Activation of the Olefinic C–H Bond of NHC and NHO by Perimidine-Based Silicon and Germanium Compounds

In this manuscript, several backbone germylene-functionalized zwitterionic compounds were prepared conveniently from the corresponding N-heterocyclic carbenes or N-heterocyclic olefins in a single step through backbone C–H activation. Our initial motivation was to generate a silylene from C10H6(Me3SiN)2SiHCl (2) using ItBu [ItBu = (1,3-ditert-butyl)­imidazol-2-ylidene], but instead, the reaction led to deprotonation from the imidazolium backbone of ItBu, forming the imidazolium salt with a silyl backbone at the C4 position (3). We presumed that the reaction proceeded through the generation of an ephemeral silylene. We subsequently prepared the analogous germylene (4) and reacted it with IDipp [IDipp = 1,3-bis­(2,6-diisopropylphenyl)­imidazol-2-ylidene], ItBu, and IDipp=CH2. Spectroscopic and crystallographic analysis of these complexes revealed that, in all cases, there was deprotonation from the backbone and formation of zwitterionic products (5–7). When the hydrogen in the NHC backbone was replaced with methyl groups such as IDippMe (1,3-bis­(2,6-diisopropylphenyl)-4,5-dimethylimidazol-2-ylidene), simple adduct formation occurred, exemplified by the isolation of IDippMe·Ge­(NSiMe3)2C10H6 (8).