Dirhodium (II,II) paddlewheel complexes have been utilized and explored extensively in various carbene transfer reactions such as C-H functionalization, ylide formation, and cyclopropanation reactions. Reactivity has been modulated through modification of the carbene and/or bridging ligands of the dirhodium (II,II) paddlewheel complexes. Research has shown that reactivity can also be tuned through tethered dirhodium (II,II) paddlewheel complexes by altering the electronic nature of the tether. The tether allows for electron donation through the Rh-Rh bond which affects the coordination of incoming ligands at the distal rhodium site. Currently, there is no way to predict how newly designed tether dirhodium (II,II) paddlewheel complexes might behave in a given transformation. We have recently developed oxazolidinone bridging ligands to incorporate a pendant thioether. Axial coordination can then be explored using this scaffold and through modification of the sulfur tether. Modifications include changing the substituent off the sulfur atom (Ph vs. Me), altering the methylene units (1 vs. 2), and exploring the effects of having an oxidized sulfur atom. These scaffolds have been explored in the cyclopropanation reaction with styrene and ethyl diazoacetate (EDA). A structure-activity correlation has been determined via association constants using UV-vis to gain a better understanding of the impact on the equilibrium kinetics of diazo-mediated carbene transfer reactions and whether there is a direct correlation with product yields.

Structure-activity correlations of tethered thioether Rh (II) paddlewheel complexes in cyclopropanation reactions

ACS Spring 2022

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