Catalytic performance of tridentate versus bidentate Co(ii) complexes supported by Schiff base ligands in vinyl addition polymerization of norbornene. Issue 55 (21st December 2022) - Kim, Kyeonghun
Abstract : A series of Co(ii ) complexes supported by Schiff base ligands were designed and synthesized. A distorted tetrahedral geometry of [LC CoCl2 ] showed excellent catalytic activity at 25 °C (99% yield). Abstract : A series of Co(ii ) complexes supported by Schiff base ligands, LA –LC, where LA, LB, and LC are ( E )-3-methoxy- N -(quinolin-2-ylmethylene)propan-1-amine, ( E )- N 1, N 1 -dimethyl- N 2 -(pyridin-2-ylmethylene)ethane-1, 2-diamine, and ( E )- N 1, N 1 -dimethyl- N 2 -(thiophen-2-ylmethylene)ethane-1, 2-diamine, respectively, were designed and synthesized. Structural studies revealed a distorted trigonal bipyramidal geometry for [LB CoCl2 ] and a distorted tetrahedral geometry for [LC CoCl2 ] . 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 4 gPNB mol Co −1 h −1 at 25 °C. High-molecular-weight ( M n of up to 1.71 × 10 5 g mol −1 ) 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.