A bulky polymer-supported frustrated Lewis pair: Dihydrogen cleavage with poly(methylenephosphine)-tris(pentafluorophenyl)borane

• Demonstrated H 2 activation by poly(methylenephosphine)s and B(C 6 F 5 ) 3 . • Characterization aided by molecular model compounds. • Hydrogen-loaded polymer can be utilized to reduce imines. Polymeric frustrated Lewis pairs (FLPs) have recently attracted attention due to their potential to enhance recyclability or catalytic activity when compared to their monomeric counterparts. In this work, we explore Lewis basic inorganic polymers, namely poly(methylenephosphine)s ( PMP s), as novel platforms for polymeric FLPs. To aid in characterization of the polymers, molecular model FLPs, MesP(R)–CHPh 2 [R = Me ( 1a ), n-Bu ( 1b ), CHPh 2 ( 1c )] and B(C 6 F 5 ) 3 , were employed. Each successfully activated H 2 to afford [MesPH(R)–CHPh 2 ][HB(C 6 F 5 ) 3 ] ( 2a-c ). Following a similar strategy, PMP ( M n = 12,850 Da, Đ = 1.08), produced by the living anionic polymerization of MesP=CPh 2 , was shown to effectively cleave H 2 . Specifically, approximately 50 % of the phosphine moieties in PMP were converted to the corresponding phosphonium borate ionomer. This hydrogen-loaded polymer successfully reduced imine, PhC(H)=N( t- Bu), thereby reforming PMP and demonstrating proof-of-concept for PMP s as polymeric Lewis bases in FLP chemistry.