Organometallic Synthesis of Bimetallic Cobalt‐Rhodium Nanoparticles in Supported Ionic Liquid Phases (CoxRh100−x@SILP) as Catalysts for the Selective Hydrogenation of Multifunctional Aromatic Substrates

The synthesis, characterization, and catalytic properties of bimetallic cobalt‐rhodium nanoparticles of defined Co:Rh ratios immobilized in an imidazolium‐based supported ionic liquid phase (CoxRh100−x@SILP) are described. Following an organometallic approach, precise control of the Co:Rh ratios is accomplished. Electron microscopy and X‐ray absorption spectroscopy confirm the formation of small, well‐dispersed, and homogeneously alloyed zero‐valent bimetallic nanoparticles in all investigated materials. Benzylideneacetone and various bicyclic heteroaromatics are used as chemical probes to investigate the hydrogenation performances of the CoxRh100−x@SILP materials. The Co:Rh ratio of the nanoparticles is found to have a critical influence on observed activity and selectivity, with clear synergistic effects arising from the combination of the noble metal and its 3d congener. In particular, the ability of CoxRh100−x@SILP catalysts to hydrogenate 6‐membered aromatic rings is found to experience a remarkable sharp switch in a narrow composition range between Co25Rh75 (full ring hydrogenation) and Co30Rh70 (no ring hydrogenation). Bimetallic cobalt‐rhodium nanoparticles of tunable compositions are prepared on an imidazolium‐based supported ionic liquid phase (SILP) using an organometallic approach. The resulting CoxRh100−x@SILP materials are fully characterized and applied to the catalytic hydrogenation of multifunctional aromatic substrates. In particular, benzylidenacetone and bicyclic heteroaromatics serve as chemical probes to study the influence of the Co:Rh metal ratio on activity and selectivity.