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

Abstract

In the presence of an activator such as [Ph3C][B(C6F5)4] or [PhMe2NH][B(C6F5)4], the half-sandwich scandium dialkyl complexes Cp′Sc(CH2SiMe3)2(THF) (Cp′ = C5Me4SiMe3 (1), C5Me5 (2), C5H3(SiMe3)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