Cyclometalated Iridium Complexes of Bis(Aryl) Phosphine Ligands: Catalytic C-H/C-D Exchanges and C-C Coupling Reactions

This work details the synthesis and structural identification of a series of complexes of the (eta(5)-C5Me5)Ir(III) unit coordinated to cyclometalated bis(aryl)phosphine ligands, PR'(Ar)(2), for R' = Me and Ar = 2,4,6-Me3C6H2, 1b; 2,6-Me-2-4-OMe-C6H2, 1c; 2,6-Me-2-4-F-C(6)Hz, 1d; R' = Et, Ar = 2,6-Me2C6H3, le. Both chloride- and hydride-containing compounds, 2b-2e and 3b-3e, respectively, are described. Reactions of chlorides 2 with NaBArF (BArF = B(3,5-C6H3(CF3)(2))(4)) in the presence of CO form cationic carbonyl complexes, 4(+), with v(CO) values in the. narrow interval 2030-2040 cm(-1), indicating similar g-basicity of the Ir(III) center of these complexes. In the absence of CO, NaBArF forces kappa(4)-P,C,C',C '' coordination of the metalated arm (studied for the selected complexes 5b, 5d, and 5e), a binding mode so far encountered only when the phosphine contains two benzylic groups. A base-catalyzed intramolecular, dehydrogenative, C-C coupling reaction converts the, kappa(4) species 5d and Se into the corresponding hydrido phosphepine complexes 6d and 6e. Using CD3OD as the source of deuterium, the chlorides 2 undergo deuteration of their 11 benzylic positions whereas hydrides 3 experience only D incorporation into the Ir-H and Ir-CH2 sites. Mechanistic schemes that explain this diversity have come to light thanks to experimental and theoretical DFT studies that are also reported.