Stable nickel catalysts for fast norbornene polymerization:: Tuning reactivity

The air-stable complexes trans-[Ni(C6Cl2F3)(2)L-2] (L = SbPh3, 1; AsPh3, 2; AsCyPh2, 3; AsMePh2, 4; PPh3, 5) have been synthesized by arylation of [NiBr2(dme)] (dme = 1,2-dimethoxy-ethane) in the presence of the corresponding ligand L (for compounds 1-4) or by ligand substitution starting from 1 (for compound 5). The structures of 1, 2, and 5 have been determined by X-ray diffraction and show an almost perfect square-planar geometry in all cases. Their catalytic activity in insertion polymerization of norbornene have been tested showing a strong dependence of the yield and molecular mass of the polymer on the ligand used and the solvent. High yield and high molecular mass values are obtained using complexes with ligands easy to displace from Ni-II (SbPh3 is the best) and noncoordinating solvents. Complexes 1-3 are suggested as convenient bench-catalysts to have available in the lab. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)