Reactions between organic derivatives of group III elements and acids

Abstract

The cyanides Me(_2)MCN(M = Al, Ga, In or Tl) were prepared from the trimethylmetal and hydrogen cyanide. In contrast to the polymeric boron cyanides, RgBCN, the aluminium, gallium, and indium compounds are tetrameric in benzene, and dimethylthallium cyanide is a salt in aqueous solution. Reactions between dimethylberyllium (and its trimethylamine complex) and hydrogen cyanide were also investigated. The phosphinates, thiophosphinates, sulphinates, one arsinate and carboxylates of many of the Group III metals were prepared from reactions between the triraethylmetal and the corresponding acid in an inert solvent (ether or benzene). These were sufficiently volatile to be purified by vacuum sublimation. The compounds were air-sensitive. Molecular weights were determined cryoscopically in benzene and the compounds were found to be dimers. The structures of these dimers were established on the basis of their infrared spectra, as eight-membered ring compounds in which the P = 0 or similar groups participated in co-ordinate bond formation. The dithiophosphinates of aluminium, gallium and indium were prepared from reactions between the trimethylmetal and dimethyldithiophosphinic acid in an inert solvent. These were purified by vacuum sublimation as colourless crystals. Molecular weights were determined cryoscopically in benzene and the compounds were found to be monomers (compare the phosphinates, sulphinates etc. which were found to be dimers). Bimethylaluminium methane-sulphonate and the corresponding gallium compound were prepared by similar reactions. They were purified by vacuum sublimation as white crystalline solids. Molecular weights were determined cryoscopically in benzene and the compounds were found to be trimers. The infrared spectra of all the compounds prepared were investigated and several new assignments for different structural features were made.