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Lecture

Homogeneous Hydrogenation Mechanisms

In course

CH-422: Catalyst design for synthesis

This course on homogeneous catalysis provide a detailed understanding of how these catalysts work at a mechanistic level and give examples of catalyst design for important reactions (hydrogenation, olefin metathesis, cross-coupling). ...

Description

This lecture delves into the mechanistic differences between neutral Wilkinson's catalyst and cationic catalysts in the context of homogeneous hydrogenation of olefins. It explores the two major mechanistic regimes, 'hydrogen first' and 'olefin-first', followed by a discussion on advantageous properties of a specific catalyst. The lecture also covers the potential of Rh(triphos)Cl as a hydrogenation catalyst for alkenes and the concept of asymmetric hydrogenation using chiral transition metal complexes. Various bidentate chiral phosphines are examined for their role in achieving high enantioselectivity in hydrogenation reactions, leading to the development of a commercialized asymmetric process. The lecture concludes with an overview of different chiral ligands and their impact on metal-catalyzed reactions.

Instructor

Xile Hu

Xile Hu was born in 1978 in Putian, southeastern China. He entered the Peking University in Beijing in 1996. Besides learning too little chemistry, his biggest regret in the college was not able to correct his southern accent in Mandarin. After graduated from PKU, he went to the United States and began his doctoral studies at the University of California, San Diego. In December 2004, he finished with a Ph.D. in chemistry and some fond memories of the beautiful city of San Diego. He then moved to the Los Angeles area and become a postdoctoral scholar at the California Institute of Technology. There he enjoyed numerous stimulating scientific (and other) discussions with friends and colleagues. He also made plenty of friends outside the campus and was a frequent in many local Chinese restaurants. In 2007, after two pleasant visits to Switzerland, he decided to move across the continent one more time and join the faculty of the École Polytechnique Fédérale de Lausanne (EPFL). He now directs the Laboratory of Inorganic Synthesis and Catalysis and is interested in developing chemistry for synthesis, energy and sustainability.

Official source

Ontological neighbourhood

Chemistry

Organic chemistry: Organometallic chemistry

Related concepts (32)

Asymmetric hydrogenation

Asymmetric hydrogenation is a chemical reaction that adds two atoms of hydrogen to a target (substrate) molecule with three-dimensional spatial selectivity. Critically, this selectivity does not come from the target molecule itself, but from other reagents or catalysts present in the reaction. This allows spatial information (what chemists refer to as chirality) to transfer from one molecule to the target, forming the product as a single enantiomer.

Hydrogenation

Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically constitutes the addition of pairs of hydrogen atoms to a molecule, often an alkene. Catalysts are required for the reaction to be usable; non-catalytic hydrogenation takes place only at very high temperatures.

Catalysis

Catalysis (kəˈtæləsɪs) is the process of change in rate of a chemical reaction by adding a substance known as a catalyst (ˈkætəlɪst). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quickly, very small amounts of catalyst often suffice; mixing, surface area, and temperature are important factors in reaction rate. Catalysts generally react with one or more reactants to form intermediates that subsequently give the final reaction product, in the process of regenerating the catalyst.

Wilkinson's catalyst

Wilkinson's catalyst is the common name for chloridotris(triphenylphosphine)rhodium(I), a coordination complex of rhodium with the formula [RhCl(PPh3)3], where 'Ph' denotes a phenyl group). It is a red-brown colored solid that is soluble in hydrocarbon solvents such as benzene, and more so in tetrahydrofuran or chlorinated solvents such as dichloromethane. The compound is widely used as a catalyst for hydrogenation of alkenes. It is named after chemist and Nobel laureate Sir Geoffrey Wilkinson, who first popularized its use.

Homogeneous catalysis

In chemistry, homogeneous catalysis is catalysis where the catalyst is in same phase as reactants, principally by a soluble catalyst a in solution. In contrast, heterogeneous catalysis describes processes where the catalysts and substrate are in distinct phases, typically solid-gas, respectively. The term is used almost exclusively to describe solutions and implies catalysis by organometallic compounds. Homogeneous catalysis is an established technology that continues to evolve.

Related lectures (32)

Catalysis: Hydrogenation

Covers the topic of catalysis, focusing on the process of hydrogenation and the advantages of using soluble catalysts.

Hydrogenation Mechanism

Delves into the detailed reaction mechanism of hydrogenation, emphasizing Wilkinson's catalyst and the impact of ligand design.

Alkene Metathesis: Mechanisms and Applications

Explores alkene metathesis mechanisms, total synthesis strategies, and hydrogenation selectivities.

Catalytic Functionalization of Olefins

Explores catalytic reactions for olefin functionalization, covering asymmetric allylation, hydrogenation, isomerization, hydroamination, hydroboration, and radical reactions.

Hydrogenation Catalysts