Affiliation:
1. College of Chemistry, Zhengzhou University, Zhengzhou 450001, China
Abstract
A family of pyridine–oxazoline-ligated cobalt complexes L2CoCl2 3a–h were synthesized and characterized. Determined via single-crystal X-ray diffraction, complexes 3a and 3d, ligated by two ligands, displayed a distorted tetrahedral coordination of a cobalt center. The X-ray structure indicated the pyridine–oxazoline ligands acted as unusual mono-dentate ligands by coordinating only to Noxazoline. Upon activation with AlEt2Cl (diethylaluminum chloride), these cobalt complexes all exhibited high catalytic activity (up to 2.5 × 106 g·molCo−1·h−1), affording cis-1,4-co-3,4-polyisoprene with molecular weights of 4.4–176 kg mol−1 and a narrow Ð of 1.79–3.42, suggesting a single-site nature of the active sites. The structure of cobalt catalysts and reaction parameters, especially co-catalysts and the reaction temperature, all have significant influence on the polymerization activity but not on the microstructure of polyisoprene.
Funder
National Natural Science Foundation of China
Natural Science Foundation of Henan Province
China Postdoctoral Science Foundation
Reference46 articles.
1. Highly 3,4-Selective Polymerization of Isoprene with NPN Ligand Stabilized Rare-Earth Metal Bis(alkyl)s. Structures and Performances;Li;Organometallics,2009
2. Highly Cis-1,4 Selective Polymerization of Isoprene Promoted by α-Diimine Cobalt(II) Chlorides;Wang;J. Polym. Sci. Part A Polym. Chem.,2016
3. Polymerization of Isoprene Promoted by Aminophosphine(ory)-Fused Bipyridine Cobalt Complexes: Precise Control of Molecular Weight and Cis-1,4-alt-3,4 Sequence;Zhao;Inorg. Chem.,2018
4. Dienes polymerization: Where we are and what lies ahead;Ricci;Macromolecules,2021
5. Well-defined transition metal complexes with phosphorus and nitrogen ligands for 1,3-dienes polymerization;Ricci;Coord. Chem. Rev.,2010