A Guanidine‐Supported π‐Complex of Germanium Amenable to Intramolecular C−C Cleavage in Arene and Ge Atom Transfer

The germylone dimNHCGe (dimNHC=diimino N‐heterocyclic carbene) reacts with azides N 3 R (R=SiMe 3 or p‐ tolyl) to furnish the first examples of germanium π‐complexes, i. e. guanidine‐ligated compounds (dimNHI−SiMe 3 )Ge (NHI=N‐heterocyclic imine, R=SiMe 3 ) and (dimNHI−Tol)Ge (R=p‐tolyl). DFT calculations suggest that these species are formed by a Staudinger type replacement of dinitrogen in the azide by a nucleophilic germylone, leading to a transient carbene adduct of iminogermylidene. Heating a solution of compound (dimNHI−SiMe 3 )Ge to 70 °C results in extrusion of the iminogermylidene that further aggregates to produce the known [Me 3 SiNGe] 4 tetramer, whereas the imidazolylidene fragment transforms into an unusual heptatriene species that can be considered as a product of carbene insertion into the C−C bond of a pendant Ar substituent at the imidazolylidene nitrogen of the dimNHC. Reaction of (dimNHI−SiMe 3 )Ge with tetrachloro‐ o ‐benzoquinone results in the net transfer of a germanium atom and formation of the free diimino‐guanidine ligand. This ligand also forms when (dimNHI−SiMe 3 )Ge is treated with azide N 3 (p−Tol), with the germanium product being [(p−Tol)NGe] n