Catalytic performance of tridentate bidentate Co(ii) complexes supported by Schiff base ligands in vinyl addition polymerization of norbornene.

A series of Co(ii) complexes supported by Schiff base ligands, L-L, where L, L, and L are ()-3-methoxy--(quinolin-2-ylmethylene)propan-1-amine, ()- , -dimethyl- -(pyridin-2-ylmethylene)ethane-1,2-diamine, and ()- , -dimethyl- -(thiophen-2-ylmethylene)ethane-1,2-diamine, respectively, were designed and synthesized. Structural studies revealed a distorted trigonal bipyramidal geometry for [LCoCl] and a distorted tetrahedral geometry for [LCoCl]. After activation with modified methyl aluminoxane (MMAO), all the Co(ii) complexes catalyzed the polymerization of norbornene (NB) to yield vinyl-type polynorbornenes (PNBs) with activities of up to 4.69 × 10 g mol Co h at 25 °C. High-molecular-weight ( of up to 1.71 × 10 g mol) soluble PNBs with moderate molecular-weight distributions (MWD) were obtained. The activity of the Co(ii)/MMAO catalytic system is influenced by the steric hindrance and electronic properties of the ligands.