Hetero-bimetallic Complexes of Titanatranes with Aluminum Alkyls: Synthesis, Structural Analysis, and Their Use in Catalysis for Ethylene Polymerization
journal contribution
posted on 2010-08-23, 00:00 authored by Prabhuodeyara M. Gurubasavaraj, Kotohiro NomuraHetero-bimetallic Ti−Al complexes containing tris(aryloxo)amine ligands of type [TiR′{(μ<sub>2</sub>-O-2,4-R<sub>2</sub>C<sub>6</sub>H<sub>2</sub>-6-CH<sub>2</sub>)(O-2,4-R<sub>2</sub>C<sub>6</sub>H<sub>2</sub>-6-CH<sub>2</sub>)<sub>2</sub>N}][R′<sub>2</sub>Al(μ<sub>2</sub>-O<sup><i>i</i></sup>Pr)] [<b>3a</b>,<b>b</b> and <b>4a</b>; R = Me (<b>3</b>), <sup><i>t</i></sup>Bu (<b>4</b>); R′ = Me (<b>a</b>), Et (<b>b</b>)] have been prepared by reacting Ti(O<sup><i>i</i></sup>Pr)[(O-2,4-R<sub>2</sub>C<sub>6</sub>H<sub>2</sub>-6-CH<sub>2</sub>)<sub>3</sub>N] [R = Me (<b>1</b>), <sup><i>t</i></sup>Bu (<b>2</b>)] with 1.0 equiv of AlR′<sub>3</sub> in toluene. Crystallographic analyses of <b>3a</b>,<b>b</b> and <b>4a</b> reveal that these complexes have a distorted octahedral geometry around Ti and a distorted tetrahedral geometry around Al. Complexes <b>3a</b>,<b>b</b> and <b>4a</b> exhibited moderate catalytic activities for ethylene polymerization in toluene in the presence of methylaluminoxane (MAO) at 80−120 °C, and <b>4a</b> showed higher activity than <b>3a</b>,<b>b</b>. The <i>tert</i>-butyl analogue (<b>4a</b>) itself polymerizes ethylene without cocatalysts to afford high molecular weight polymer with a uniform distribution, clearly suggesting a hypothesis that cleavage of Ti−O bonds would generate the catalytically active cationic species in this catalysis.
