Metal-halogen bonding studies with group IV A trialkylmetal halides

Abstract Halogen redistribution reactions have been found to take place between benzyl bromide or benzyl iodide and the Group IVA silicon, germanium, tin, and lead containing triakylmetal chlorides. However, for the reactions of the Si, Ge and Sn compounds, a quaternary ammonium halide catalyst was necessary to enable the equilibria to be established at reasonably rapid rates. The equilibrium constants at 50°C have been measured for each at these halogen redistributions. They have been found to increase gradually on going down in Group IV A from silicon to lead, being considerably less than unity in the case of silicon and somewhat greater than unity in the case of lead for both the R 3 MCl + BzBr and R 3 MCl + BzI reactions. The Δ G ° values for these equilibria have been calculated, and it is suggested that their differences may be explained in terms of the relative importance of p π d π contributions to the halogen—metal bonding in the various Group IV A trialkylmetal halide systems.