Organoaluminium compounds. XVI. The mechanism of exchange between trimethylaluminium and triphenylaluminium in the presence of pyridine

The kinetics of exchange of a methyl group of trimethylaluminiunl for a phenyl group of triphenylaluminium have been studied by the use of proton magnetic resonance (p.m.r.) spectroscopy. An excess of pyridine was always present. Results obtained using a large excess support a bimolecular mechanism without loss of pyridine from the organoaluminium complexes prior to exchange. When the excess of pyridine is small, the rate of exchange depends on the concentration of excess pyridine. Here reaction may proceed by a mechanism in which loss of pyridine from one of the organoaluminium complexes occurs prior to exchange.