N-Heterocyclic carbene phosphaketene adducts as precursors to carbene-phosphinidene adducts and a rearranged π-system

The nucleophilic attack of NHCs on the electron deficient carbon of tetryl substituted phosphaketenes Ph3E-P = C = O (E = Sn-Si), leads quantitatively to the formation of NHC-phosphaketene adducts. With E = Sn or Ge, these zwitterionic adducts decompose upon thermolysis under the release of carbon monoxide to give zwitterionic NHC-phosphinidene adducts. With E = Si an OCP to CPO rearrangement occurs which leads to the formation of a linear p-conjugated molecule, NHC = C = P-O-SiPh3.