Synthesis, characterization and 1,3-butadiene polymerization studies of cobalt dichloride complexes bearing pyridine bisoxazoline ligands

• DOI: 10.1016/j.polymer.2015.01.006
• Publication Date: 2015-01-08T16:37:17Z
• Authors: Jun Guo; Baolin Wang; Jifu Bi; Chunyu Zhang; Hexin Zhang; Chenxi Bai; Yanming Hu; Xuequan Zhang
• Keywords: Octahedral molecular geometry

series of ion-pair cobalt contlexes bearing pyridine bisoxazoline ligands were successfully synthesized and characterized by IR spectroscopy and elemental analysis. Determined by X-ray crystallographic analysis, complexes 4a, 4b, 4e, and 4f existed as ion pairs comprised of [CoL2](2+) and [CoCl4](2-). In the complex, the cobalt atom was coordinated by six nitrogen atoms from two ligands, and its coordination geometry at the cobalt center of [CoL2](2+) can be described as distorted octahedron. In combination with ethylaluminum sesquichloride, these cobalt complexes displayed high catalytic activity and cis-1,4-selectivity towards 1,3-butadiene polymerization. The selectivity of the catalytic system can be tuned to predominantly 1,2-fashion via addition of PPh3. The effects of reaction parameters and the ligand environment on the polymerization were also investigated. (C) 2015 Elsevier Ltd. All rights reserved.