Borohydrido rare earth based coordinative chain transfer copolymerization: A convenient tool for tuning the microstructure of isoprene/styrene copolymers

Abstract

AbstractA series of lanthanum and neodymium borohydrido complexes comprising the trisborohydrides Nd(BH4)3(THF)3 (1a) and La(BH4)3(THF)3 (1b) and the half‐lanthanidocenes Cp*Nd(BH4)2(THF)2 (2a) (Cp* = C5Me5) and Cp*La(BH4)2(THF)2 (2b) has been assessed for the chain transfer copolymerization of isoprene and styrene. A transmetalation process is occurring efficiently with the borohydride complexes in the presence of magnesium dialkyl. The transmetalation is accompanied by (i) a gradual decrease of the 1,4‐trans stereoselectivity of the reaction at the benefit of 3,4‐selectivity and (ii) an increase in the quantity of styrene inserted in the copolymer. This can be at least partially attributed to a magnesium induced co‐oligomerization of isoprene and styrene. By combining dialkylmagnesium and trialkylaluminum, a 1,4‐trans stereospecific reversible coordinative chain transfer copolymerization of isoprene and styrene is observed when the half‐lanthanocene 2b is used as precatalyst. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011