Abstract
A series of group 4 metal complexes 1–4 (1 = (t-BuOS)2Ti(O-i-Pr)2; 2 = (t-BuOS)2Zr(O-t-Bu)2; 3 = (t-BuOS)2Hf(O-t-Bu)2; 4 = (CumOS)2Zr(O-t-Bu)2) supported by two phenolate bidentate ligands (t-BuOS–H = 4,6-di-tert-butyl-2-phenylsulfanylphenol and CumOS–H = 4,6-dicumyl-2-phenylsulfanylphenol) were synthesized by the reaction of appropriate metal tetra(alkoxide)s with 2 equiv of the ligands. The X-ray structure of 2 revealed that the two ligands were κ2-chelated to the metal center with two phenoxy groups in trans positions and the two thioether moieties in cis positions. VT NMR analysis revealed a fast inversion of configuration at the metal center. Complexes 1–4 promoted the ring-opening polymerization (ROP) of lactide and e-caprolactone. Complex 4 exhibited the highest activity with a pseudo-first-order rate constant of 0.061 ± 0.003 min–1 at 100 °C, which compares favorably with those reported for the most active group 4 complexes. Polymerizations were well-controlled, giving predictable molecular weight...
Published Version
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