Metal nitrene-like reactivity of a SiN bond towards CO2

Abstract

The unusual reactivity of the SiN bond in metallo-iminosilane [DippN = Si(OSiMe₃)Ni(Cl)(NHC)₂] 1 towards CO₂ and cyclohexyl isocyanate (CyNCO) is reported; it reacts with two molar equiv. of CO₂ to give the [2+2+2] cycloaddition product 3 with complete scission of the σ- and π-Si–N bonds akin to transition-metal nitrene complexes. Theoretical calculations indicate that this reaction is made viable by the high polarity of the Si–N interaction in the intermediary [2+2] cycloaddition product 2, which could also be crystallographically characterised. In the case of isocyanate, the [2+2] cycloaddition product of the CO and SiN bonds is formed exclusively.