teflon FEP Monel metathesis apparatus shown in Fig. 2. The CsF is dried by fusion in a platinum crucible, immediately transferred to the dry box, cooled, and finely ground. The apparatus is attached to a metal Teflon vacuum system by two flexible corrugated Teflon tubes [Penntube Plastics], and the connections are vacuum leak-checked and passivated. The system is repeatedly exposed to anhydrous HF [Matheson], until the HF is colorless when frozen out at —196° in a Teflon U-trap of the vacuum system to avoid contamination of the product with any chlorine fluorides that may be adsorbed onto the walls of the metal vacuum system. Anhydrous HF (16.2 g, 810 mmol) is added to trap I, and the mixture is stirred magnetically for 1 hr at room temperature. The metathesis apparatus is cooled with powdered Dry Ice to — 78° for 1 hr and then inverted. The HF solution that contains the 

An unstable solid having the composition [NF4][HF2] HF (n = 2-10) can be prepared by pumping off as much HF as possible below 0°. 

Tetrafluoroammonium (hydrogen difluoride) is stable in HF solution at room temperature but decomposes to NFj, F2, and HF on complete removal of the solvent. The F NMR spectrum of the solution shows a triplet of equal intensity of 4 216.2 ppm downfield from CFCI3 with 7nf = 230 Hz. The Raman spectrum of the HF solution has bands at 1170 (w), 854 (vs), 612 (m), and 448 (mw) cm . 

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