Iridium(III) main-group compound interactions: Chemistry from iridium(I) iridates to iridium(V) cations

Chapter 1. Nucleophilic iridates and dihydridoiridium-organoaluminum adducts were synthesized by reaction of Cp*(PMe₃)IrH₂ (1) with organoaluminum and organomagnesium compounds. Triarylaluminum compounds were reacted with 1 to produce complexes of the general form Cp*(PMe ₃)IrH₂·AlR₃ (3a, 3b ). Thermolyses of these compounds eliminated R-H and gave unisolable formal Ir(II) species, Cp*(PMe₃)Ir(H)AlR₂, in low yields. However, reaction of AlEt₃ with 1 gave the Ir(I) centrosymmetric dimer, (Cp*(PMe₃)IrAlEt)₂ (4). Reaction of diarylmagnesium compounds with 1 produced Ir(II) dimers of the general form (Cp*(PMe₃)Ir(H)MgR)₂ (5, 6) or (Cp*(PMe₃)Ir(H))₂Mg (7). Solution studies confirmed that the organomagnesium-iridium compounds exist as a mixture of rapidly interconverting cisoid and transoid dimers in solution. Reaction of the iridates 4–7 with CO₂ gave the reduced iridium-carbonyl species Cp*(PMe₃)IrCO. These iridates are thermally stable synthons for a variety of difficult-to-synthesize Ir(III) complexes such as Cp*(PMe₃)IrHD (1-d), Cp*(PMe₃)IrD₂ (1-d ₂) and the hydridoformyl complex Cp*(PMe₃)Ir(H)CHO in good yields. The Ir(II) iridates were also employed to form hydridoalkyliridium complexes demonstrating that they are versatile precursors for synthetic applications in organometallic iridium chemistry.; Chapter 2. Unlike reactions of Cp*(PMe₃)IrH ₂ with organoaluminum or organomagnesium compounds, reaction of Cp*(PMe ₃)IrMe₂ (1) with organomain-group compounds generally produced decomposition. The exception to this pattern was reaction of 1 with triphenylaluminum which gave Cp*(PMe₃)IrMePh by ligand metathesis. However, reaction of 1 with catalytic amounts of tris(pentafluorophenyl)borane (2) activated benzene- d₆ to readily form Cp*(PMe₃)IrMe(C₆D ₅) and CH₃D. This product distribution indicates that the reaction does not occur by 1-electron transfer catalysis mechanism. Instead, a mechanism relying on the formation of a methyliridium cation is proposed. Reaction of 1 with borane 2 in methylene chloride at −84°C cleanly formed [Cp*(PMe₃)IrMe(ClCH₂Cl)] +[MeB(C₆F₅)₃]− (3). The reactivity of 3 was found to be similar to that of the previously known analogous methyliridium cation [Cp*(PMe ₃)IrMe(ClCH₂Cl)]+[B(3,5-(CF₃) ₂C₆H₃)₄]−.; Chapter 3. The novel mononuclear cationic iridium hydride complex [Cp*(PMe₃)Ir(H)(ClCH₂Cl)]+[MeB(C ₆F₅)₃]− can be generated at low temperature by treatment of [Cp*(PMe₃)IrMe(ClCH₂Cl)] +[MeB(C₆F₅)₃]− with H₂. This hydridoiridium cation reacts with CO, ethylene, and THF to produce thermally robust adducts of the form [Cp*(PMe₃)Ir(H)(L)] +[MeB(C₆F₅)₃]−. Reaction with aldehydes formed the conventional C-H activation-carbonyl deinsertion products [Cp*(PMe₃)IrR(CO)]+[MeB(C₆F ₅)...