Scandium-Catalyzed Regio- and Stereospecific cis-1,4-Polymerization of 1,3-Cyclohexadiene and Copolymerization with Ethylene

In the presence of an activator such as [Ph 3 C][B(C 6 F 5 ) 4 ] or [PhMe 2 NH][B(C 6 F 5 ) 4 ], the half-sandwich scandium dialkyl complexes Cp′Sc(CH 2 SiMe 3 ) 2 (THF) (Cp′ = C 5 Me 4 SiMe 3 ( 1 ), C 5 Me 5 ( 2 ), C 5 H 3 (SiMe 3 ) 2 ( 3 )) showed excellent regio- and stereoselectivity for the polymerization of 1,3-cyclohexadiene (CHD) and its copolymerization with ethylene. The homopolymerization of CHD afforded soluble crystalline cis -1,4-linked poly(CHD)s with very high stereoselectivity (tacticity up to 99 mol %). The copolymerization of CHD with ethylene gave the corresponding copolymers with a wide range of CHD contents (10−67 mol %) in a regio- and stereospecific 1,4- cis fashion.