An Aluminum Dihydride Working as a Catalyst in Hydroboration and Dehydrocoupling

The well-defined aluminum dihydride
LAlH2 (L = HC­(CMeNAr)2, Ar = 2,6-Et2C6H3) (1) operates in catalysis
like a transition metal complex.
The catalytic activity of 1 for hydroboration of terminal
alkynes was investigated. Furthermore, catalyst 1 effectively
initiated the dehydrocoupling of boranes with amines, thiols, and
phenols, respectively, to form compounds with B–E bonds (E
= N, S, O) under elimination of H2. Quantum mechanical
calculations indicate that hydroboration and dehydrocoupling reactions
occur via three consecutive cycloaddition reactions involving the
activation of the X–H (X = Al, B, C, and O) σ-bonds.