Amine–Borane Dehydropolymerization Using Rh-Based Precatalysts: Resting State, Chain Control, and Efficient Polymer Synthesis
David E. Ryan, Kori A. Andrea, James J. Race, Timothy M. Boyd, Guy C. Lloyd‐Jones, Andrew S. Weller
Abstract
A detailed study of H3B·NMeH2 dehydropolymerization using the cationic precatalyst [Rh(DPEphos)(H2BNMe3(CH2)2tBu)][BArF4] identifies the resting state as dimeric [Rh(DPEphos)H2]2 and boronium [H2B(NMeH2)2]+ as the chain-control agent. [Rh(DPEphos)H2]2 can be generated in situ from Rh(DPEphos)(benzyl) and catalyzes polyaminoborane formation (H2BNMeH)n [Mn = 15 000 g mol-1]. Closely related Rh(Xantphos)(benzyl) operates at 0.1 mol % to give a higher molecular weight polymer [Mn = 85 000 g mol-1] on the gram scale with low residual [Rh], 81 ppm. This insight offers a mechanistic template for dehydropolymerization.
Topics & Concepts
XantphosCationic polymerizationChemistryAmine gas treatingCatalysisBoraneRhodiumPolymerPolymer chemistryMedicinal chemistryOrganic chemistryPalladiumHydrogen Storage and MaterialsOrganoboron and organosilicon chemistryBoron Compounds in Chemistry