Drastic improvements in transition metal heterogeneous catalysts have been observed by decreasing catalyst size and anchoring them to a support scaffold. Size reduction offers two important benefits: (i) the number of surface atoms able to participate in catalysis increases, and (ii) the coordination number of the metals decrease, resulting in higher catalytic activity. Since transition metal heterogenous catalysts are widely used in various industries, many studies have focused on smaller scale catalysts. This led to the conception of single-atom catalysts (SACs), a class of catalysts based on isolated metal atoms anchored to a support scaffold. SACs are often much more reactive and can offer better selectivity when compared to nano-scale catalysts. In order to realize the full potential of SACs, a sound understanding of the underlying catalytic mechanisms is required. However, surface analysis tools can become less effective in studying catalytic mechanisms at the atomic scale.<br/> <br/>Mass spectrometry has proven to be a robust technique for studying organometallic catalytic mechanisms at the single-molecule level. Using a modified linear triple quadrupole ion trap mass spectrometer (modified Thermo Electron LTQ XL<sup>TM</sup>) equipped with an electrospray ionization (ESI) source, we can isolate a specific ionic species and probe its reactivity via ion-molecule reactions. By employing established gas-phase synthetic techniques, we have developed the first example of a zero-valent Ni complex that can act as a model ion for a pristine graphene-supported SAC. Reactions with linear, branched, and cyclic alkanes reveal that the Ni SAC model ion is capable of the dehydrogenation of alkanes via two sequential C-H activations: metal insertion into a C-H bond and β-hydride elimination. By introducing energy into the system, additional dehydrogenations occur, enabling processes such as the transformation of cyclohexane to benzene. In addition to the formation of alkenes, the Ni SAC model ion is also capable of selectively producing other unsaturated functional groups, such as imines, via a similar dehydrogenation pathway. Kinetic isotope effects and DFT calculations support the proposed mechanism. Our work suggests that graphene-supported Ni SACs are capable of dehydrogenation via C-H activation.

Dehydrogenation via C-H activation by a graphene-supported nickel single-atom catalyst model ion in the gas phase

Macromolecular Chemistry: The Second Century

[Author Benefits](https://scimeetings.acs.org/?utm_source=pubs_content_marketing&utm_medium=website&utm_campaign=0320_MCF_NPI_Launch_Spring_Homepage&ref=pubs_content_marketing)

[How to use SciMeetings](https://storage.googleapis.com/dl.morressier.com/acs/SciMeetings-ACSSpring2020-HowToGuide_M3020-Final.pdf)

[Frequently Asked Questions](https://storage.googleapis.com/dl.morressier.com/acs/SciMtng_ACSNMSp2020_FAQ_M3120_Final.pdf)

ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.