Complexing and exchange of boron, aluminum, and gallium chlorides with some Lewis bases

Abstract

Boron trichloride and dimethyl sulfide form a 1:1 complex. It exchanges with excess boron trichloride by a displacement mechanism with an activation energy of 5.0 ± 0.5 kcal/mol and with excess dimethyl sulfide by a dissociation mechanism which has an activation energy of 20 ± 1 kcal/mol. The 1:1 complex of AlCl3 and dimethyl sulfide exchanges very rapidly with excess dimethyl sulfide. Equilibria and exchange reactions of AlCl3[(CH3)2O], AlCl3[(CH3)2O]2, and (CH3)2O are described. Rapid exchange is always found in the analogous gallium systems. BCl3 reacts with chloride ion to give BCl4− and B2Cl7−, which exchange rapidly with excess BCl3. AlCl3 reacts with Cl− and BCl4− to give AlCl4− which does not exchange with AlCl3.