Reactions of boron compounds with difluorophosphoric acid; characterisation of the tetrakis(difluorophosphato)borate anion by multinuclear (11B, 19F, and 31P) nuclear magnetic resonance spectroscopy

Abstract

The tetrakis(difluorophosphato)borate anion, [B(PO₂F₂)₄]^–(1), has been identified and characterised in solution by means of ¹¹B, ¹⁹F, and ³¹P n.m.r. spectroscopy. (1) is formed from H₃BO₃ and P₂O₃F₄ in HPO₂F₂. It is also the initial product of the reaction of BBr₃ or BCl₃ with excess HPO₂F₂; however, it is gradually converted to (2), which is believed to be [BF(PO₂F₂)₃]^–. (2) is also generated directly from either BF₃ or BF₄^– in P₂O₃F₄–HPO₂F₂ mixtures, in which it is gradually converted to (1).