New play in the chemical-reaction playbook uncovered

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https://science.psu.edu/news/new-play-in-chemical-reaction-playbook-uncovered

New play in the chemical-reaction playbook uncovered
Researchers at Penn State show that one of the fundamental reactions in transition metal chemistry can proceed by a different order of events, achieving the same outcome

Sam Sholtis
22 July 2025

Speeding up chemical reactions is key to improving industrial processes or mitigating unwanted or harmful waste. Realizing these improvements requires that chemists design around documented reaction pathways. Now, a team of Penn State researchers has found that a fundamental reaction called oxidative addition can follow a different path to achieve the same ends, raising the question of whether this new order of events has been occurring all along and potentially opening up new space for chemical design.

A paper describing the research appeared June 23, 2025 in the Journal of the American Chemical Society.

The reactions of organic compounds — those containing carbon, hydrogen, oxygen and a few other elements — are limited by the bonding patterns and electron arrangements specific to organic elements. More electron arrangements are available in transition metals, another type of element that includes, for example, platinum and palladium. When transition metals interact with organic compounds, this added layer of complexity can modify the electron structure of organic compounds leading to a wider diversity of potential reactions, including breaking chemical bonds and catalyzing reactions not possible among purely organic compounds. Understanding the diversity of ways these chemical reactions can occur could help chemists design ways to exploit transition metals to increase the efficiency of industrial processes or find new solutions that could, for example, help reduce environmental pollutants, according to the researchers.

“Transition metals have properties that allow them to ‘break the rules’ of organic chemistry,” said Jonathan Kuo, assistant professor of chemistry in the Eberly College of Science at Penn State and the leader of the research team. “As an example, even though biological systems are largely considered to be organic, much of the chemistry in cells occurs at active sites, where metallic co-factors actually drive the reactivity. Transition metals are also used to catalyze industrial-scale chemical reactions. General understanding as to how these reactions work is a way to approach the efficiency of nature or even invent reactions that don’t have a known analogy in nature.”

Chemical reactions occur because the atoms that compose molecules “want” to be in a state that is more stable. This stabilization is accomplished mainly by rearranging electrons amongst orbitals — the cloudlike regions around atomic nuclei where electrons are likely to be located. A hydrogen atom, for example, has only one electron that lives in a “1s” orbital. However, two hydrogen atoms can bond to make dihydrogen (H2), where the two 1s orbitals mix to make two hybrid orbitals. The more stable of the two hybrid orbitals hosts the two electrons, resulting in a net energy savings and more stability. Larger, more complex elements can have multiple s-orbitals with different energy levels as well as p-, d- and f-orbitals, which have varied shapes and capacity, leading to more diversity in electronic structure and more possible types of chemical reactions.

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Net Oxidative Addition of H₂ to {M¹¹}²⁺+ (M = Pd, Pt) by Heterolysis and Protic Rebound
Nisha Rao and Jonathan L. Kuo
Journal of the American Chemical Society 2025 147 (26), 22351-22357
DOI: 10.1021/jacs.5c07140