Synthesis of a Molybdenum Hydrido(hydrogermylene) Complex and Its Conversion to a Germylyne Complex: Another Route through Dehydrogenation with Nitriles

A molybdenum germylene complex having Mo-H and Ge-H bonds, Cp*(CO)₂(H)Mo=Ge(H){C(SiMe₃)₃} (1), was synthesized by the reaction of a methyl molybdenum complex with a trihydrogermane and was converted to a germylyne complex, Cp*(CO)₂MoGe{C(SiMe₃)₃} (2), via dehydrogenation with aryl isocyanates under mild heating. A similar conversion from the same germylene complex into the germylyne complex also occurred using nitriles instead of isocyanates, while releasing imines via a Mo-Ge-N three-membered ring complex Cp*(CO)₂Mo[κ²(N,Ge)Ge-(N=CHR){C(SiMe₃)₃}] (4, R = Me and aryl groups) as an intermediate. Formation of imines was confirmed by a trapping experiment with BPh₃, which afforded a BPh₃-imine adduct. In the case of aryl nitriles, the corresponding three-membered ring intermediates were converted into the germylyne complex efficiently by blue LED light irradiation. TD-DFT calculations on the three-membered-ring intermediate suggest that the role of the LED light is to induce CO ligand dissociation from the intermediate via a metal-to-ligand-charge-transfer (MLCT) transition.