Heterogeneous catalysts are often employed as they tend to have high stability, activity, lower catalyst loadings, and scalability. However, selective heterogeneous catalyst discovery is hindered by a lack of understanding and often relies on high-throughput screening. In contrast, homogeneous catalysts have active sights that are well understood, highly tunable, uniform, and thus highly selective. Immobilization of homogeneous catalysts onto surfaces allows for direct control of active sites, thus providing insights into processes at heterogeneous surfaces. Previous work from our lab showed that the electric field effects on the Re(bpy-S)(CO)3Cl bound to Au surfaces changed the v(CO) frequency by greater than 25 cm-1 over 1 V. This change is three to four times larger than those achieved through synthetic efforts of modifying the bipyridine for electron-donating or accepting groups via Hammett parameters. While these results were significant, this system was not suitable for accessing the effects these fields have on reactivity at a surface. Hydride transfer is one of the fundamental catalytic transformations. The thermodynamic ability for a substrate to donate or accept a hydride, known as hydricity, is highly dependent on the electronic properties of the substrate. To study the effects of hydride transfer on a heterogeneous surface in the presence of an external field, two new Ir catalysts with surface-immobilizable disulfides have been synthesized and their attachment to Au has been characterized. Preliminary computational results show that electric fields stabilize the transfer of a hydride from Ir(Cp*)(bpy)H, making Ir a better hydride donor. To confirm these results, current work is focused on understanding their reactivities with hydrides and several other X-type ligands (CN-, SCN-). Using surface-sensitive IR techniques, these reactions are monitored with work focusing on the change in reactivity due to applied bias.

Surface reactivity of iridium piano-stool complexes bound to gold

ACS Fall 2021

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