Controlled hydrolysis of AlMe 3 to tetramethylalumoxane and a new look at incipient adducts with water.

We present an efficient route to tetramethylalumoxane by the controlled hydrolysis of AlMe 3 in the presence of pyridine. The AlMe 3 (pyr) hydrolysis by 0.5 and 1 equiv. of H 2 O has been followed with real-time 1 H NMR. Based on high-level quantum-chemical calculations, we conclude that hypervalent, pentacoordinate aluminium species are critical in the first steps of hydrolysis.