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, [formula omitted], and mimCPh 2O − (mim = 1-methylimidazol-2-yl)

Abstract

The complexes NiBr 2(L 2) [L 2 = (mim) 2CO ( 7a), (bim) 2CO ( 7b), py(mim)CO ( 8), PhN CHbim ( 9)], NiBr( o-Tol){(mim) 2CO} ( 10), Ni(L 2)( o-Tol)(PPh 3) [ L 2 = mimCO 2 - ( 11 a ) , bmCO 2 - ( 11 b ) , mimCPh 2O − ( 12), mimC 6H 4O − ( 13)], and [Ni{(mim) 2CO} 3][BF 4] 2 · 0.25H 2O ( 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 · CD 3CN ( 14) and cis-[Ni{(mim) 2CO} 2(OH 2) 2]Br 2 · 3CD 3CN ( 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.