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)

Abstract

The complexes NiBr2(L2) [L2 = (mim)2CO (7a), (bim)2CO (7b), py(mim)CO (8), PhN=CHbim (9)], NiBr(o-Tol){(mim)2CO} (10), Ni(L2)(o-Tol)(PPh3) [L2 = mimCO2- (11a); bmCO2- (11b), mimCPh2O- (12), mimC6H4O- (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)(PPh3)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(OH2)]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.