Half-Sandwich Rare-Earth metal complexes bearing 4,5,6,7-Tetrahydroin- denyl ligands for highly Syndiospecific (Co)Polymerization of styrene

As Cp-derived ligands, substituted 4,5,6,7-tetrahydroindene (THI) ligands with tunable steric bulk have been synthesized, and their ligated half-sandwich rare-earth metal complexes were also sucessfully prepared and tested for styrene (co)polymerization. In conjunction with [Ph3C][B(C6F5)4], the THI-ligated scandium com-plexes exhibited high catalytic activity for highly syndiotactic polymerization of styrene (>99% rrrr). THI3Me-Sc/[Ph3C][B(C6F5)4] binary system also promoted the copolymerization of styrene and isoprene/butadiene by both the concurrent addition and sequentical addition of monomers, affording the copolymers with block microstructure as deterimined by NMR (1H and 13C) spectra. The huge difference in reactivity ratios betewen styrene and isoprene/butadiene (rIP / rSt = 31.1 and rBD / rSt = 173.6) revealed in kinetics investigation further proved the predominantly block structure of resultant copolymers.