Oxidation of hydrocarbons into higher value products is an important class of reaction for the chemical industry. One strategy for homogeneous catalytic C–H functionalization utilizes non-d0 transition metal complexes in which the metal cycles between Mn and Mn+2 oxidation states during the catalytic cycle. Thus, modulating the relative stability of the Mn and Mn+2 states is key to optimizing catalytic activity. For example, if the Mn+2 state is too stable the catalytic activity is inhibited as reductive elimination of R–X is unfavorable. Hence, understanding ligand effects on reductive functionalization reactions is one key to designing efficient catalysts. In many cases, oxidation from Rh(I) to Rh(III) occurs with the binding of a sixth ligand to give an 18-electron, octahedral complex. In this presentation, a set of “capping arene” ligands that sterically block one of the coordination sites on the Rh metal center is studied. The ligands featuring an azaindole backbone (5-XFP) place the capping arene farther away from the Rh metal center while the ligands featuring a quinoline backbone (6-XFP) place the capping arene closer to the Rh metal center; the latter increases the potential of an η2 interaction between the Rh center and the arene ring. The effects of the different ligands on reductive elimination reactions will be presented.

Study of ligand effects on reductive elimination from Rh complexes

ACS Spring 2022

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