Synthesis and reactivity of N-heterocyclic carbene (NHC)-supported heavier nitrile ylides.

The synthesis and isolation of stable heavier analogues of nitrile ylide as N-heterocyclic carbene (NHC) adducts of phosphasilenyl-tetrylene [(NHC)(Ar)Si(H)PE(Ar)] (E = Ge 1, Sn 2; Ar = 2,6-MesCH, NHC = IMe) are reported. The delocalized Si-P-E π-conjugation was examined experimentally and computationally. Interestingly, the germanium derivative 1 exhibits a 1,3-dipolar nature, leading to an unprecedented [3 + 2] cycloaddition with benzaldehyde, resulting in unique heterocycles containing four heteroatoms from group 14, 15, and 16. Further exploiting the nucleophilicity of germanium, activation of the P-P bond of P was achieved, leading to a [(NHC)(phosphasilenyl germapolyphide)] complex. Moreover, the [3 + 2] cycloaddition and the σ-bond activation by 1 resemble the characteristics of the classic nitrile ylide.