Synthesis of nickel(II) complexes containing neutral N,N´ and anionic N,O- bidentate ligands, and their behaviour as chain-growth catalysts; structural characterisation of complexes containing (mim)2CO, mimCO2-, and mimCPh2O- (mim = 1-methylimidazol-2-yl)

The complexes NiBr2(L2) [L2 = (mim) 2CO (7a), (bim)2CO (7b), py(mim)CO (8), PhNCHbim (9)], NiBr(o-Tol){(mim)2CO} (10), Ni(L2)(o-Tol)(PPh3) [L2=mimCO2-(11a),bmCO2-(11b), mimCPh2O- (12), mimC 6H4O- (13)], and [Ni{(mim)2CO} 3][BF4]2 · 0.25H2O (16) have been synthesised from nickel(II) salts (7-9, 16) or NiBr(o-Tol)(PPh 3)2 [10-13], where mim = 1-methylimidazol-2-yl, bim = 1-benzylimidazol-2-yl, and py = pyridin-2-yl. The square-planar complexes (11a, 12) and octahedral 16 have been characterised by X-ray diffraction studies, together with octahedral cis-[Ni{(mim)2CO}2Br(OH 2)]Br · CD3CN (14) and cis-[Ni{(mim) 2CO}2(OH2)2]Br2 · 3CD3CN (15). Preliminary catalytic studies have been undertaken with a number of the nickel complexes. Complexes 11-13 form single component catalysts for the oligomerization or polymerization of ethylene and the bromo-complexes (7-9) form active catalysts for the oligomerization or polymerization of ethylene when activated with MMAO. © 2004 Elsevier B.V. All rights reserved.