A nuclear magnetic resonance investigation of some gallium trihalide complexes

Abstract

The methyl and methylene proton chemical shifts of diethyl ether, diethyl sulphide, and their liquid 1:1 complexes with gallium trichloride and tribromide have been measured and compared with the known heats of formation of these complexes; it is shown that the change in chemical shift on complexing is not a reliable criterion of stability in these compounds. However, displacement equilibrium constants can be reliably determined by n.m.r. and these parallel the thermochemical data. Deviations from linearity in the plots of chemical shift against mixing ratio, [GaX₃]/[Ligand], have been used to estimate the formation constants of the individual complexes, and trends in these values are consistent with trends in the calorimetrically determined heats of formation. In these systems gallium trichloride is a stronger acceptor than gallium tribromide and diethyl sulphide is a stronger ligand than diethyl ether.