As previously mentioned, a key issue in optimizing the performance of Cp * Rh complexes has been the inability to experimentally isolate an active Rh(III)H species. For the tested full complexes, Reaction 2 is experimentally either too favorable (bpy), making the Rh(III)H species too fleeting to study, or not favorable enough (dppm, dppb, dppx), leaving an inactive Rh(III)H species. If Reaction 2 can be tuned to be slightly less favorable than the bpy complex without deactivating Reactions 1 and 3, this could allow for an active Rh(III)H species to be isolated. Based on the 5 kcal/mol gap in ∆∆E R2 Y between the 75 • P(c 4 ) and the bpy complex, along with the known inactivity of all the full phosphorus complexes tested here, swapping nitrogen linkers with phosphorus will likely stabilize the Rh(III)H species too much for the catalyst to remain active. The stability of the Rh(III)H species could be tuned by using a nitrogen linker that produces a wider bite angle compared to bpy. This may provide just enough of a decrease in reactivity for the Rh(III)H species to be isolated. While in-creasing the bite angle does make Reaction 3 less favorable, the scans suggest that it could be made as wide as 100 • without increasing the ∆∆E R3 X more than 2.5 kcal/mol, a small enough change where the reaction should still occur. Reaction 1 only becomes more favorable with increased bite angle, so this step should remain reactive. From published work, [Cp * Rh] complexes supported by bis(2-pyridyl)methane ligands (dpma), a ligand that forms a sixmembered chelate ring, do appear to be sufficiently basic to take up protons at the metal center. However, precisely tuning the bite angle may be synthetically challenging and any effect on the reactivity could be offset by nonspecific interactions from bulky groups introduced in the process. As an alternative or complementary approach, one could tune the electronics of the structure, particularly the charge on the rhodium. For the models, swapping nitrogen and phosphorus linkers had a large effect on the reactivity which seemed to stem from their ability to withdraw charge from the rhodium. By attaching electron-donating substituents to N(c 3 ) ligand scaffolds (or electronwithdrawing substituents to P(c 4 ) ligand scaffolds), the charge on the rhodium can be tuned to an intermediate value between that of the bpy and phosphorus complexes. An intermediate charge should lead to an intermediate reactivity.