Unusual oxidative addition pathway of aryl halides to a Rh(I) pincer complex

CECILIA M. GALLEGO; FABIO DOCTOROVICH; JUAN PELLEGRINO

Simposio; 8th Latin American Symposium on Coordination and Organometallic Chemistry; 2022

Oxidative additions (OAs) in transition metal complexes most typically occur via a two-electron transfer from the metal center to the entering ligands, and are often a key step in several catalytic mechanisms. However, they are also mechanistically diverse.[1] In this work, we have studied reaction of Rh(I) complex Rh(PCP)(N2) (1) with several halogenated substrates, RX. Interestingly, the expected OA product Rh(PCP)(R)(X) (2) is not the only -and at times not even the main- product. Instead, an alternate pathway leading to unusual Rh(II) species Rh(PCP)(X) (3) is detected, which although stable, ultimately yields Rh(PCP)(H)(X) (4) by proton transfer from the benzene solvent. The competing pathways can be seen in Figure 1.These reactions have been monitored by 1H, 31P and 19F NMR. An arrange of different substrates (iodobenzene, bromobenzene, chlorobenzene, 2-fluoroiodobenzene, 2-iodotoluene, among others) has been studied in order to understand the prevalence of either pathway, as well as some preliminary studies on the effect of the phosphine substituent of the PCP ligand.Isolation of (3) is also underway since this oxidation state is seldom reported for rhodium. We expect to further understand its redox behavior by cyclic voltammetry, and explore its proton-transfer reactivity.