Neutrons Uncover Clues for Better Catalysts

Nickel hydride catalyst

CINS Scattering Spotlight: Dr. Manar Shoshani

Source: Mitchell DiPasquale 
Image: A) 1.5 mm3 single crystalline nickel-hydride for neutron diffraction. B) Neutron diffraction-solved structure. C) ChemDraw depiction of cluster.

From cleaning the toxic exhausts of your car’s engine, to the green promise of plastic upcycling, to the biological processes that keep you alive – achieving efficient results in chemical changes is driven by catalysts.

The ability of nature to selectively carry out multi-electron chemistry under ambient conditions has long inspired catalytic design.  Innovation in synthetic catalysts can unlock novel reactions and allow cheaper, cleaner, and more efficient pathways to new and improved materials.

Dr. Manar Shoshani
Dr. Manar Shoshani

Former UWindsor PhD student Manar Shoshani took inspiration from multi-metallic enzyme active sites to try to emulate this robust reactivity in homogenous transition metal clusters. Under the guidance of Dr. Samuel A. Johnson, Manar sought to understand how the multi-metal centres interact to promote catalysis, with hopes of providing a trajectory toward intelligent design of better catalysts. 

With molecular nickel-hydride clusters, Manar observed remarkable activations of C–C, C–O, and C–S bonds as well as catalytic activation of C–H bonds, all of which proceeded rapidly at room temperature. Knowledge on the solid-state structure of the complex is vital to decipher the mechanistic intricacies that drive these processes.

“Determining the unambiguous solid-state structure of these complexes is imperative to understanding both the properties of the cluster, as well as the potential for these clusters to serve as catalysts.”

– Dr. Manar Shoshani, Caltech Post-Doctoral Fellow

Synthetic chemists naturally lean on X-ray crystallography for structural information; however, light atoms (particularly hydrogen), coordinated in these complexes are largely invisible to studies by X-ray. For Manar, neutron diffraction served as the ideal complement to be able to pinpoint the hydride locations in the cluster, and to clue into the details of metal-metal cooperativity.

A step further, as neutrons interact with hydrogen and deuterium differently, the experiment also provided insight into the catalytic hydrogen-deuterium exchange activity of the clusters. Neutrons offer an exceptional means to uncover the finesse of transition metal hydride catalysts. A deeper understanding of metal-metal cooperativity can help usher in a new wave of efficiency with rationally designed catalysts.

After completing his PhD, Dr. Shoshani continues to contribute to catalyst innovation as a post-doctoral fellow at the California Institute of Technology.

For more information on this work, the published manuscript can be found at Shoshani, Manar M., Robert Beck, Xiaoping Wang, Matthew J. McLaughlin, and Samuel A. Johnson. Inorganic Chemistry 57, 5 (2017): 2438-2446.

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