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

摘要: A series of titanium dichloro and di(isopropoxy) complexes with a 1,4-dithiabutanediyl-linked bis(4,6-disubstituted phenolato) ligand [Ti(OC6H2-6-R1-4-R2)2{S(CH2)2S}X2] (X = Cl, 2a−i, OiPr, 3a−i; R1 H, Me, iPr, tBu, 2-phenyl-2-propyl; R2 OMe, 2-phenyl-2-propyl) were synthesized by reacting the corresponding linked bis(phenol) (HOC6H2-6-R1-4-R2)2{S(CH2)2S} (1a−i) precursor TiX4. The NMR spectra Ti(OC6H2-6-R1-4-R2)2{S(CH2)2S}Cl2] (2a−d) small ortho substituents iPr are in agreement C2-symmetrical helical structure, but become fluxional at higher temperatures. [Ti(OC6H2-6-R1-4-R2)2{S(CH2)2S}(OiPr)2] (3a−d) solution room temperature due to rapid interconversion between Δ Λ isomers. In contrast, both 2e−i 3e−i bulky tBu 2-phenyl-2-propyl exhibit rigid he...