Small bite-angle 2-phosphinophosphinine ligands enable rhodium-catalysed hydroboration of carbonyls.

Two Rh complexes of the 2-phosphinophosphinine ligand 2-PPh2-3-Me-6-SiMe3-C5H2P (1) were prepared: dinuclear trans-[{Rh(CO)(Cl)(μ-1)}2] (2) and chelating [Rh(1)(COD)][B(ArF)4] (3). Despite the widespread use of Rh catalysts for the hydroboration of alkenes, 3 is reported to be the first Rh catalyst for ketone and ketimine hydroboration, with high activity observed at 0.1 mol% loading.