ortho-C–H Activation of Thiobenzoic Acid: Synthesis, Characterization, and Reactivity of Iridium Thiobenzoate Complexes

Cp*Ir(Me 2 SO)(OAc) 2, 1, has been shown to activate an ortho -C–H-bond of thiobenzoic acid in methanol at 100 °C to form the novel iridium complex (Cp*Ir(S(O)CC 6 H 4 )) 2, 5 . Unlike the similar reaction with benzoic acid, this new iridium complex exists as a dimer with bridging sulfur ligands. To our knowledge, this is the first example of metal facilitated C–H activation of thiobenzoic acid. Complex 5 reacted with CO to form Cp*Ir(CO)(S(O)CC 6 H 4 ), 6 . Complex 5 was also shown to react with the electrophilic methyl reagents methyl iodide and methyl triflate. The reaction with methyl iodide resulted in the formation of Cp*Ir(I)(SMe(O)CC 6 H 4 ), 7, while the reaction with methyl triflate resulted in the bimetallic complex [(Cp*Ir(SMe(O)CC 6 H 4 )(Cp*Ir(S(O)CC 6 H 4 )][OTf], 8 . The order of reactivity with electrophilic methyl reagents was MeOTf > MeI >MeOAc, which reflects the nucleophilic character of the sulfoxyl group of the cyclometalated thiobenzoate ligand. Attempts at cyclization with complex 5 and olefins and alkynes were not successful. In addition, C–I reductive elimination reactions of 7 to form S -methyl 2-iodobenzothioate were not observed.