Towards mild conditions by predictive catalysis via sterics in the Ru-catalyzed hydrogenation of thioesters

•Milstein's reported discovery of hydrogenation of thioesters directly toward thiols and alcohols catalyzed by a Ru-acridine.•Reaction mechanism and precise description of the rate determining step described by DFT calculations.•Steric maps via%VBur rationalize the path to milder conditions.•Sterical demanding substituents on the P atoms of the PNP pincer ligands reduces the kinetic cost of the rate determining step.