Gallane-coordinated transition metal complexes and related compounds

The gallane-Lewis base adduct H3Ga·L is employed as a σ-Ga–H ligand for the group 6 carbonyl metal complexes (OC)5M(H3Ga·L) (M = Cr, Mo, W) and the manganese complex Cp*(OC)2Mn(H3Ga·L). Group 6 carbonyl metal derivatives (OC)5M(H3Ga·L) are synthesized by the reaction of (OC)5M(THF) and H3Ga·L. The photochemical reaction of Cp*(OC)3Mn and H3Ga·L affords the gallane manganese σ-complex Cp*(OC)2Mn(H3Ga·L). The structural properties of these complexes can be understood in terms of the coordination mode of σ-Ga–H bond to (OC)5M and Cp*(OC)2Mn fragments being depicted as η1-HGaH2·L and η2-HGaH2·L, respectively. The contribution of σ-donation from the Ga–H σ-bond to dσ orbital on M occurs in both systems, however, the participation of π-back donation from filled dπ orbital to Ga–H σ* orbital is negligible for the (OC)5M(H3Ga·L) complexes but important for Cp*(OC)2Mn(H3Ga·L) complex. Such distinctive characteristics of the σ-H3Ga·L ligand provides a sharp contrast to that of H3B·L and silane ligands.