Electron rich bidentate phosphinimine-imine ligands: Synthesis and reactivity of late transition metal complexes

Abstract

Electron rich phosphinimine-imine proligands Ph₃PN(C₆H₄)C(Ph)(NAr) (L_Ar) (Ar = 4-(OEt)C₆H₄ (OEt), 3,5-Me₂C₆H₃(Xyl)) were synthesized in three steps from 2-aminobenzophenone. These compounds, along with previously reported L_Mes and L_Tol (Mes = 2,4,6-Me₃C₆H₂, Tol = 4-MeC₆H₄) were used to synthesize a series of tetracarbonyltungsten(0) complexes: L_MesW(CO)₄ (1), L_TolW(CO)₄ (2), L_OEtW(CO)₄ (3), and L_XylW(CO)₄ (4). The ligands were evaluated by analysis of the carbonyl stretching frequencies of the tungsten complexes and were shown to be better σ-donors and poorer π-acceptors compared to similar ligands in the literature. The coordination chemistry of the proligands was expanded to other late transition metals and L_MesCoCl₂ (5), L_TolCoCl₂ (6), L_MesNiBr₂ (7), L_TolNiBr₂ (8), L_MesZnCl₂ (9), and L_TolZnCl₂ (10) were synthesized by the direct reaction of L_Mes and L_Tol with the respective metal dihalide precursors. The complexes were fully characterized and the molecular structures of complexes 3, 6, 7, and 10 were reported. The synthesis of zinc complexes 9 and 10 was dependent on the steric bulk of the ligand. Complex 10 proved to be resistant to derivatization via a number of routes.