Exploring the coordination chemistry of N-heterocyclic phosphenium/phosphido ligands using nickelocene as a synthon

Abstract

Treatment of the N-heterocyclic chlorophosphine precursor (PPP)Cl (1) with two equivalents of nickelocene (NiCp2) affords the phosphorus-bridged dimer [(μ-PPP)Ni2Cp2]Cl (2). In contrast, an equimolar mixture of 1 and NiCp2 in the presence of PPh3 generates a different product, (PP(C5H5)P)NiCl2 (3), in which a cyclopentadienyl anion has migrated to the N-heterocyclic phosphenium center. The phosphorus-bound Cp ring in complex 3 has undergone a [1,5]-hydride shift to afford a vinylic C5H5− ring, and can be subsequently deprotonated to produce [(PP(C5H4)P)NiCl] (4).