β‑Hydride Elimination and C–H Activation by an Iridium Acetate Complex, Catalyzed by Lewis Acids. Alkane Dehydrogenation Cocatalyzed by Lewis Acids and [2,6-Bis(4,4-dimethyloxazolinyl)-3,5-dimethylphenyl]iridium

NaBAr^F₄ (sodium tetrakis­[(3,5-trifluoromethyl)­phenyl]­borate) was found to catalyze reactions of (Phebox)­Ir^III­(acetate) (Phebox = 2,6-bis­(4,4-dimethyloxazolinyl)-3,5-dimethylphenyl) complexes, including (i) β-H elimination of (Phebox)­Ir­(OAc)­(<i>n</i>-alkyl) to give (Phebox)­Ir­(OAc)­(H) and the microscopic reverse, alkene insertion into the Ir–H bond of (Phebox)­Ir­(OAc)­(H), and (ii) hydrogenolysis of the Ir–alkyl bond of (Phebox)­Ir­(OAc)­(<i>n</i>-alkyl) and the microscopic reverse, C–H activation by (Phebox)­Ir­(OAc)­(H), as indicated by H/D exchange experiments. For example, β-H elimination of (Phebox)­Ir­(OAc)­(<i>n</i>-octyl) (<b>2-Oc</b>) proceeded on a time scale of minutes at −15 °C in the presence of (0.4 mM) NaBAr^F₄ as compared with a very slow reaction at 125 °C in the absence of NaBAr^F₄. In addition to NaBAr^F₄, other Lewis acids are also effective. Density functional theory calculations capture the effect of the Na⁺ cation and indicate that it operates primarily by promoting κ²–κ¹ dechelation of the acetate anion, which opens the coordination site needed to allow the observed reaction to proceed. In accord with the effect on these individual stoichiometric reactions, NaBAr^F₄ was also found to cocatalyze, with (Phebox)­Ir­(OAc)­(H), the acceptorless dehydrogenation of <i>n</i>-dodecane