Synthesis, characterization and 1,3-butadiene polymerization behaviors of three ONO, ONN, and NNN tridentate Co(II) complexes

• All three CoCl2 complexes performed high activities towards butadiene polymerization.
• Addition of PPh3 or PO(OPh)3 cause distinctly different polymerization behaviors.
• ONO, ONN Co(II) complexes displayed obvious chain transfer towards ZnEt2.

Three kinds of ONO (a), ONN (b), and NNN (c) tridentate Co(II) complexes were synthesized and thoroughly characterized. Determined by single crystal X-ray analysis, the solid structures of b and c displayed distorted trigonal bipyramidal and square pyramidal geometries around the metal centre, respectively. In combination with methylaluminoxane (MAO), all three complexes exhibited high catalytic activities towards 1,3-butadiene polymerization, affording polymers with predominant cis-1,4-contents. With addition of PPh3 into the polymerization system, polybutadienes having predominant 1,2-contents were obtained, while the addition of PO(OPh)3 showed little influence on the microstructure of the polymer. In the investigation of chain transfer polymerization of 1,3-butadiene at the presence of ZnEt2, for complexes a and b, monotonous decreasing in molecular weight along with and an increasing of cis-1,4-content were obtained with an increasing molar ratio of Zn/Co, for complex c, however, unconspicuous changes was observed.

Three kinds of CoCl2-based complexes had been synthesized and all of them performed high activity and high cis-1,4-selectivity towards 1,3-butadiene polymerization. Addition PO(OPh)3 showed no influence to the microstructure of the resulting polybutadiene, albeit addition of PPh3 resulted in 1,2-enriched structure. ONO, ONN CoCl2 complexes displayed obvious chain transfer towards ZnEt2, monotonous decreasing in molecular weight along with and an increasing of cis-1,4-content were observed.Figure optionsDownload as PowerPoint slide