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Cyclopentadienyl ring activation in organometallic chemistry and catalysis

Nature Reviews Chemistry volume 7, pages 561–572 (2023)Cite this article

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Abstract

The cyclopentadienyl (Cp) ligand is a cornerstone of modern organometallic chemistry. Since the discovery of ferrocene, the Cp ligand and its various derivatives have become foundational motifs in catalysis, medicine and materials science. Although largely considered an ancillary ligand for altering the stereoelectronic properties of transition metal centres, there is mounting evidence that the core Cp ring structure also serves as a reservoir for reactive protons (H+), hydrides (H−) or radical hydrogen (H•) atoms. This Review chronicles the field of Cp ring activation, highlighting the pivotal role that Cp ligands can have in electrocatalytic H2 production, N2 reduction, hydride transfer reactions and proton-coupled electron transfer.

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Fig. 1: The active role of Cp ligands in transition metal complexes.
Fig. 2: Discovery timeline of selected ring-activated cyclopentadiene complexes.
Fig. 3: Cyclopentadiene ring activation in H2 production using [Cp*RhIII(NCMe)(bpy)]2+ catalysts.
Fig. 4: Proposed endo-selective protonation and ligand-to-metal proton migration during H2 production using [enCpNHiPrFe(NCMe)(CO)2]+ catalysts107.
Fig. 5: The role of cyclopentadiene ring activation of decamethylcobaltocene in N2 reduction catalysis.
Fig. 6: Metal-to-ligand proton migration for generating reactive PCET donors.
Fig. 7: Ring-activated Cp*Rh and CpCo complexes for hydride and proton transfer.

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Acknowledgements

D.E.P. thanks Rutgers University — Newark and the National Science Foundation (2055097) for support. The authors thank M. Bullock and A. Hansen for constructive comments.

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    Andrew VanderWeide & Demyan E. Prokopchuk

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D.E.P. developed the conceptual framework for this manuscript. All authors contributed to writing and editing the manuscript. All authors reviewed and/or edited the manuscript before submission.

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VanderWeide, A., Prokopchuk, D.E. Cyclopentadienyl ring activation in organometallic chemistry and catalysis. Nat Rev Chem 7, 561–572 (2023). https://doi.org/10.1038/s41570-023-00501-1

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