Metal Activation of a Germylenoid, a New Approach to Metal–Germanium Triple Bonds: Synthesis and Reactions of the Germylidyne Complexes [Cp(CO)₂MGe–C(SiMe₃)₃] (M = Mo, W)

The reactions of the germylenoid Li­(THF)3GeCl2C­(SiMe3)3 with the carbonyl metalates Li­[CpMo­(CO)3] and K­[CpW­(CO)3] (Cp = η5-C5H5) in toluene afford selectively the germylidyne complexes [Cp­(CO)2MGe–C­(SiMe3)3] (1-Mo, M = Mo; 1-W, M = W). The compounds 1-Mo and 1-W rapidly add 1,3,4,5-tetramethylimidazol-2-ylidene (Im-Me4) at the electrophilic germanium center to give the zwitterionic germylidene complexes [Cp­(CO)2MGe­(Im-Me4)­{C­(SiMe3)3}] (2-Mo, M = Mo; 2-W, M = W). The molecular structures of 1-Mo/1-W and 2-Mo/2-W were determined by single-crystal X-ray diffraction studies, and the structural and spectroscopic features of all complexes are discussed.