Synthesis of Novel Dinuclear Complexes by Olefin Metathesis and Their Use in Olefin Polymerization

Dinuclear complexes attracted attention as ethylene and olefin polymerization catalysts because they frequently show different catalytic properties than their mononuclear analogues. Most of the known dinculear catalysts are composed of the same transition metal centers. Herein we synthesized novel dinuclear complexes by the olefin metathesis reaction and used them as the catalysts for olefin polymerization. Olefin metathesis of the zirconocenes with alkenyl group affords the dinuclear Zr complexes having a bridging spacer with various lengths. The dinuclear complexes show higher catalytic activity for ethylene polymerization than the corresponding mononuclear complexes. Heterodinuclear complexes containing early and late transition metals were synthesized by facile cross-metathesis reaction. They promote polymerization of ethylene to afford polyethylene with various branched structures depending on the combination of the metal centers. The polymerization mechanism includes formation of ethylene oligomers on the late transition metal center followed by copolymerization of ethylene with those oligomers on early transition metal center.