Organoaluminium compounds. XV. The mechanism of the exchange reaction between Lewis-base complexed (CH₃)₂AlX and (CH₃)₂AlY

Abstract

Kinetic studies have been made by proton magnetic resonance spectroscopy of exchange reactions between trimethylaluminium and dimethylaluminium bromide, trimethylaluminium and dimethylaluminium chloride, trimethyl-aluminium and dimethylphenylaluminium, and (iv)dimethylaluminium chloride and dimethylaluminium bromide. An excess of anisole was present in all four cases. In reactions (i), (ii), and (iii) the exchange rates were strongly dependent upon excess anisole, but that of (iv) was only slightly dependent. The exchange between dimethylaluminium chloride and dimethylaluminium bromide was also studied using an excess of ether and no dependence of rate upon excess ether was found. It is proposed that: (a) for (i), (ii), and (iii) removal of base from one of the organoaluminium compounds occurs prior to exchange; (b) exchange between dimethylaluminium chloride and dimethylaluminium bromide in the presence of ether proceeds without loss of base from either organoaluminium complex ; (c) for reaction (iv) exchange occurs partly with and partly without prior loss of base.