Publication in Nature Communications

11. 11. 2013 | Susan

Enzyme-inspired approach leads to success in synthetic catalysis
Enzymes, the natural catalysts, are generally orders of magnitude more selective than their synthetic counterparts.

Now Professor Joost Reek and co-workers have demonstrated that an enzyme-like approach can substantially enhance the performance of synthetic ‘transition metal catalysts’. Their results have recently been published in Nature Communications.

Catalysis results in shorter synthetic routes and less waste per quantity of product. It facilitates the sustainable production of chemicals in bulk as well as in the fine chemicals and pharmaceutical industries. Especially in the latter two so-called transition metal catalysis is one of the more powerful tools of the chemical engineer. It provides for, amongst others, enhanced selectivity in the chemical transformations. This results in a higher yield of the desired chemical product and reduces the amounts of unwanted by-products.

Nature-inspired
Transition metal catalysts consist of a molecular complex in which a metal atom is surrounded by specific molecular groups. These so-called ligands largely determine the properties of the catalyst by dictating the reactivity and accessibility of the central atom. Catalyst optimization therefore traditionally implies tuning the electronic and spatial (steric) properties of the ligands.

Now research led by professor Joost Reek of the Homogeneous and Supramolecular Catalysis Group at the Van ‘t Hoff Institute for Molecular Sciences demonstrates the feasibility of a new, nature-inspired approach of transition metal catalysis. The Reek team shows that embedding the catalyst in enzyme-like cavities, formed by a self assembly process of programmed building blocks, is a very effective way of enhancing the catalytic selectivity.

The research, published last week in Nature Communications, focusses on the use of a rhodium catalyst in the  conversion of alkenes to aldehydes (hydroformylation). It clearly demonstrates the selectivity in which the product is formed is solely steered by changing the cavity surrounding the metal complex. By using encapsulated catalysts Reek and co-workers achieved a unique selectivity which has never been obtained by traditional catalysts.
 
Rhodium catalyst in the small cage (pink) leads to the formation of the 2-aldehyde, whereas the rhodium catalyst in the big cage (blue) leads to the formation of the 3-aldehyde. The non-encapsulated version of the catalyst leads to a 1:1 formation of both products. Traditional manners of controlling the selectivity in transition metal catalysis fail for this difficult reaction.

 

Rhodium catalyst in the small cage (pink) leads to the formation of the 2-aldehyde, whereas the rhodium catalyst in the big cage (blue) leads to the formation of the 3-aldehyde. The non-encapsulated version of the catalyst leads to a 1:1 formation of both products. Traditional manners of controlling the selectivity in transition metal catalysis fail for this difficult reaction.


ERC Advanced Grant

Reek expects that future generations of transition metal catalysts will increasingly include enzyme-like features in order to achieve selective functionalization of challenging substrate molecules. He will further pursue his approach in a project for which he received a prestigious 2.5 million euro Advanced Grant of the European Research Council. An important part will be devoted to the development of catalyst for water oxidation, and for proton and nitrogen reduction reactions, which are relevant for the development of solar to fuel devices.

Read more on the ERC Advanced Grant for Joost Reek