The Preparation and Properties of Complexes of Antimony and Bismuth Trifluorides with Strong Fluoride Acceptors

Abstract

The reactions of antimony and bismuth trifluorides with the pentafluorides of antimony and arsenic in liquid sulfur dioxide yield the adducts SbF 3 •SbF 5 (type A), SbF 3 •AsF 5 , BiF 3 •3SbF 5 , and BiF 3 •AsF 5 ; no adducts of the trifluorides with BF 3 were isolated. Antimony metal reacts with excess of antimony pentafluoride and arsenic pentafluoride in liquid sulfur dioxide giving a second form of SbF 3 •SbF 5 (type B) and the same form of SbF 3 •AsF 5 as produced from SbF 3 , respectively. BiF 3 •3SbF 5 can be formulated as Bi(SbF 6 ) 3 , but its Raman spectrum indicates the presence of extensive cation–anion fluorine-bridging. Their Raman spectra suggest that BiF 3 •AsF 5 , SbF 3 •AsF 5 , and SbF 3 •SbF 5 (type B) have similar structures, possibly containing polymeric fluorine-bridged cations, but that SbF 3 •SbF 5 (type A) has a different structure probably like that of AsF 3 •SbF 5 . The 121 Sb Mössbauer spectra of the SbF 3 adducts support the assignment of similar structures to SbF 3 •AsF 5 and SbF 3 •SbF 5 (type B), and the suggestion that SbF 3 •AsF 5 and both forms of SbF 3 •SbF 5 contain antimony (III) fluoro-cations. 19 F n.m.r. shows that SbF 3 has appreciable solubility in SO 2 solutions of SbF 5 and indicates the possible formation of "fluxional" SbF 2 –Sb n F 5n+1 molecules in SbF 3 –SbF 5 solutions.