Utrecht Chemists Uncover Mechanism for Designing Sustainable Molecular Catalysts

Utrecht scientists, under the supervision of Marc-Etienne Moret, have discovered a new mechanism to build molecular catalysts. The new mechanism involves the earth-abundant metal nickel instead of precious metals that are often used as part of molecular catalysts. Moret: “This discovery initiates a new area of research that brings about a whole new concept for the design of more sustainable catalysts.”

In 2017, chemistry researcher Marc-Etienne Moret received an ERC Starting Grant to study new catalysts with better properties. Now, with the discovery that was published in the scientific journal Nature Chemistry, his team has made a big step towards the goal he set out to achieve back then: the development of a new family of catalysts based on non-noble metals. “We discovered a new reaction mechanism”, Moret says enthusiastically. “This does not happen very often, especially in a field that’s been researched so thoroughly.”

We are very eager to pursue this new research direction

Pharmaceuticals and colour pigments

Researchers María Sansores-Paredes, Martin Lutz, and Moret found a new, more sustainable mechanism to activate hydrogen. Activating hydrogen is an important step in the development of molecular catalysts, which facilitate the synthesis of fine chemicals, such as pharmaceuticals and colour pigments. Usually, the activation of hydrogen needs a precious metal, such as rhodium, iridium, or ruthenium. These metals are effective but also expensive, scarce, and potentially harmful to the environment. Moret’s team revealed a new mechanism to activate hydrogen with the earth-abundant element nickel.

Tailormade molecule

To activate the hydrogen through this new process, Moret’s team used a tailormade molecule that surrounds the metal. This special type of molecule is called a pincer ligand and includes an olefin, which is an organic compound that contains a double bond between two carbon atoms. Instead of the hydrogen directly attaching to the metal, the researchers observed through spectroscopy, a process called ligand-to-ligand hydrogen transfer: the hydrogen moved directly from the hydrogen molecule attached to the metal to the olefin molecule. “We can directly ‘see’ two forms of the catalyst, one with an intact hydrogen molecule bound to the metal, and another one in which the hydrogen is split over nickel and carbon atoms”, Moret explains. In addition, computer models predict the existence of a transition state that connects the two observable forms.

What’s next?

Moret will continue to explore what can be done with the newly found mechanism. Perhaps it can be applied to other metals, or to other bonds. In fact, while the current paper was under review, Moret’s group demonstrated that the new mechanism can be applied to a carbon-hydrogen bond, which is something he is particularly excited about. “Organic molecules have many carbon-hydrogen bonds. So, if we manage to apply this new mechanism to these bonds, the synthesis of fine chemicals will eventually be much quicker. I am very eager to pursue this new research direction.”