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 (NiCp 2 ) affords the phosphorus-bridged dimer [(µ-PPP)Ni 2 Cp 2 ]Cl (2). In contrast, an equimolar mixture of 1 and NiCp 2 in the presence of PPh 3 generates a different product, (PP(C 5 H 5 )P)NiCl 2 (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 C 5 H 5 ring, and can be subsequently deprotonated to produce [(PP(C 5 H 4 )P)NiCl] (4).