Affiliation:
1. Department of Materials Science and Bioengineering Nagaoka University of Technology Nagaoka Niigata Japan
2. Department of Materials Science and Technology Nagaoka University of Technology Nagaoka Niigata Japan
3. Department of Frontier Materials Chemistry, Graduate School of Science and Technology Hirosaki University Hirosaki Aomori Japan
Abstract
ABSTRACTConstrained geometry complexes (CGCs) are homogeneous olefin polymerization catalysts that have been improved because of their considerably high activity and their copolymerization abilities for ethylene with α‐olefins. The ancillary ligands in CGCs comprise bridged 6π‐electron moieties (e.g., cyclopentadienyl (Cp) and fluorenyl) and amide donors. In this study, we investigated the effect of changing the 6π‐electron moieties to a diphenylmethyl moiety (Ph2C) on the polymerization activity of [Me2Si(Ph2C)(tBuN)]ZrCl2(thf) (thf = tetrahydrofuran). We synthesized [Me2Si(Ph2C)(tBuN)]ZrCl2(thf) and characterized it via 1H nuclear magnetic resonance analysis and single‐crystal X‐ray crystallography. Ethylene polymerization at 2 MPa using a catalyst of the [Me2Si(Ph2C)(tBuN)]ZrCl2(thf) and modified methylaluminoxane (MMAO) as a cocatalyst yielded a linear polyethylene (PE) with a high melting point (124°C–134°C); moreover, the polymerization activity of the catalyst was found to be up to 445 g (PE) mmol (Zr)−1 h−1. The polymerization of styrene using the zirconium complex and MAOs did not proceed, but the polymerization of 1,3‐butadiene produced a small amount of polybutadiene with ~60% cis‐1,4‐structure. These results indicate that non‐Cp‐type CGCs, which can be defined as metal complexes bearing an ancillary ligand in which non‐Cp moieties (benzyl moiety in this study) and an amido group are bridged by an organic linker, can become a new family of homogeneous olefin polymerization catalysts.