Germyliumylidene: A Versatile Low Valent Group 14 Catalyst

Abstract 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 [MesTerGe(NHC)2]Cl (1), (MesTer=2,6‐(2,4,6‐Me3C6H2)2C6H3; 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.