The ligand 2,2’-bipyridine (bpy) is well known to support metal centers that engage in reductive catalysis, but the exact role of the easily reduced bpy system in promoting such reactivity is often unclear. For example, Cp*Rh(bpy) (Cp* = pentamethylcyclopentadienyl) is an effective proton-reduction catalyst that shows involvement of reduced bpy character in certain intermediates, but the role of this ligand in the mechanism of H–H coupling remains elusive. To provide new insights into the role of the bpy ligand in the properties and reactivity of this family of compounds, a ligand platform was targeted with a donor profile similar to bpy but with a less-accessible lowest unoccupied molecular orbital (LUMO) to limit its ability to participate in backdonation. The chosen framework retains two pyridine moieties but lacks the interring conjugation that is responsible for the ability of bpy to accept additional electron density. This attenuation in backbonding engenders substantial differences in the properties of the half-sandwich rhodium complexes of this bis(pyridyl) ligand vs. its conjugated analogue bpy as determined via structural, spectroscopic, and electrochemical studies. The structural and electronic features of these complexes, as well as their contribution to H<sub>2</sub> evolution reactivity, will be discussed.

Rhodium complexes ligated by an unconjugated bipyridine analogue: Electronic properties and effects on H<sub>2</sub> evolution reactivity

255th National Meeting (2018)

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Rhodium complexes ligated by an unconjugated bipyridine analogue: Electronic properties and effects on H2 evolution reactivity

Rhodium complexes ligated by an unconjugated bipyridine analogue: Electronic properties and effects on H₂ evolution reactivity