A series of cobalt complexes supported by pyridine-oxazoline (Pyox) and quinoline-oxazoline (Quox) were synthesized. Determined by single crystal X-ray crystallography, complexes 6a and 7c adopted distorted octahedron and trigonal bipyramid geometries, respectively, while complex 6b existed as an ion pair comprised of [CoL2]2+ and [CoCl4]2-, in which the cationic and anionic moieties displayed distorted octahedron and tetrahedral geometries, respectively. Upon activation with ethylaluminium sesquichloride (EASC), these cobalt complexes exhibited high catalytic activity and cis-1,4-selectivity toward 1,3-butadiene polymerization. The selectivity of the catalytic system could be switched from cis-1,4 to 1,2-fashion via the addition of PPh3. The effects of ligand environment, polymerization temperature, and [Al]/[Co] ratio on the polymerization were investigated in detail.
Bibliographical noteFunding Information:
The authors appreciate financial support from National Basic Research Program of China , Grant No. 2015CB654700 (2015CB674702), The CAS Hundred Talents Program ( Y220011001 ), the Funds for National Natural Scientific Foundation of China (Nos. 51473156 and 51203147 ) and Jilin Provincial Research Fund for Basic Research , China (No. 20130102007JC ).
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- 1,3-Butadiene polymerization
- Cobalt complex