A stable heavier group 14 analogue of vinylidene

Vinylidene (H₂C=C) is a member of the family of compounds of composition CH (and isomeric with ethyne, HC≡CH), but it has been observed only transiently-with a lifetime in the region of 0.1 ns. Indeed, no simple (non-base-stabilized) compounds of the type R₂E=E have been characterized structurally for any of the group 14 elements. Here we show that by employing the bulky and strongly electron-donating boryl ligand (HCDippN)₂B (Dipp, 2,6-ⁱPr₂C₆H₃), a simple monomeric digermavinylidene compound, (boryl)₂GeGe, can be synthesized and is stable at room temperature. Both its formation via the two-electron chemical oxidation of the symmetrical Ge⁰ compound K₂[(boryl)GeGe(boryl)] and its subsequent reaction chemistry (for example, with H₂), are consistent with a high substituent lability and the accessibility of both 1,1- and 1,2-substitution patterns. Structural and computational studies of [(HCDippN)₂B]₂GeGe reveal a weak Ge-Ge double bond-the π component of which contributes to the highest occupied molecular orbital (HOMO)-with a Ge-centred lone pair as the HOMO-1.