Germyl- and Germylene-Bridged Complexes of Rh/Ir and Subsequent Chemistry of a Bridging Germylene Group

A series of neutral and cationic germylene-bridged complexes and a neutral germyl­(germylene) complex have been synthesized and characterized by NMR spectroscopy and X-ray crystallography. Reaction of 1 equiv of primary germanes, RGeH3 (R = Ph, tBu), with [RhIr­(CO)3(dppm)2] (1) at low-temperature yields [RhIr­(GeH2R)­(H)­(CO)3(dppm)2] (R = Ph (3) or tBu (4)), the products of single Ge–H bond activation, which upon warming transform to the germylene-bridged dihydrides, [RhIr­(H)2(CO)2(μ-GeHR)­(dppm)2] (R = Ph (5) or tBu (6)) by activation of a second Ge–H bond accompanied by CO loss. Both classes of compounds have the diphosphines folded back in a “cradle-shaped” geometry. Although compound 5 reacts with additional phenylgermane at −40 °C to give a germylene-bridged/germyl product, [RhIr­(GeH2Ph)­(H)2(CO)2(κ1-dppm)­(μ-GeHPh)­(μ-H)­(dppm)] (7), warming results in decomposition. However, reaction of 5 with 1 equiv of diphenylgermane at ambient temperature results in a novel mixed bis­(μ-germylene) complex, [RhIr­(CO)2(μ-GeHPh)­(μ-GePh2)­(dppm)2] (8), containing both mono- and disubstituted germylene fragments. Reaction of 1 equiv of diphenylgermane with complex 1 produces a similar monogermylene-bridged product, [RhIr­(H)2(CO)2(μ-GePh2)­(dppm)2] (9), while reaction of 1 with 2 equiv of diphenylgermane yields the germyl/germylene product [RhIr­(H)­(GeHPh2)­(CO)3(κ1-dppm)­(μ-GePh2)­(dppm)] (10). The above reactions, incorporating first one and then a second equivalent of primary and secondary germanes, were studied by low-temperature multinuclear NMR spectroscopy, revealing details about the stepwise activations of multiple Ge–H bonds. Reaction of diphenylgermane with the cationic complex [RhIr­(CH3)­(CO)2(dppm)2]­[CF3SO3] (2) leads to a cationic A-frame-type germylene- and hydride-bridged product, [RhIr­(CO)2(μ-H)­(μ-GePh2)­(dppm)2]­[CF3SO3] (3), which reversibly activates H2, yielding a germyl-bridged dihydride and reacts stoichiometrically with water, methanol, and HCl to yield the respective germanol, germamethoxy, and germylchloride products.