Silagermylenation of CO bonds and radical fragmentation of CO2-expanded bis(germylene) by a cyclic (alkyl)(amino)carbene

Abstract

The transformation of the greenhouse gas CO2 into value-added products represents a major contemporary challenge. Low-valent p-block compounds typically react at the oxygen termini of CO2 due to the oxophilicity of the metal centers. We now report on the selective activation of CO2 and ethyl isocyanate at the central carbon atom by an N-heterocyclic carbene (NHC)-stabilized para-silylenephenylene-bridged bis(germylene). During the net silagermylenation, the C[double bond, length as m-dash]X (X = O, NEt) bonds are inserted into the Ge–Si bonds through cooperativity of the low-valent metal center and the electrophilic silyl backbone. The germanium(II) centers are retained in the products, as is confirmed by multinuclear NMR data, IR spectroscopy and X-ray analysis and supported by DFT calculations. Attempts to substitute the NHCs by cyclic (alkyl)(amino)carbenes (CAACs) resulted in a germylene-CAAC radical by homolytic cleavage of the Si–O bonds as evidenced by single crystal X-ray diffraction and continuous-wave EPR spectroscopy.