Reduction of Borazines Mediated by Low-Valent Chromium Species

This communication demonstrates the successful reduction of a model for spent AB fuels, Me6B3N3, mediated by a low-valent chromium source. Of particular note, an alkyl borazine was activated by coordination to a {Cr(CO)3} fragment, which facilitated methyl and hydride transfer to the borazine ring, thus establishing a metalmediated reduction pathway. Protonation released a proposed diene fragment that was subsequently trapped by two DOAcF addition reactions across the remaining B=N bonds. The disclosed reactions represent the first well-defined examples of metal-mediated reduction of an alkyl borazine, which, because of its similarity to the products of AB dehydrogenation, provides support to a potentially new B-N regeneration strategy. These reactions are of interest for further studies that target metal-mediated hydrogenation pathways of B=N fragments because metal hydrides are readily generated by hydrogenation and/or protonation of reduced metal complexes. Accordingly, investigations into reductive reactivity with alternative reductants and proton donors are underway, as well as efforts that employ a similar approach to reduce H6B 3N3 and polyborazylene. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.