In Situ Formation of a Sub-Nanometer Iridium Phosphide Catalyst from Supported Organometallic Species

While several metal phosphides have attracted significant attention in the last several years due to their potential use as photocatalytic and hydrotreating catalysts, iridium phosphide has remained largely unexplored. In this work, silica-supported pincer-iridium species are thermolyzed, resulting in deconstruction of the tridentate ligand precursor and formation of a sub-nanometer iridium phosphide phase characterized by ³¹P magic angle spinning nuclear magnetic resonance (³¹P-MAS-NMR), X-ray absorption spectroscopy (XAS), and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The support material was found to play an active role in determining the product of the surface thermolysis, with the silica supported material generating phosphorus rich iridium phosphide nanoparticles. The resulting silica-supported iridium phosphide phase is explored as a thermocatalyst for non-oxidative butane dehydrogenation, achieving high initial reaction rates up to 900 mol_butenes mol_catalyst^-1 hr^-1 and a terminal olefin selectivity of up to 70 %.