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 (η⁵-C₅Me₅)­Ir­(III) unit coordinated to cyclometalated bis­(aryl)­phosphine ligands, PR′(Ar)₂, for R′ = Me and Ar = 2,4,6-Me₃C₆H₂, <b>1b</b>; 2,6-Me₂-4-OMe-C₆H₂, <b>1c</b>; 2,6-Me₂-4-F-C₆H₂, <b>1d</b>; R′ = Et, Ar = 2,6-Me₂C₆H₃, <b>1e</b>. Both chloride- and hydride-containing compounds, <b>2b</b>–<b>2e</b> and <b>3b</b>–<b>3e</b>, respectively, are described. Reactions of chlorides <b>2</b> with NaBAr_F (BAr_F = B­(3,5-C₆H₃(CF₃)₂)₄) in the presence of CO form cationic carbonyl complexes, <b>4</b>^<b>+</b>, with ν­(CO) values in the narrow interval 2030–2040 cm^–1, indicating similar π-basicity of the Ir­(III) center of these complexes. In the absence of CO, NaBAr_F forces κ⁴-<i>P</i>,<i>C</i>,<i>C</i>′,<i>C</i>″ coordination of the metalated arm (studied for the selected complexes <b>5b</b>, <b>5d</b>, and <b>5e</b>), 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 κ⁴ species <b>5d</b> and <b>5e</b> into the corresponding hydrido phosphepine complexes <b>6d</b> and <b>6e</b>. Using CD₃OD as the source of deuterium, the chlorides <b>2</b> undergo deuteration of their 11 benzylic positions whereas hydrides <b>3</b> 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

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 (η⁵-C₅Me₅)­Ir­(III) unit coordinated to cyclometalated bis­(aryl)­phosphine ligands, PR′(Ar)₂, for R′ = Me and Ar = 2,4,6-Me₃C₆H₂, <b>1b</b>; 2,6-Me₂-4-OMe-C₆H₂, <b>1c</b>; 2,6-Me₂-4-F-C₆H₂, <b>1d</b>; R′ = Et, Ar = 2,6-Me₂C₆H₃, <b>1e</b>. Both chloride- and hydride-containing compounds, <b>2b</b>–<b>2e</b> and <b>3b</b>–<b>3e</b>, respectively, are described. Reactions of chlorides <b>2</b> with NaBAr_F (BAr_F = B­(3,5-C₆H₃(CF₃)₂)₄) in the presence of CO form cationic carbonyl complexes, <b>4</b>^<b>+</b>, with ν­(CO) values in the narrow interval 2030–2040 cm^–1, indicating similar π-basicity of the Ir­(III) center of these complexes. In the absence of CO, NaBAr_F forces κ⁴-<i>P</i>,<i>C</i>,<i>C</i>′,<i>C</i>″ coordination of the metalated arm (studied for the selected complexes <b>5b</b>, <b>5d</b>, and <b>5e</b>), 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 κ⁴ species <b>5d</b> and <b>5e</b> into the corresponding hydrido phosphepine complexes <b>6d</b> and <b>6e</b>. Using CD₃OD as the source of deuterium, the chlorides <b>2</b> undergo deuteration of their 11 benzylic positions whereas hydrides <b>3</b> 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