Synthesis and characterisation of trimethylsilyl phosphorohalidates: Me3SiOP(O)FX (X = Cl, Br) and (Me3SiO)2P2O3F2

Trimethylsilyl phosphorochloridofluoridate, Me3SiOP(O)FCl, has been prepared by reaction of POFCl2 with hexamethyldisiloxane or by treatment of bis(trimethylsilyl) phosphorofluoridate with phosphorus pentachloride. The compound could be purified by vacuum distillation and has been isolated in 55% yield. The ester Me3SiOP(O)FBr is formed in an analogous reaction of POFBr2 with (Me3Si)2O, however its susceptibility to spontaneous decomposition makes its isolation unfeasible. Condensation of Me3SiOP(O)FCl with (Me3SiO)2P(O)F or heating of POFBr2 with excess hexamethyldisiloxane gave bis(trimethylsilyl) diphosphorodifluoridate, (Me3SiO)2P2O3F2, in 45–53% yield. The existence of both expected diastereoisomers was revealed by 19F and 31P NMR spectroscopy.