Half-Sandwich Zirconium and Hafnium Amidoborane Complexes: Precursors of Hydride Derivatives.

Half-sandwich zirconium(IV) and hafnium(IV) complexes with amidoborane and hydride ligands have been isolated in the stoichiometric reactions of mono(pentamethylcyclopentadienyl)metal alkyl and amido derivatives with the amine-boranes NHRBH (R = H, Me, HBu). Treatment of the tris(trimethylsilylmethyl) complexes [M(η-CMe)(CHSiMe)] with NHBH (3 equiv) gives the seven-coordinate species [M(η-CMe)(NHBH)] (M = Zr (), Hf ()) with three κ-NHBH ligands. The tris(neophyl) [M(η-CMe)(CHCMePh)] or tris(dimethylamido) [M(η-CMe)(NMe)] derivatives react with NHMeBH (≥3 equiv) to afford bis(dimethylamidoborane) hydride complexes [M(η-CMe)H(NMeBH)] (M = Zr (), Hf ()) via thermally unstable [M(η-CMe)(NMeBH)] species.