A Bis(germaamidine) through Nitrene Insertion into Ge─Si Bonds

Abstract

Amidines (with two nitrogen atoms around the unsaturated carbon center) are important synthetic building blocks. In particular, phenylene-bridged derivatives are extensively used in the synthesis of cyclic and polymeric structures for pharmaceutical, electrochemical, and materials applications. While various heavier Group 14 congeners of the related imines and guanidines (with one nitrogen less or more, respectively) are known, only one case of an amidine with a SnN bond has been reported. Herein, a bis(germaamidine) with the two germaamidine moieties connected by a silylene-phenylene linking unit is presented. Azide-induced GeGe double bond cleavage in the bridged bis(digermene) precursor results in the concomitant formation of two equivalents of a tetraazagermole by-product. NMR spectroscopic monitoring and the isolation of an intermediately occurring aziridine suggest the initial formation of a bis(germaimine), followed by the insertion of transient nitrene into the GeSi bonds. This is further confirmed by comparative reactions of the Ge(II) centers of the corresponding bis(germylene)-carbene adducts with the azide. Reactions of the bis(germaamidine) with CO2 and MeOH result in additions to the GeN bonds, suggesting significant potential as a bifunctional monomer for the synthesis of poly(germane)s.