(294d) Importing Hydroformylation Catalysts on Electrode Surfaces Unlocks Novel Voltage-Driven Reactivity

Organometallic catalyst motifs on electrode surfaces are an exciting prospect. They promise new chemical transformations that simultaneously exploit both the potent physical handle of applied voltage and the highly-tailored reactivities of organometallic catalysts. Hydroformylation (HFN) is a well-studied thermochemical reaction that performs C-C coupling by appending CO onto an olefin, in the presence of H₂, to generate an aldehyde. HFN requires elevated temperatures (90 – 120^oC) and pressures (7 – 25 bar) as well as precious metal (Rh) catalysts.

In this work, we import HFN catalysts onto electrode surfaces and describe how the electrified interface perturbs and enhances reactivity. We show that the first-order, thermodynamic effect of applied potential is to supply a reductive driving force and supplant the need for H₂ as a reactant. Instead, protons, electrons, and CO can be used to hydroformylate a model olefin. This electrochemical HFN reaction shows distinct reaction kinetics from thermochemical HFN, suggesting that voltage unlocks new reaction pathways that are distinct from the thermochemical case, and that the role of voltage is not simply to generate H₂ gas in situ. Applied potential may also perturb HFN-like sites via non-Faradaic effects. Therefore, we use in situ XANES spectroscopy to determine how applied potential affects catalyst electronic structure during reaction conditions. We will discuss the mechanistic implications of these results, with particular emphasis on discussing how HFN catalysis changes as it is made to “traverse” the thermochemical/electrochemical divide.

Ultimately, the additional handle of applied potential may improve the hydroformylation reaction by reducing the need for flammable reactants, elevated temperatures/pressures, or even precious metal catalysts. Additionally, achieving electrochemical C-C coupling at an electrode surface is a difficult task that has interesting implications for electrochemical energy conversion. More generally, this work will provide design principles useful for importing promising thermochemical catalysts onto electrode surfaces.