Abstract
Cobalt complexes (Co1–Co6) bis-chelated by phenoxy (4,6-di-tert-butyl-2-phenol, naphthalen-2-ol)-imine ligands containing pendant hard oxygen (Co1 and Co4), soft sulfur (Co2 and Co5), or phosphine donors (Co3 and Co6) are reported for dual catalysis of selective polymerization for biosourced myrcene and methyl methacrylate (MMA). X-ray analysis reveals that the complexes features a distorted octahedral coordination of the cobalt center binding with phenolate oxygen, imine nitrogen, and pendant donor (P for Co3 and S for Co5). Activated by MMAO or AliBu3, all precursors are able to not only convert myrcene to cis-1,4-polymyrence but also polymerize MMA resulting in poly(methyl methacrylate) (PMMA) with moderate syndiotacticity. The introduction of pendant donor concurrently improves activity and stability particularly at 60–80 °C for polymerizations of both monomers. The enhanced activity and selectivity observed in myrcene cis-1,4 polymerization promoted by the sulfur and oxygen containing catalysts may relate to the weak Co–X (X = O, S) interaction, facilitating myrcene coordination. However, the donor effect on MMA polymerization activity is reversed, with phosphine donated catalyst demonstrating remarkably enhanced activity. This study represents the first example of cobalt catalyzed polymerization of both polar and nonpolar functions via possible mechanisms differentiated by pendant donor and also may provide valuable insights into their essential role in mediating the polymerization process.
Published Version
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