Borane/silane frustrated Lewis pairs for polymerization of β-substituted Michael acceptors.

Abstract Frustrated Lewis pairs (FLPs) of Lewis acid (LA) B(C 6 F 5) 3 and Lewis base hydrosilane [SiH] have been utilized to promote controlled polymerization of a challenging β -substituted Michael acceptor, methyl crotonate (MC), devoid of chain transfer side reactions. Mechanistic studies show that chain initiation involves LA-catalyzed 1,4-hydrosilylation of MC with [SiH] via FLP-type activation, generating a silyl ketene acetal nucleophile that participates in chain propagation via classic LA activation of monomer and a bimolecular conjugate addition mechanism. The role of the LA is conflicting in the two different catalytic cycles: the FLP activation in chain initiation requires LA-substrate (monomer) dissociation (or weak interaction) while the classic LA activation in chain propagation demands LA-monomer association (or strong interaction). Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]