Events

Accessing High Energy Electrons and New Modes of C-H Activation with Earth-Abundant Metals

Presented by Prof. Demyan Prokopchuk
Hosted by Prof. Ged Parkin

Abstract:
The sustainable delivery of electrons and activation of C-H bonds continue to be critical areas of research in the energy and synthesis sectors. To this end, our research is focused on capturing high energy electrons housed within organometallic redox mediators and leveraging C-H bonds in chelating ligand frameworks to move around protons (H⁺), hydrides (H^-) and hydrogen atoms (H•). We have recently isolated one of the most potent organometallic redox agents in existence¹ and shown that an amine-rich cyclopentadienyl ligand (Cp^N3) coordinated to iron facilitates electrocatalytic H₂production in the presence of exogenous acid.² In the latter case, the mechanism of H₂ production involves stereoselective endo-Cp^N3 protonation to forge a new C-H bond followed by ligand-to-metal proton transfer – a surprising result because Cp ligands are often considered quintessential “spectator” ligands in catalysis.³ In a separate endeavor, we are interested in understanding the magnitude of C(sp³)-H bond weakening when an alkane moiety interacts with a transition metal (i.e., agostic interactions). To study the C-H bond strength properties, we use diamondoid pincer ligands coordinated to Ni and Pd, which provide unique insights into the thermochemical requirements for C-H activation with unactivated alkanes.⁴ By carefully measuring equilibria in nonpolar solvents, we are able to directly compare the differences in agostic C-H bond strengths between Ni and Pd, providing insights as to why Pd is often “better” at C-H activation than Ni.

1.     J. Am. Chem. Soc. 2024, 146, 19279.
2.     ACS Catal. 2023, 13, 13650.
3.     Nat. Rev. Chem. 2023, 7, 561.
4.     J. Am. Chem. Soc. 2022, 144, 12632.

Read more about the Prokopchuk Lab here