Bis(N-heterocyclic olefin) Derivative: An Efficient Precursor for Isophosphindolylium Species.

We have developed bis(N-heterocyclic olefin) derivatives 2 and demonstrated that 2 can be utilized as precursors for the synthesis of isophosphindolylium species 3. X-ray diffraction and density functional theory studies indicate the aromatic property of the PC4 five-membered ring in 3. Despite its cationic nature, the P center in 3b exhibits nucleophilic character and thus readily forms a bond with CuCl to afford a copper phosphenium complex 4, demonstrating the potential utility of 3 as a σ-donor ligand.