Half-Sandwich Rare-Earth metal complexes bearing 4,5,6,7-Tetrahydroindenyl 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 [Ph 3 C][B(C 6 F 5 ) 4 ], the THI-ligated scandium complexes exhibited high catalytic activity for highly syndiotactic polymerization of styrene (>99% rrrr ). THI 3Me -Sc /[Ph 3 C][B(C 6 F 5 ) 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 ( 1 H and 13 C) spectra. The huge difference in reactivity ratios betewen styrene and isoprene/butadiene ( r IP / r St  = 31.1 and r BD / r St  = 173.6) revealed in kinetics investigation further proved the predominantly block structure of resultant copolymers.