cis-1,4-Polymerization of isoprene catalyzed by rare-earth metal amido complexes supported by 2-t-butylimino- or 2-amino-functionalized indolyl ligand

Abstract Aiming at developing highly efficient and more conveniently treated rare-earth metal catalyst systems, the performance of a series of the rare-earth metal amido complexes bearing 2-t-butylimino- or 2-amino-functionalized indolyl ligands as precatalysts toward isoprene polymerization was investigated. Under the activation of borate activator [Ph3C][B(C6F5)4] and AlR3, the monomeric bis(amido) complexes [2-(tBuN = CH)C8H5N]RE[N(SiMe3)2]2 (RE = Er (1), Y (2), Sm (3), Nd (4)) and the dinuclear complex {[µ-η5:η1:η1-2-(2,6-iPr2C6H3NCH2)C8H5N]Nd[N(SiMe3)2]}2 (5) exhibit different catalytic activities and cis-1,4-selectivities for isoprene polymerization depending on cocatalysts of aluminum alkyls, central rare-earth metals and the solvents. Among them, the homogeneous ternary system Nd complex 4 or 5/ [Ph3C][B(C6F5)4]/AliBu3 could very efficiently catalyze polymerization of isoprene under the relatively mild conditions to afford the cis-1,4-polyisoprenes (up to 98.3%) with high number-average molecular weights and narrow to moderate molecular weight distributions.