A Robust Synthesis of Co₂P and Ni₂P Nanocatalysts from Hexaethylaminophosphine and Phosphine-Enhanced Phenylacetylene Hydrogenation

Metal-rich phases of general formula M₂P have demonstrated interesting catalytic activity, e.g., for hydrogen evolution reaction and for hydrogenations in colloidal suspension. The production of well-crystallized nanoparticles of the M₂P phase from commercial precursors on a large enough scale is not trivial as the existing routes generally require fairly high reaction temperatures and a large excess of the phosphorus source. Here, we selected a commercial aminophosphine, P(NEt₂)₃, as the phosphorus precursor (3 equiv or less) to develop a robust synthesis from CoCl₂ (respectively NiCl₂) that provided crystalline Co₂P (respectively Ni₂P) nanoparticles with high yields on a 9 mmol scale. Moreover, modification of the M₂P nanoparticles via the addition of a molecular Lewis base is a promising route to trigger catalytic activity of the colloidal suspension at a lower temperature. For the hydrogenation of phenylacetylene catalyzed by Co₂P and Ni₂P nanoparticles, we showed that catalytic amounts of adequate phosphines, such as P^<i>n</i>Bu₃ and also, in some instances, oleylamine, triggered a full conversion at lower temperatures than with the nanoparticles alone. We delineated the most efficient phosphines in the case of a Ni₂P catalyst, using a stereoelectronic map of 13 phosphines.