Polyfluoroaryl organometallic compounds. Part IV. Fluorocarbon derivatives of tricovalent aluminium

Abstract

Pentafluorophenylaluminium dibromide and bis(pentafluorophenyl)aluminium bromide have been prepared by cleavage of methylpentafluorophenylmercury with aluminium tribromide. The bromides are both essentially dimeric in benzene and the stability of the compounds, formally three-covalent, is attributed to a combination of bromine bridging and internal p–π bonding; the latter is indicated by ¹⁹F n.m.r. measurements. Pentafluorophenyl-aluminium dibromide can be sublimed, with some disproportionation, but no Al–F bonds are formed, although at higher temperatures explosive decomposition occurs. Some reactions of pentafluorophenylaluminium dibromide are described, as well as unsuccessful attempts to prepare tris(pentafluorophenyl)aluminium.