Polymerization of methyl methacrylate catalyzed by nickel complexes with hydroxyindanone-imine ligands

Abstract

A series of new hydroxyindanone-imine ligands [PhNCC₂H₃(CH₃)C₆H₂(CH₃)OH] (HL₁11) and [ArNCC₂H₃(CH₃)C₆H₂(R)OH] (Ar = 2,6-i-Pr₂C₆H₃, R = Me (HL₂22), R = H (HL₃33), and R = Cl (HL₄44)) were synthesized and characterized. Reactions of hydroxyindanone-imines with Ni(OAc)₂·4H₂O result in the formation of the trinuclear hexa(indanone-iminato)tri(nickel(II)) complex Ni₃[PhNCC₂H₃(CH₃)C₆H₂(CH₃)O]₆ (1) and the mononuclear bis(indanone-iminato)nickel(II) complexes Ni[ArNCC₂H₃(CH₃)C₆H₂(R)O]₂ (Ar = 2,6-i-Pr₂C₆H₃, R = Me (2), R = H (3), and R = Cl (4)). All nickel complexes were characterized by their IR, NMR spectra and elemental analyses. In addition, X-ray structure analyses were performed for complexes 1 and 2. After being activated with methylaluminoxane (MAO), these nickel(II) complexes can be used as catalysts for the polymerization of methyl methacrylate (MMA) to produce syndiotactic-rich PMMA. Catalytic activities and the degree of syndiotacticity of PMMA have been investigated for various reaction conditions.