Jiang, Y; Kang, X; Zhang, Z; Li, S; Cui, D; ,
Coordination polymerization of 1-phenyl-1,3-butadiene (1PB) has been carried out using diiminophosphinato lutetium complexes 1 and 2, pyridyl-methylene-fluorenyl complexes 3 (Sc 3a; Lu 3b; Y 3c) and 4 (Sc 4a; Lu 4b; Y 4c), beta-diketiminato yttrium complex 5, bis(imino)aryl gadolinium complex 6, bis-(ph osphino)carbazolide yttrium complex 7, and bis-(phosphinophenyl)amido yttrium complex 8. Complexes 1, 2, 3a,b, and 4a,b, under the activation of [Ph3C][B(C6F5)(4)] and (AlBu3)-Bu-i, show high activities as well as higher than 96.6% 3,4regioselectivities, of which 1 and 2 are nonstereoselective, giving atactic 3,4-poly(1PB), while 3a,b and 4a,b exhibit distinguished syndioselectivities (>= 95.3% rrrr). However, 3c and 4c are inactive. In addition, complexes 5-7 are also completely inert although they are highly active and cis-1,4-selective for isoprene polymerization. On the contrary, the analogous cis-1,4-selective complex 8 exhibits syndio- (>= 96.1% rrrr) and 3,4-regio- (>99%) selectivity. Hydrogenation of a syndiotactic 3,4-poly(1PB) affords a syndiotactic poly(4-phenyl-1-butene) elastomer with a T-g of 17 degrees C. The cationic cyclization transfers a syndiotactic 3,4-poly(1PB) into a rigid cyclized polyolefin with a T-g as high as 327 degrees C. Density functional theory (DFT) simulations are employed to illustrate the mechanisms for the control of activity and stereoselectivity from thermodynamic and geometric viewpoints.