Unusual Cationic Trinuclear Nickel Clusters Incorporating Oxazolines or <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-Tetramethylethylene-1,2-diamine: Applications in Olefin Polymerization

The synthesis and characterization of two rare examples of the nickel(II)-containing trinuclear clusters of the general formula μ<sub>3</sub>-halido-μ<sub>3</sub>-hydroxotris(μ-halido)tris(L) trinickel(II) halide [halide = Cl (<b>2</b>), Br (<b>3</b>); L = 4,4-dimethyl-2-(<i>o</i>-anilinyl)-2-oxazoline] are described. These materials are compared and contrasted to the “parent” chloride salt (<b>1</b>) of this series (L = <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-tetramethylethylene-1,2-diamine and halide = Cl) and its congeners; <b>2</b> and <b>3</b> represent the first oxazoline-containing clusters of this structural class. Both <b>1</b> and <b>2</b> are shown to be active catalysts for the polymerization of olefins (styrene, methyl methacrylate, etc.) using a stoichiometric equivalent of methylaluminoxane as the copromoter, a situation that gives good yields of syndiotactic rich polymers. Density functional theory (B3LYP/6-31G*/LANL2DZ) is employed to hypothesize the likely origin of the activity demonstrated by these compounds.