NHC-induced conversion of a W-Ge double bond into the triple bond through formation of W-Ge single and double bonded intermediates

Reaction of hydrido(hydrogermylene) complex Cp*(CO)(2)(H) W - Ge(H)(Tsi) (1, Tsi - C(SiMe3)(3)) with 1 equiv of (IMe)-I-Me ((IMe)-I-Me = 1,3-dimethyl-4,5-dimethylimidazol-2-ylidene) immediately afforded NHCstabilized germylene complex Cp*(CO)(2)(H) WGe(H)((IMe)-I-Me)(Tsi) (2) that has a zwitterionic, We-Ge single-bonded structure. Complex 2 was thermally unstable and intramolecular proton-transfer followed by hydride-transfer to the NHC-unit occurred slowly at room temperature to give anionic germylene complex [Cp*(CO)(2)W = Ge(H)(Tsi)][(HIMe)-I-Me] ([3][(HIMe)-I-Me]) first and subsequently germylyne complex Cp*(CO)(2)W= Ge(Tsi) (4) and H-2 MeIMe. Although [3][(HIMe)-I-Me] was too unstable to be isolated, the salt of bulkier [(HIPr)-I-Me-Pr-i](+), [Cp*(CO)(2)W = Ge(H)(Tsi)][(HIPr)-I-Me-Pr-i] ([3][(HIPr)-I-Me-Pr-i]), was thermally more stable and was isolated and fully characterized. (C) 2017 Elsevier B.V. All rights reserved.