C–H and H–H Bond Activation by a Cationic Germylyne Complex

Abstract

Reactivities of a cationic germylyne complex [Cp*(CO)2W≡Ge(IPr)](BAr4F) (1) [IPr = 1,3-bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene] toward several unsaturated organic substrates and dihydrogen were investigated. Complex 1 underwent activation of the formyl C–H bond of benzaldehyde and the ortho C–H bond of pyridine to afford base-stabilized germylene complexes, indicating that coordination of the heteroatom (O/N) of the substrates to the Lewis acidic Ge center facilitates the C–H bond activation on W. The reactions with alkenes resulted in the terminal C–H bond cleavage on Ge by coordination of the C═C double bond to W, giving η3-germaallyl complexes. The reactions with terminal alkynes, on the contrary, proceeded through no C–H bond cleavage to produce metallacyclopropenylgermylenes, which have an unprecedented bonding situation with a lone pair on Ge. Complex 1 also reacted with dihydrogen at room temperature to afford a dihydrido(dihydrogermyl) complex finally through a hydrido(hydrogermylene) complex. Characterization of these products including X-ray crystal diffraction study (XRD) and possible reaction mechanisms based on cooperative action at the W–Ge unsaturated bond platform are described.