The addition of a silicon-hydrogen or a boron-hydrogen bond across a carbon-carbon multiple bonds is a well-established method for the introduction of versatile silane and borane functional groups to base hydrocarbon feedstocks. Transition metal catalysis, historically with precious second- and third- row transition metals, has been used to broaden the scope of the hydrofunctionalization reaction, improve reaction rate and enhance selectivity. The anti-Markovnikov selectivity of platinum-catalyzed hydrosilylation of alkenes, for example, is an enabling synthetic technology in the multibillion-dollar silicones industry. Increased emphasis on sustainable catalytic methods and more economic processes has shifted focus to catalysis with more earth-abundant transition metals such as iron, cobalt and nickel. This review describes contemporary approaches and offers a contextual analysis of catalytic alkene hydrosilylation and hydroboration reactions using first-row transition metals. Emphasis is placed on defining advances in the field, what constitutes catalyst cost, safety, and important design features to enable precious metal-like reactivity, as well as new chemistry that is unique to first-row transition metals.

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Earth-Abundant Transition Metal Catalysts for Alkene Hydrosilylation and Hydroboration: Opportunities and Assessments.

The last two decades have seen an impressive improvement of the use of iron as a fascinating and valuable alternative transition metal in homogeneous catalysis in terms of sustainability and economy. It was efficiently used in catalytic organic synthetic transformations, which in particular include the reduction of unsaturated bonds. This review summarizes the fast development and the recent advances in selective reductions of olefins, alkynes, carbonyl and carboxylic derivatives, imines, and nitro compounds promoted by iron catalysts. The topical hydrogen-borrowing reactions and hydroboration of unsaturated compounds are also reported. It is hoped that this account not only provides an overview of the state of the art in iron catalysis but also stimulates the development of superior greener catalytic systems in the near future.

Iron Catalysis in Reduction and Hydrometalation Reactions.

Recent Advances in Hydrometallation of Alkenes and Alkynes via the First Row Transition Metal Catalysis

Cobalt has become increasingly attractive in homogeneous catalysis because of its unique characteristics and outstanding catalytic performance in addition to being cheap and earth-abundant. Hydride transfer processes are involved in a broad range of organic transformations that allow the facile preparation of various useful chemicals and synthetic building blocks. These reactions have continuously received great attention both from academia and industry. In this perspective, we review homogeneous cobalt-catalyzed hydride transfer reactions according to the classified reaction types and provide a comprehensive overview of the design, synthesis, and reactivity of cobalt catalysts, their catalytic applications, and reaction mechanisms.

Hydride Transfer Reactions Catalyzed by Cobalt Complexes.

A Pharmaceutical Industry Perspective on Sustainable Metal Catalysis

First-row, earth-abundant metals offer an inexpensive and sustainable alternative to precious-metal catalysts. As such, iron and cobalt catalysts have garnered interest as replacements for alkene and alkyne hydrofunctionalization reactions. However, these have required the use of air- and moisture-sensitive catalysts and reagents, limiting both adoption by the non-expert as well as applicability, particularly in industrial settings. Here, we report a simple method for the use of earth-abundant metal catalysts by general activation with sodium tert-butoxide. Using only robust air- and moisture-stable reagents and pre-catalysts, both known and, significantly, novel catalytic activities have been successfully achieved, covering hydrosilylation, hydroboration, hydrovinylation, hydrogenation and [2π+2π] alkene cycloaddition. This activation method allows for the easy use of earth-abundant metals, including iron, cobalt, nickel and manganese, and represents a generic platform for the discovery and application of non-precious metal catalysis.

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Activation and discovery of earth-abundant metal catalysts using sodium tert -butoxide

https://pubs.rsc.org/en/content/articlepdf/2017/cc/c7cc01085k

Cobalt-catalysed Markovnikov selective hydroboration of vinylarenes

Olefin hydroboration reactions provide efficient access to synthetically versatile and easily handled organoboronic esters. In this study, we demonstrate that the commercially available organoboran...

/pdf/a-boron-boron-double-transborylation-strategy-for-the-3obaizvp06.pdf

A Boron–Boron Double Transborylation Strategy for the Synthesis of gem-Diborylalkanes

Arene C(sp2)-H bond borylation reactions provide rapid and efficient routes to synthetically versatile boronic esters. While iridium catalysts are well established for this reaction, the discovery and development of methods using Earth-abundant alternatives is limited to just a few examples. Applying an in situ catalyst activation method using air-stable and easily handed reagents, the iron-catalysed C(sp2)-H borylation reactions of furans and thiophenes under blue light irradiation have been developed. Key reaction intermediates have been prepared and characterised, and suggest two mechanistic pathways are in action involving both C-H metallation and the formation of an iron boryl species.

https://www.mdpi.com/1420-3049/25/4/905/pdf

Andrew P. Dominey

Papers

Activation and discovery of earth-abundant metal catalysts using sodium tert -butoxide

Cobalt-catalysed Markovnikov selective hydroboration of vinylarenes

A Boron–Boron Double Transborylation Strategy for the Synthesis of gem-Diborylalkanes

Iron-Catalysed C(sp2)-H Borylation Enabled by Carboxylate Activation.

Manganese-Catalyzed C(sp2)‒H Borylation of Furan and Thiophene Derivatives