Exploring Ligand Effects on Structure, Bonding, and Photolytic Hydride Transfer of Cationic Gold(I) Bridging Hydride Complexes of Molybdocene and Tungstenocene.

A diverse family of heterobimetallic bridging hydride adducts of the type [LAu(μ-H)MCp][X] (L = 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene, IPr; 1,3-bis(1-adamantyl)imidazole-2-ylidene, IAd; 1,3-bis(2,6-di--propylphenyl)-5,5-dimethyl-4,6-diketopyrimidinyl-2-ylidene, DAC; triphenylphosphine, PPh; 2-di--butylphosphino-2',4',6'-triisopropylbiphenyl, XPhos; X = SbF, BF or TfO) was synthesized by reacting group VI metallocene dihydrides CpMH (Cp = cyclopentadienyl anion; M = Mo, W) with cationic gold(I) complexes [LAu(NCMe)][X]. Trimetallic [L'Au(μ-H)WCp][X] and tetrametallic [L'Au{(μ-H)WCp}] [X] complexes (L' = -2,2'-bis(diphenylphosphino)-1,1'-binaphthalene or bis(diphenylphosphinomethane)) were obtained by reacting digold [L'{Au(NCMe)}][X] with CpWH in a 1:1 and a 1:2 stoichiometry. Accessing such a broad structural diversity allowed us to pinpoint roles played by the ancillary ligands and group VI metals on the bonding properties of this family of bridging hydrides.