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 = S, O) under elimination of H-2. 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) sigma-bonds.