Characterisation of the tetrahalophosphonium cations PBrnI4-n+ (0 <= n <= 4) by P-31 MAS NMR, IR and Raman spectroscopy and the crystal structures ofPI4+AlCl4-, PI4+AlBr4- and PI4+GaI4-

The novel tetrahalophosphonium salts PBr4+AsF6-, PI4+AlCl4- and PI4+EBr4- ( E = Al, Ga) have been synthesised. A variety of solid complexes containing PBr4+ (e.g. PBr4+AsF6-, PBr4+AlBr4- PBr4+GaBr4-), PI4+ (e.g. PI4+AlCl4-, PI 4+AlBr4-, PI4+GaBr4-) or the mixed species PBrnI4 epsilon-epsilonn+ (0 less than or equal to n less than or equal to 4,containing AlBr4-, GaBr4-, AsF6 - or SbF6-) have been studied by solid-state P-31 MAS NMR and vibrational s pectroscopy. The influence of the counter-ion on the chemical shift and the vibrational frequencies are discussed. The crystal structures of PI4+AlCl4 -, PI4+AlBr4- and PI4+GaI4- are reported. Evidence for the existence of the hitherto unknown mixed bromoiodophosphonium cations PBr3I+, PBr2I2+ and PB rI3+ has been confirmed by spin-orbit corrected density functional calculat ions of isotropic P-31 chemical shifts for PBrnI4 - n+.