Sterically demanding iminopyridine ligands

Two sterically demanding iminopyridine ligands, (2,6-diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridin-2-ylmeth- ylene]amine and (2,6-diisopropylphenyl)]6-(2,6-dimethylphenyl)pyridin-2-ylmethylene]amine, were prepared by a two-step process: first, condensation of 6-bromopyridine-2-carbaldehyde with an equimolecular amount of 2,6-diisopropylaniline, and second, Kumada-type coupling of in-situ-formed Grignard compounds of 1-bromo-2,6-dimethylphenyl and 1-bromo-2,4,6-triisopropylphenyl. Dichlorido complexes of the ligands were synthesized starting from FeCl2, [PdCl2(cod)], [NiCl2(dme)], and CoCl2 (cod = 1,5-cyclooctadiene, dine = dimethoxyethane). X-ray crystal structure analyses of a Fe, Pd, and Co complex were determined. Ethylene polymerization/oligomerization behavior of the dichlorido complexes after activation with methyl duminoxane or triethylaluminum was studied. Ethylene dimerization selectivity greater than 95% was observed. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)