Substituent Effects in (K2-N,O)-Salicylaldiminato Nickel(II)-Methyl Pyridine Polymerization Catalysts: Terphenyls Controlling Polyethylene Microstructures

A series of (κ2-N,O)-salicylaldiminato Ni(II)-methyl pyridine complexes 7-pyr and 8-pyr derived from 3,5-diiodosalicyaldehyde (3a) and 3-(9-anthryl)salicylaldehyde (3b), and terphenylamines 2,6-(3,5R-4-R′-C6H2)2C6H3-NH2 (4a, R ) CF3, R′ ) H; 4b, R ) tBu, R′ ) H; 4c, R ) tBu, R′ ) OH; 4d, R ) Me, R′ ) H; 4e, R ) Me, R′ ) MeO; 4f, R ) MeO, R′ ) H; 4g, R ) MeO, R′ ) MeO), was prepared by reaction of the respective salicylaldimine (5a-f, 6a-g) with [(tmeda)Ni(CH3)2] (tmeda ) N,N,N′,N′tetramethylethylenediamine) or [(pyridine)2Ni(CH3)2]. Complexes 7-pyr and 8-pyr are highly active single component catalysts for the polymerization of ethylene, producing a wide range of different polyethylene microstructures. While comparable complexes derived from 3a, 3b, 5-nitrosalicylaldehyde, 3-tertbutylsalicylaldehyde, 3,5-[3,5-(CF3)2C6H3]2-salicylaldehyde, and 2,6-[3,5-(CF3)2C6H3]2C6H3-NH2 afford polyethylenes with similar degrees of branching, variation of the terphenyl moieties in complexes 7-pyr and 8-pyr allows access to a wide range of polyethylene microstructures under identical reaction conditions. The X-ray diffraction analyses of complexes 7b-pyr and 8f-pyr are reported.