Highly trans-1,4 selective (co-)polymerization of butadiene and isoprene with quinolyl anilido rare earth metal bis(alkyl) precursors

Abstract

The N-R-quinolinyl-8-amino ligands HL^1–3 (R = 2,6-ⁱPr₂C₆H₃ (HL¹), 2,6-Et₂C₆H₃ (HL²), 2,6-Me₂C₆H₃ (HL³)) have been prepared, which reacted readily with one equiv. of rare earth metal tris(alkyl)s to afford the corresponding bis(alkyl) complexes L¹Y(CH₂SiMe₃)₂(THF) (1) and L^1–3Lu(CH₂SiMe₃)₂(THF) (2–4) viaalkane elimination. Contrastingly, treatment of the in situ generated neodymium tri(alkyl)s with HL¹ afforded a mono(alkyl) neodymium complex (5). Complexes 1, 2 and 5 in combination with aluminium alkyls and organoborates established homogenous ternary systems that exhibited versatile catalytic activities and trans-1,4 selectivities for the polymerization of butadiene, depending on the types of aluminium alkyl, organoborate and rare earth metal used. Furthermore, the trans-1,4 selective copolymerization of butadiene and isoprene was achieved by using the ternary system of 1/AlMe₃/[Ph₃C][B(C₆F₅)₄]. Both the kinetics of copolymerization and the thermal behavior of the copolymers were investigated.