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Metal-free dehydropolymerisation of phosphine-boranes using cyclic (alkyl)(amino)carbenes as hydrogen acceptors

The divalent carbene carbon centre in cyclic (alkyl)(amino)carbenes (CAACs) is known to exhibit transition-metal-like insertion into E–H σ-bonds (E = H, N, Si, B, P, C, O) with formation of new, strong C–E and C–H bonds. Although subsequent transformations of the products represent an attractive str...

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Detalles Bibliográficos
Autores principales: Oldroyd, Nicola L., Chitnis, Saurabh S., Annibale, Vincent T., Arz, Marius I., Sparkes, Hazel A., Manners, Ian
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Nature Publishing Group UK 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6435733/
https://www.ncbi.nlm.nih.gov/pubmed/30914640
http://dx.doi.org/10.1038/s41467-019-08967-8
Descripción
Sumario:The divalent carbene carbon centre in cyclic (alkyl)(amino)carbenes (CAACs) is known to exhibit transition-metal-like insertion into E–H σ-bonds (E = H, N, Si, B, P, C, O) with formation of new, strong C–E and C–H bonds. Although subsequent transformations of the products represent an attractive strategy for metal-free synthesis, few examples have been reported. Herein we describe the dehydrogenation of phosphine-boranes, RR’PH·BH(3), using a CAAC, which behaves as a stoichiometric hydrogen acceptor to release monomeric phosphinoboranes, [RR’PBH(2)], under mild conditions. The latter species are transient intermediates that either polymerise to the corresponding polyphosphinoboranes, [RR’PBH(2)](n) (R = Ph; R’ = H, Ph or Et), or are trapped in the form of CAAC-phosphinoborane adducts, CAAC·H(2)BPRR’ (R = R’ = tBu; R = R’ = Mes). In contrast to previously established methods such as transition metal-catalysed dehydrocoupling, which only yield P-monosubstituted polymers, [RHPBH(2)](n), the CAAC-mediated route also provides access to P-disubstituted polymers, [RR’PBH(2)](n) (R = Ph; R’ = Ph or Et).