From there, Rh(III)H reacts with an acid to release dihydrogen, and an acetonitrile molecule from the solvent then binds to form Rh(III)A (Reaction 2). The cycle ends with an electrochemical reduction that regenerates Rh(I) (Reaction 3), closing the catalytic cycle. Based on the most recent kinetic data, protonation of the Cp * ring via proton-hydride tautomerism may not contribute significantly to catalysis under conditions involving strong acid (Reaction 1a). Previous work has demonstrated that with an attached bipyridyl (bpy) ligand, the catalyst readily forms dihydrogen gas. Efforts to further optimize the catalytic activity of this complex have been stymied by an inability to isolate the reactive Rh(III)H intermediate supported by bpy. On the other hand, if the bpy ligand is replaced with bis(diphenylphosphino) methane (dppm), 24 bis(diphenylphosphino)benzene (dppb), or bis(diphenylphosphino)-9,9'-dimethylxanthene (dppx), the Rh(III)H species can be generated but is stabilized significantly, implying from experimental work that Reaction 2 is no longer favorable and cannot proceed, even upon exposure of the Rh(III)H species to strong acid(s). Clearly the reactivity of these complexes is strongly influenced by the supporting bidentate chelating ligand, but it is not apparent what ligand features (e.g., donor atom identity, metal-ligand bite angle, or steric bulk) promote or hinder catalysis. Although previous computational studies have investigated the mechanism for H 2 generation, this study tries to understand in detail what the role of the ligand is, which may provide key insights for the design of better catalysts. The ligand-based features of these structures have then been systematically varied to ascertain their effect on the reaction energy of each step. As any trends among these simplified structures could inform strategies to tune the reactivity of more experimentally relevant complexes, we calculated the relative reaction energies for a collection of potential catalysts in order to determine if they could be rationalized based on the ligand features.