Ru_x Pt_y Sn_z cluster-derived nanoparticle catalysts: Spectroscopic investigation into the nature of active multinuclear single sites

Cluster-derived Ru_xPt_ySn_z nanoparticles are active catalysts in the hydrogenation of nitrobenzene. The nature of the active sites has been elucidated by FTIR spectroscopy using CO and NO as probe molecules. A new metal carbonyl cluster precursor, Pt₂Ru₂(SnBu^t₃)₂(CO)₉(μ-H)₂, has been synthesized to obtain a Ru₂Pt₂Sn₂/SiO₂ catalyst, that displayed remarkably high levels of conversion and selectivities compared to other bi-and monometallic analogues. Spectroscopic comparisons with Ru₅PtSn/SiO₂ indicate that both the nature and the stoichiometry of the metals play a key role in modulating the catalytic activities and selectivities. A multinuclear single-site containing Pt centers, which facilitate the hydrogen activation, coupled with a highly reactive Ru site, possibly involved in the nitrobenzene activation, can be hypothesized. The oxophilicity of tin helps with the anchoring of the nanoparticles, aids the dispersion of the other metals, and can play an important role in influencing the selectivity to aniline.