896111-18-5Relevant academic research and scientific papers
Living isospecific styrene polymerization by chiral benzyl titanium complexes that contain a tetradentate [OSSO]-type bis(phenolato) ligand
Beckerle, Klaus,Manivannan, Ramanujachary,Spaniol, Thomas P.,Okuda, Jun
, p. 3019 - 3026 (2006)
Dibenzyl complexes [Ti(OC6H2-R1-6-R 2-4)2{S(CH2)2S}(CH 2Ph)2] (2a-c; R1 = tBu, R 2 = Me, a; R1, R2 = tBu, b; R 1 = H, R2 = Me, c) with a tetradentate dianionic [OSSO]-type ligand were synthesized from the corresponding titanium dichloro complexes [Ti(OC6H2-R1-6-R2-4) 2{S(CH2)2S}Cl2] and benzylmagnesium chloride in toluene. NMR spectroscopic monitoring of the reaction of the dibenzyl complex 2b with B(C6F5)3 in bromobenzene indicates the formation of a thermally sensitive benzyl cation [Ti(OC6H2-tBu2-4,6) 2{S(CH2)2S}(CH2Ph)]+. 1H NMR spectra at -30°C show two C1-symmetric diastereomers in a 55:45 ratio, suggesting slow epimerization on the NMR time scale at this temperature. The benzyl complex 2c, which does not bear bulky ortho-substituents, was found to be fluxional and unstable in solution. Related benzyl complexes of the 1,5-dithiapentanediyl-linked ligand [Ti(OC 6H2-tBu-6-R-4)2{S(CH 2)3S}(CH2Ph)2](4a,b; R = Me, a; R = tBu, b) were synthesized in an analogous manner ' and were also shown to be highly fluxional and unstable in solution, decomposing immediately upon addition of B(C6F5)3. Using the 1,4-dithiabutanediyl-linked dibenzyl complexes and the activators [PhNMe 2H][B(C6F5)4]/AlnOct 3, the living isospecific polymerization of styrene could be achieved for the first time. The resulting isotactic polystyrenes show narrow molecular weight distributions (Mw/Mn n and the monomer conversion was observed.
