(125e) Tailoring Catalyst Selectivity for 1,3-Butadiene Hydrogenation: Effects of Metal Nuclearity and Ligands

Supported bimetallic catalysts offer rich design opportunities, because the metals can play complementary roles affecting activity, selectivity, and stability. Understanding the function of bimetallic catalysts is often challenging because the common preparation methods are not precise enough to avoid complex mixtures of monometallic and bimetallic species with various morphologies. To better understand the mode of action of bimetallic catalysts, we investigated the synthesis and performance of a set of catalysts that incorporate multiple types of active sites on supports (e.g., zeolite HY and MgO). The catalytic species, made from organometallic precursors, are site-isolated and essentially molecular, and the nuclearity of these species and the ligands bonded to the metals were varied independently. The data show the influence that one metal exerts over the performance of the other in the presence of various reactive atmospheres, including effects on catalytic selectivity (illustrated by ruthenium/iridium combinations), stability in H₂ (osmium/rhodium combinations), and formation of heterometallic bonds (ruthenium/osmium combinations).