Mechanistic insights into C-H activation using (phebox)Ir compounds

Ph bisoxazolinyl (Phebox) iridium has been previously shown to catalyze C-H activation of benzene and hydrocarbon chains. The mechanisms for C-H oxidn. in (Phebox)Ir(X)_2 are explored using mechanistic templates previously developed for related NNC pincer compds. using d. functional theory (B3LYP and M06 with solvation). Pathways for both non-radical C-H activation and radical hydrogen atom abstraction are compared. These routes are compared to exptl. data for the activation of mesitylene, including oxidn. and H/D exchange reactions. In particular, we focus on the role of the monodentate ionic ligand (acetate and trifluoroacetic acid) in promoting C-H activation, showing that trifluoroacetic acid can lower non-radical C-H activation barriers. Using the established mechanism, modifications to the Phebox ligand are also explored in order to promote non-radical C-H activation.