Aluminium-27 n.m.r. studies of aluminium fluoro complexes in dichloromethane solution: evidence for tetrafluoroaluminate anion

Mixed aluminium chloro/fluoro anions are formed in dichloromethane solution by the interaction of AlCl3 and [Ph3PhCH2P] [H2F3]. Aluminium-27 n.m.r. studies are restricted to the stoichiometric ranges F/Al from 1:1 to 3:1 and F/Al>8:1. Between these limits rapid precipitation reactions occur. In the fluoride-rich stoichiometric range there is rapid exchange on the n.m.r. time scale between the aluminium fluoro anion and free fluoride, so that a direct identification of the species by the multiplicity of the resonance is not possible. Indirect evidence strongly suggests that the aluminium species is [AlF4]-. In the F/Al stoichiometry range from 1:1 to 3:1 aluminium-27 resonances were observed for all the other possible [AlClχF4-χ]- species. Studies on the aluminium iodo/fluoro system support the identification of [AlF4]-, but the system is labile and the mixed iodo/fluoro species undergo rapid disproportionation. 12 refs., 1 fig