Living Isospecific Styrene Polymerization by Chiral Benzyl Titanium Complexes That Contain a Tetradentate [OSSO]-Type Bis(phenolato) Ligand

摘要: Dibenzyl complexes [Ti(OC6H2-R1-6-R2-4)2{S(CH2)2S}(CH2Ph)2] (2a−c; R1 = tBu, R2 Me, a; R1, b; H, c) with a tetradentate dianionic [OSSO]-type ligand were synthesized from the corresponding titanium dichloro [Ti(OC6H2-R1-6-R2-4)2{S(CH2)2S}Cl2] and benzylmagnesium chloride in toluene. NMR spectroscopic monitoring of reaction dibenzyl complex 2b B(C6F5)3 bromobenzene indicates formation thermally sensitive benzyl cation [Ti(OC6H2-tBu2-4,6)2{S(CH2)2S}(CH2Ph)]+. 1H spectra at −30 °C show two C1-symmetric diastereomers 55:45 ratio, suggesting slow epimerization on time scale this temperature. The 2c, which does not bear bulky ortho-substituents, was found to be fluxional unstable solution. Related 1,5-dithiapentanediyl-linked [Ti(OC6H2-tBu-6-R-4)2{S(CH2)3S}(CH2Ph)2] (4a,b; R b) an analogous manner also shown highly fluxional...