Stabilization of nickel(O) by hemilabile P,N-ferrocene ligands and their ethylene oligomerization activities

Abstract

Ligand displacement reactions of Ni(COD)2 with a ferrocenediyl iminophosphine, viz., [C5H4CH= N(C6F 5)]Fe[η-C5H4PPh2] (1) or [C 5H4CH=NC(H)(CH3)(C4H 5)]Fe[η-C5H4PCy2] (2), in the presence of t-BuNC, CO, or PhC≡CPh give the appropriate mixed-ligand Ni(0) complexes, viz., [C5H4CH= N(C6F 5)]Fe[η-C5H4PPh2]Ni 0(CNt-Bu)3 (3), [C5H4CH=N(C 6F5)]Fe[η-C5H4PPh 2]Ni0(CO)2 (4a), {[C5H 4CH=N(C6F5)]Fe[η-C5H 4PPh2]}2Ni0(CO)2 (4b), and [C5H4CH=NC(H)(CH3)(C6H 5)]Fe[η-C5H4PCy2]Ni 0(η2 PhC≡CPh) (5). The X-ray crystal and molecular structures of 4b and 5 are described. The hemilability of iminophosphine is illustrated by the formation of both P,N-chelating and imine-pendant functions. All the complexes examined are catalytically active toward ethylene oligomerization at 30°C, with 5 showing the best activity, followed by 3 and 4. © 2006 American Chemical Society.