Five half-sandwich rare earth catalysts Cp'Ln(CH2C6H4NMe2-o)2(1:Cp'=C5Me4SiMe3

Ln=Sc;2:Cp'=C9H7

Ln=Sc;3:Cp'=C5H5

Ln=Sc;4:Cp'=C5H5

Ln=Lu;5:Cp'=C5H5

Ln=Y) were synthesized for homo(co)polymerization of isoprene and styrene activated with [Ph3C]B(C6F5)4] in toluene.The isoprene and styrene polymerization activity

stereoselectivity

molecular weight and molecular weight distribution were studied with these catalysts.The C5H5-ligated scandium complex 3 displayed high activity and cis-1

4-selectivity toward isoprene homopolymerization

and moderate activity and atactic selectivity for the styrene homopolymerization simultaneously.By use of this scandium catalyst

the copolymerization of styrene with isoprene was achieved to afford a family of copolymers with high cis-1

4-isoprene content

controlled molecular weight (Mn=3.5104~8.3104) and narrow molecular weight distribution (Mw/Mn=1.71~1.94).The copolymerization activity reach up to 105 g of polymer (mol of Sc)-1 h-1.The styrene/isoprene copolymers were multi-block copolymers with atactic polystyrene blocks

high cis-1

4-isoprene units (91%).The copolymer composition and molecular weight could be easily controlled by changing the feeding ratio of styrene

isoprene and catalyst.