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

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.