Scandium half-metallocene-catalyzed syndiospecific styrene polymerization and styrene-ethylene copolymerization: unprecedented incorporation of syndiotactic styrene-styrene sequences in styrene-ethylene copolymers.

On treatment with 1 equiv of [Ph3C][B(C6F5)4], the scandium half-sandwich bis(alkyl) complex (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) showed extremely high activity (up to 1.36 x 104 kg of sPS/(mol Sc.h)) and syndiospecificity (rrrr > 99%) for the polymerization of styrene at room temperature in toluene. More remarkably, this catalyst system could also effect the syndiospecific copolymerization of styrene with ethylene to yield styrene-ethylene copolymers having syndiotactic styrene-styrene sequences. The styrene content in the copolymers could be easily controlled by changing the styrene feed and could reach higher than 80 mol %. This is the first example of formation of such types of styrene-ethylene copolymers, which are expected to show novel properties.