In Situ Formation of Ru-Pd Alloy Nanocrystals Enables Arene Hydrogenation under Ambient Conditions

Arene hydrogenation constitutes a direct and strategically valuable entry to three-dimensional molecular architectures from abundant aromatic feedstocks. Despite its conceptual simplicity, the intrinsic stability of aromatic systems typically necessitates forcing conditions, i.e., elevated hydrogen pressures and temperatures, which in turn demand specialized infrastructure and constrain broader adoption in synthetic endeavors. Here, we report a simple strategy for generating a highly active, heterogeneous catalyst in situ that enables the efficient hydrogenation of benzene and pyridine derivatives under ambient conditions. Central to this approach is the combination of bench-stable Ru(NH 3 ) 5 (OTf)(OTf) 2 and Pd/C pre-catalysts, which form a catalytically competent and recyclable nanocrystalline Ru-Pd solid solution under the reaction conditions. Comprehensive characterization utilizing microscopic and spectroscopic material analysis techniques is reported, revealing detailed information about the composition of the active catalyst. Further mechanistic investigations and comparative studies with other ruthenium sources underscore the distinctive role of Ru(NH 3 ) 5 (OTf)(OTf) 2 in the catalyst formation process, demonstrating stepwise reductive decomposition of pentaammineruthenium. Collectively, these findings outline a practical approach to arene hydrogenation under ambient conditions while providing important mechanistic insight into the genesis of in situ -formed heterogeneous hydrogenation catalysts.