Novel bis(benzoin) titanium catalyst for homo- and copolymerization of norbornene with ethylene: Synthesis, characterization and catalytic properties

A novel titanium(IV) dimeric complex [(OC(Ph)HC(Ph)O)TiCl(μ-OCH(Ph)C(Ph)(n-Bu)O)]2 (1) was synthesized and characterized, and its catalytic behaviors toward homo- and copolymerization of ethylene (E) and norbornene (NB) were also investigated. X-ray diffraction analysis of single crystal structure revealed that the titanium complex features a binuclear and six-coordinate, pseudo-octahedral geometry around titanium metal center with oxo-bridge in the solid state. Activated with methylalumoxane (MAO), the titanium complex exhibited good activities for the homopolymerizations of ethylene and norbornene with long lifetime and produced high-molecular weight linear PE and vinyl-type PNB, respectively. E–NB copolymers with high-molecular weight and high NB incorporation content could be also obtained by this catalyst. The incorporation of NB in the E–NB copolymers could be controlled by varying monomer ratio and reaction temperature. 13C NMR analyses showed that the microstructures of the E–NB copolymers are predominantly alternated and isolated NB units, but the dyad and triad sequences of NB unit could be detected in the copolymers with high NB incorporation. The monomer reactivity ratios of the copolymerization were measured to be rE = 6.0, rN = 0.05 at 30 °C.