Issue 4, 2013

Revealing the P–B coupling event in the rhodium catalysed dehydrocoupling of phosphine–boranes H3B·PR2H (R = tBu, Ph)

Abstract

We demonstrate that [Rh(η6-FC6H5)(Ph2PCH2CH2CH2PPh2)][BArF4] is a competent catalyst for the dehydrocoupling of H3B·PR2H to give H3B·PR2BH2·PR2H (R = Ph, tBu). The isolation of intermediates (R = tBu, Ph) and kinetic/isotopic labelling experiments (for R = Ph) point to a mechanism, for R = Ph, in which the rate-limiting process for dehydrocoupling involves B–H activation, while the turnover limiting process for catalysis involves the substitution of the oligomeric product at the metal, which forms a strong chelate complex with a Rh(III) centre, by H3B·PPh2H. When R = tBu no chelate product complex forms, and it is speculated that the dehydrocoupling process now becomes turnover limiting. These observations provide, for the first time we believe, data on the P–B bond forming events that are central to the dehydrocoupling and dehydropolymerisation of phosphine–boranes.

Graphical abstract: Revealing the P–B coupling event in the rhodium catalysed dehydrocoupling of phosphine–boranes H3B·PR2H (R = tBu, Ph)

Supplementary files

Article information

Article type
Edge Article
Submitted
14 Jan 2013
Accepted
18 Feb 2013
First published
19 Feb 2013

Chem. Sci., 2013,4, 1881-1888

Revealing the P–B coupling event in the rhodium catalysed dehydrocoupling of phosphine–boranes H3B·PR2H (R = tBu, Ph)

M. A. Huertos and A. S. Weller, Chem. Sci., 2013, 4, 1881 DOI: 10.1039/C3SC50122A

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