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

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-butyliminoor 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{[mu-eta(5):eta(1):eta(1)-2-(2,6-iPr(2)C(6)H(3)NCH(2))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)]/AliBu(3) 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 numberaverage molecular weights and narrow to moderate molecular weight distributions.