Stabilization of Nickel(0) by Hemilabile P,N-Ferrocene Ligands and Their Ethylene Oligomerization Activities

Ligand displacement reactions of Ni(COD) 2 with a ferrocenediyl iminophosphine, viz., [C 5 H 4 CH N(C 6 F 5 )]Fe[η-C 5 H 4 PPh 2 ] ( 1 ) or [C 5 H 4 CH NC(H)(CH 3 )(C 6 H 5 )]Fe[η-C 5 H 4 PCy 2 ] ( 2 ), in the presence of t -BuNC, CO, or PhC⋮CPh give the appropriate mixed-ligand Ni(0) complexes, viz., [C 5 H 4 CH N(C 6 F 5 )]Fe[η-C 5 H 4 PPh 2 ]Ni 0 (CN t -Bu) 3 ( 3 ), [C 5 H 4 CH N(C 6 F 5 )]Fe[η-C 5 H 4 PPh 2 ]Ni 0 (CO) 2 ( 4a ), {[C 5 H 4 CH N(C 6 F 5 )]Fe[η-C 5 H 4 PPh 2 ]} 2 Ni 0 (CO) 2 ( 4b ), and [C 5 H 4 CH NC(H)(CH 3 )(C 6 H 5 )]Fe[η-C 5 H 4 PCy 2 ]Ni 0 (η 2 -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 .