A Germanium(II) Hydride as an Effective Reagent for Hydrogermylation Reactions

Herein we report on the reactivity of the stable germanium(II) hydride LGeH (L = CH{(CMe)(2,6-iPr2C6H3N)}2) (2), which contains a low-valent germanium atom. 2 is prepared from the corresponding germanium(II) chloride LGeCl (1) using H3Al·NMe3 or K[HB(iBu)3] in toluene. The reaction of 2 with carbon dioxide in toluene at room temperature affords a germanium(II) ester of formic acid, LGe−O−C(O)H (3), which is formed by insertion of the carbon dioxide into the germylene hydrogen bond. 2 also reacts with alkynes at room temperature to give the first germanium(II)-substituted alkenes (4, 5, and 6). These two reaction types have in common the fact that the hydrogen and germylene from LGeH are transferred to an unsaturated bond: the carbon−oxygen double bond (CO) in the former case and the carbon−carbon triple bond (CC) in the latter. Moreover, the reaction of 2 with elemental sulfur in toluene at room temperature leads to the germanium dithiocarboxylic acid analogue LGe(S)SH (7). Compound 7 is formed by the unprecedented insertion of elemental sulfur into the germylene hydrogen bond and oxidative addition of elemental sulfur to the germanium(II) atom. This leads to the formal conversion of the GeH hydride to a SH proton. Compounds 3−7 were investigated by microanalysis, multinuclear NMR spectroscopy, and single-crystal X-ray structural analyses.