Germyliumylidene: A Versatile Low Valent Group 14 Catalyst.

Bis-NHC stabilized germyliumylidenes [RGe(NHC)2 ]+ are typically Lewis basic (LB) in nature, owing to their lone pair and coordination of two NHCs to the vacant p-orbitals of the germanium center. However, they can also show Lewis acidity (LA) via Ge-CNHC σ* orbital. Utilizing this unique electronic feature, we report the first example of bis-NHC-stabilized germyliumylidene [Mes TerGe(NHC)2 ]Cl (1), (Mes Ter=2,6-(2,4,6-Me3 C6 H2 )2 C6 H3 ; NHC= IMe4 =1,3,4,5-tetramethylimidazol-2-ylidene) catalyzed reduction of CO2 with amines and arylsilane, which proceeds via its Lewis basic nature. In contrast, the Lewis acid nature of 1 is utilized in the catalyzed hydroboration and cyanosilylation of carbonyls, thus highlighting the versatile ambiphilic nature of bis-NHC stabilized germyliumylidenes.