Top 5 Reactions Where Iridium Catalysis Shines

Behind many of today's advanced medicines, materials, and energy systems is iridium catalyst doing the heavy lifting. Known for its precision and durability, iridium helps chemists carry out reactions that would otherwise be slow or inefficient. Here are five examples of why iridium catalysis has become so important.

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Asymmetric Hydrogenation-Precision at the Molecular Level

Asymmetric hydrogenation is arguably the most celebrated application of iridium catalysis. Hydrogenation of unsaturated compounds, such as alkenes or imines, affords chiral products with very high enantioselectivity in this reaction. Iridium complexes, particularly those bearing chiral phosphine or N-heterocyclic carbene ligands, are effective for substrates that are poorly activated or sterically hindered.

This makes iridium different in that it is able to hydrogenate unfunctionalised or even minimally substituted alkenes, which usually present problems to the rhodium or ruthenium-based systems. These Ir catalysts have shown precise stereochemistry control while working at considerably moderate pressures and temperatures. This makes them indispensable in pharmaceutical syntheses since the absolute configuration of a molecule can influence biological activity or safety.

In industry, the iridium-catalysed asymmetric hydrogenation finds broad applications in the manufacture of APIs, agrochemicals, and fine chemicals, for which reproducibility of optical purity is not open to negotiation.

C–H Borylation – Direct Functionalization Made Easy

C–H borylation is a significant method in organic synthesis, and the catalytic agent for this reaction involves iridium catalysts. This means that, conventionally, carbon–hydrogen bonds were not directly functionalisable unless some preactivation steps, like halogenation, were performed. Iridium-catalysed C–H borylation enables the direct transformation of these inert C–H bonds into versatile C–B bonds.

Iridium complexes with bipyridine and phenanthroline ligands exhibit exceptionally high selectivity and efficiency, especially in aromatic and heteroaromatic systems. Obtained boronic esters are highly valued intermediates because of easy transformation to alcohols, amines, or carbon-carbon bonds by cross-coupling reactions.

This is of particular significance in medicinal chemistry, where the ability to perform a late-stage functionalisation enables the chemists to rapidly diversify lead compounds. Iridium catalysis therefore enables predictable regioselectivity, reducing trial-and-error and shortening development timelines.

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Transfer Hydrogenation – Hydrogen without Hydrogen Gas

Another area of excellence of iridium catalysis is transfer hydrogenation. In these reactions, the use of molecular hydrogen is avoided and hydrogen donors such as alcohols, formic acid, or amines are considered. Iridium catalysts efficiently mediate hydrogen transfer in a way that is safer and sometimes more practical than traditional methods of hydrogenation.

It is for this reason that iridium-based systems are considerably more robust and tolerant to various functional groups. For this, it serves well in the hydrogenation of ketones, aldehydes, and imines in complex molecules. The reactions often proceed under mild conditions, minimising side reactions and protecting sensitive functionalities.

Transfer hydrogenation also fits well within the framework of green chemistry from a sustainability point of view. Thus, iridium catalysis supports safer laboratory practices and scalable industrial processes by avoiding high-pressure hydrogen gas and using more benign hydrogen sources.

Olefin Isomerization – Controlled Double Bond Rearrangement

Isomerization of olefins includes the changes in the position or geometry of carbon-carbon double bonds. However, although it may sound easy, it is difficult to achieve high selectivity without over-reduction and polymerisation. The reactions are highly controlled by iridium catalysts.

Iridium hydride complexes can selectively isomerise terminal alkenes into internal alkenes or control its E/Z geometry with high stereoselectivity. This is of prime importance in fragrance chemistry, synthesis of polymer precursors, and fine chemicals preparations, where the position of a double bond has a direct influence on physical and chemical properties.

Compared to other transition metals, iridium often can control reaction pathways in a superior manner that allows the chemist to tune molecular structures rather than rely on an equilibrium mixture.

Water Oxidation and Energy-Related Redox Reactions

Apart from organic syntheses, iridium catalysis is also indispensable in energy-related chemistry, such as in water oxidation. Iridium oxide and molecular iridium complexes belong to the most active catalysts of the oxygen evolution reaction—a crucial step in hydrogen production by water splitting.

Iridium's high resistance to corrosion and oxidation enables it to perform under those harsh electrochemical conditions associated with an efficient OER. Although the scarcity and cost of iridium are too high to enable widespread use, it nevertheless remains the benchmark catalyst against which new materials are measured.

In particular, Ir catalysis is directly related to renewable energy technologies such as PEM electrolyzers and research on artificial photosynthesis.

Table 1: Important Reactions Where Iridium Catalysis has Key Advantages

For more comparison, please check Stanford Advanced Materials (SAM).

Conclusion

Iridium catalysis holds a singularly powerful position in the palette of modern chemistry, affording unparalleled selectivity, functional group tolerance, and stability to the most demanding conditions. It enables precision asymmetric synthesis, from academic curiosities to industrial processes, and drives key steps forward in renewable energy technologies. Iridium will continue shaping the future of catalysis.

Reference:

[1] Yanhui Yu, Gai Li, Yutong Xiao, Chi Chen, Yuhang Bai, Tianjiao Wang, Jing Li, Yingjie Hua, Daoxiong Wu, Peng Rao, Peilin Deng, Xinlong Tian, Yuliang Yuan, Iridium-based electrocatalysts for acidic oxygen evolution reaction, Journal of Energy Chemistry, Volume 103, 2025, Pages 200-224, ISSN 2095-4956.

[2] ACS green chemistry institute (n.d.). Metal-Catalysed Borylation via C-H Activation. Retrieved 19/12/2025.