ONE POT MECHANOCHEMICAL SYNTHESIS OF Ru(PP)(NN)Cl2 COMPLEXES FOR SOLVENT FREE OXIDATION CATALYSIS

Mechanochemistry has emerged as a powerful and sustainable synthetic platform, enabling efficient transformations under solvent free or solvent-minimized conditions. In organometallic synthesis, where large solvent volumes, air sensitivity, and energy- intensive conditions are often required, mechanochemical approaches offer significant advantages in terms of efficiency, sustainability, and operational simplicity. Ruthenium diphosphine–diimine complexes of general formula [Ru(PP)(NN)X2] have attracted continuous interest since the pioneering work of Noyori and co-workers, owing to their prominent role in transfer hydrogenation and reduction processes. Herein, we report for the first time the one-pot mechanochemical route to a series of [Ru(PP)(NN)X2] complexes starting from [Ru(COD)Cl2] or RuCl3. Various diphosphine ligands (dppe, dppp, dppb, dppf, dppbz) were milled in the presence of 2,2′ bipyridine or 1,10-phenanthroline, affording the corresponding Ru(II) complexes in good to excellent yields. A comparative evaluation of green metrics (E-factor and environmental mass yield, EMY) between conventional solution-based protocols and the mechanochemical approach demonstrates a substantial reduction in waste generation while maintaining comparable synthetic performance. Furthermore, the synthesized complexes were directly employed as catalysts in the solvent-free mechanochemical oxidation of diphenylmethanol to benzophenone, highlighting the practical applicability of these Ru(II) systems in sustainable catalytic transformations.