Tethered Axial Coordination as a Control Element on Dirhodium Paddlewheel Complexes

Abstract: Dirhodium(II,II) paddlewheel (RhII) complexes can mediate a number of transformations through the catalytic transfer of carbenes from diazo precursors. The reactivity and selectivity of these reactions are modulated partly by the modification bridging ligands surrounding the metal center, but the axial sites of the catalysts are often overlooked as a control element. This presentation will detail our current research efforts to probe the benefits of axial coordination by designing RhII complexes with tethered Lewis basic groups onto traditional bridging ligands. In initial studies, thioether ligands proved to be the most robust Lewis base when tethered to oxazolindinate or carboxylate bridging ligands. The novel complexes were then used in diazo-mediated cyclopropanation reactions, Si−H reactions, and C−H insertion reactions. The results of the experiments, along with spectroscopic and computational analyses, provided insight into the role that tethered axial coordination plays in diazo-mediated reactions. This presentation will also discuss our efforts to develop a chromogenic detector based on RhII complexes to detect organophosphate nerve agents by their hydrolysis by-products.

Bio: Ampofo Darko received his B.S. in chemistry from Guilford College and his Ph.D. from the University of Florida, where he studied tungsten-catalyzed oxidative carbonylation of functionalized amines under the direction of Prof. Lisa McElwee-White. He then performed postdoctoral research with Prof. Joseph Fox at the University of Delaware studying trans-cyclooctenes and their bioorthogonal reactivity with tetrazines. He joined the faculty at the University of Tennessee in 2014, with research interests at the interface of organic and inorganic chemistry. His group is interested in using nature as an inspiration for organometallic catalyst design, cycloaddition reactions, and organocatalysis.

Please join us for a reception with Dr. Darko at 3:00 PM in Hand 1134.
Hosted by Dr. Miguel Munoz