The Dehydropolymerization of H3B•NMeH2 to form Polyaminoboranes using [Rh(Xantphos–alkyl)] Catalysts.

Gemma M. Adams, Annie Louise Colebatch, Joseph T. Skornia, Alasdair I. Mckay, Heather C. Johnson, Guy C. Lloyd-jones, Stuart A. Macgregor, Nicholas A. Beattie, Andrew S. Weller

Research output: Contribution to journalArticlepeer-review


A systematic study of the catalyst structure and overall charge for the dehydropolymerization of H3B·NMeH2 to form N-methyl polyaminoborane is reported using catalysts based upon neutral and cationic {Rh(Xantphos–R}}
fragments, in which PR2 groups are selected from Et, iPr and tBu. The most efficient systems are based upon {Rh(Xantphos–iPr}}, i.e. [Rh(k3–P,O,P–Xantphos–iPr)(H)2(h1–H3B·NMe3)][BArF4], 6, and Rh(k3–P,O,P–Xantphos–iPr)H,
11. While H2 evolution kinetics show both are fast catalysts (ToF ~ 1500 hr–1), and polymer growth kinetics for dehydropolymerization suggest a classical chain growth process for both, neutral 11 (Mn = 28,000 g mol–1, Ð = 1.9) promotes
significantly higher degrees of polymerization than cationic 6 (Mn = 9,000 g mol–1, Ð = 2.9). For 6 isotopic labelling studies suggest a rate determining NH activation, while speciation studies, coupled with DFT calculations, show the formation of a dimetalloborylene [{Rh(k3–P,O,P–Xantphos–iPr)}2B]+ as the, likely dormant, end product of catalysis. A dual mechanism is proposed for dehydropolymerization, in which neutral hydrides (formed by hydride transfer in cationic 6 to form a boronium co–product) are the active catalysts for dehydrogenation to form aminoborane. Contemporaneous chain–growth polymer propagation occurs on a separate metal center via head-to-tail end chain B–N bond formation of the aminoborane monomer, templated by an aminoborohydride–containing catalyst.
Original languageEnglish
JournalJournal of the American Chemical Society
Early online date29 Dec 2017
Publication statusE-pub ahead of print - 29 Dec 2017


Dive into the research topics of 'The Dehydropolymerization of H3B•NMeH2 to form Polyaminoboranes using [Rh(Xantphos–alkyl)] Catalysts.'. Together they form a unique fingerprint.

Cite this