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05:48
Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes
Published on: November 21, 2017
Controlled Amine-Borane Dehydropolymerization Enabled by Mechanistic Insight Using the Ir(tBu-POCOP)H2 Catalyst
Chloe M Van Beek1, M Arif Sajjad2, Joe C Goodall1
1Department of Chemistry, University of York, Heslington, York YO10 5DD, U.K.
Journal of the American Chemical Society
|July 7, 2026
Summary
This study details the catalytic dehydropolymerization of H3B·NMeH2 to N-methyl polyaminoborane (Me-PAB) using an iridium precatalyst. Understanding catalyst speciation and reaction kinetics enables controlled Me-PAB synthesis for preceramic applications.
Area of Science:
- Organometallic Chemistry
- Polymer Chemistry
- Materials Science
Background:
- N-methyl polyaminoborane (Me-PAB) is a promising preceramic polymer for hexagonal boron nitride (h-BN) synthesis.
- Controlled polymerization and understanding reaction mechanisms are crucial for scalable Me-PAB production.
- Iridium-catalyzed reactions offer potential for selective polymer synthesis.
Purpose of the Study:
- To investigate the catalytic dehydropolymerization of H3B·NMeH2 to Me-PAB using an Ir(tBu-POCOP)H2 precatalyst.
- To elucidate the reaction mechanism, kinetics, and catalyst speciation during polymerization.
- To establish a framework for controlling Me-PAB molecular weight and enabling scalable synthesis.
Main Methods:
- Detailed kinetic and mechanistic studies of the dehydropolymerization reaction.
- Operando catalyst speciation monitoring using FlowNMR.
- Numerical and computational (DFT) modeling to support mechanistic proposals.
- Exploration of temperature variation and amine additives for molecular weight control.
Main Results:
- Identified key iridium intermediates, Ir(tBu-POCOP)(H)(BH4) and Ir(tBu-POCOP)H4, involved in catalysis.
- Established a mechanism involving concerted B-H/N-H activation for monomer formation.
- Demonstrated control over Me-PAB molecular weights (35,000-191,200 g·mol⁻¹) through optimized conditions.
- Achieved multigram scale synthesis (16 g) with low catalyst loading (21 ppm) and water/air tolerance.
Conclusions:
- The study provides a comprehensive understanding of the Ir-catalyzed dehydropolymerization of H3B·NMeH2.
- Optimized conditions allow for controlled synthesis of Me-PAB with tunable molecular weights.
- Developed system is scalable and robust, promoting Me-PAB as a viable preceramic precursor for h-BN.
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