Alkyne hydrophosphinylation catalyzed by rhodium pyrazolylborate complexes

Despite numerous examples of stoichiometric bond activation reactions using rhodium pyrazolylborate complexes, the use of these complexes in catalytic reactions is still uncommon. We have evaluated the activity of Tp∗Rh(PPh3)2 [Tp∗ = hydrotris(3,5-dimethylpyrazolyl)borate] and Tp∗Rh(cod) (cod = cyclooctadiene) in alkyne hydrophosphinylation relative to a series of known catalysts for this reaction. Both Tp∗Rh(PPh3)2 and Tp∗Rh(cod) are active catalysts for alkyne hydrophosphinylation, although neither is as active as Wilkinson’s catalyst. The ability of Tp∗Rh(PPh3)2 to effect hydrophosphinylation of a series of alkyne substrates with diphenylphosphine oxide is also presented. In addition, we report the crystal structures of the products of the reactions between diphenylphosphine oxide and both [μ-ClRh(cod)]2 and Tp∗Rh(PPh3)2. The former is a possible catalytically relevant intermediate, while the latter is inactive.