Acyliridium(III) Complexes with PCN Terdentate Ligands Including Imino‐ or Iminium‐Acyl Moieties or Formation of Hydrido from Hydroxyl

Formation of Irida-β-ketoimines and PCNamine-Ir(III) Complexes by Reacting Irida-β-diketones with Aliphatic Diamines: Catalytic Activity in Hydrogen Release by Methanolysis of H3N-BH3

Aliphatic diamines [(H2N(CH2)nNHR) (a-d) n = 2: R = H (a), R = CH3 (b), R = C2H5 (c), n = 3, R = H (d) or rac-2-(aminomethyl)piperidine (e)] react with [IrH(Cl){(PPh2(o-C6H4CO))2H}] in THF to afford ketoimine complexes [IrH(Cl){(PPh2(o-C6H4CO))(PPh2(o-C6H4CN(CH2)nNHR))H}] (2a-2d) or [IrH(Cl){(PPh2(o-C6H4CO))(PPh2(o-C6H4CNCH2(C5H9NH)))H}] (2e), containing a bridging N-H···O hydrogen bond and a dangling amine. Complex 2e consists of an almost equimolar mixture of two diastereomers. In protic solvents, the dangling amine in complexes 2 displaces chloride to afford cationic acyl-iminium compounds, [IrH(PPh2(o-C6H4CO))(PPh2(o-C6H4CNH(CH2)nNHR))]X (3a-3d, X = Cl) or [IrH(PPh2(o-C6H4CO))(PPh2(o-C6H4CNHCH2(C5H9NH)))]Cl (3e) and (4a-4b, X = ClO4), with new hemilabile terdentate PCNamine ligands adopting a facial disposition. Complexes 3 contain the corresponding phosphorus atom trans to hydride and the amine fragment trans to acyl, while complexes 4 contain the amine trans to hydride. 3b and 4b consist of 80:20 and 95:5 mixtures of diastereomers, respectively, while 3e contains a 65:35 mixture. In the presence of KOH, intermediate cationic acyl-iminium complexes 3 transform into neutral acyl-imine [IrH(PPh2(o-C6H4CO))(PPh2(o-C6H4CN(CH2)nNHR))] derivatives (5) with retention of the stereochemistry. Single-crystal X-ray diffraction analysis was performed on 2a, [3a]Cl, [3b]Cl, [4a]ClO4, and 5b. Complexes 2, 3, and 5 catalyze the methanolysis of ammonia-borane under air to release hydrogen. The highest activity is observed for ketoimine complexes 2.

Alkynyl Ligands as Building Blocks for the Preparation of Phosphorescent Iridium(III) Emitters: Alternative Synthetic Precursors and Procedures

Alkynyl ligands stabilize dimers [Ir(μ-X)(3b)₂]₂ with a cis disposition of the heterocycles of the 3b ligands, in contrast to chloride. Thus, the complexes of this class—cis-[Ir(μ₂-η²-C≡CPh){κ²-C,N-(C₆H₄-Isoqui)}₂]₂ (Isoqui = isoquinoline) and cis-[Ir(μ₂-η²-C≡CR){κ²-C,N-(MeC₆H₃-py)}₂]₂ (R = Ph, ^tBu)—have been prepared in high yields, starting from the dihydroxo-bridged dimers trans-[Ir(μ-OH){κ²-C,N-(C₆H₄-Isoqui)}₂]₂ and trans-[Ir(μ-OH){κ²-C,N-(MeC₆H₃-py)}₂]₂ and terminal alkynes. Subsequently, the acetylide ligands have been employed as building blocks to prepare the orange and green iridium(III) phosphorescent emitters, Ir{κ²-C,N-[C(CH₂Ph)Npy]}{κ²-C,N-(C₆H₄-Isoqui)}₂ and Ir{κ²-C,N-[C(CH₂R)Npy]}{κ²-C,N-(MeC₆H₃-py)}₂ (R = Ph, ^tBu), respectively, with an octahedral structure of fac carbon and nitrogen atoms. The green emitter Ir{κ²-C,N-[C(CH₂^tBu)Npy]}{κ²-C,N-(MeC₆H₃-py)}₂ reaches 100% of quantum yield in both the poly(methyl methacrylate) (PMMA) film and 2-MeTHF at room temperature. In organic light-emitting diode (OLED) devices, it demonstrates very saturated green emission at a peak wavelength of 500 nm, with an external quantum efficiency (EQE) of over 12% or luminous efficacy of 30.7 cd/A.

Acetylide ligands have been employed as building blocks to prepare orange and green iridium(III) phosphorescent emitters, with an octahedral structure of fac carbon and nitrogen atoms. In OLED devices, the emitter Ir{κ²-C,N-[C(CH₂^tBu)Npy]}{κ²-C,N-(MeC₆H₃-py)}₂ demonstrates very saturated green emission at a peak wavelength of 500 nm, with a luminous efficacy of 30.7 cd/A.

Preparation and Degradation of Rhodium and Iridium Diolefin Catalysts for the Acceptorless and Base-Free Dehydrogenation of Secondary Alcohols

Rhodium and iridium diolefin catalysts for the acceptorless and base-free dehydrogenation of secondary alcohols have been prepared, and their degradation has been investigated, during the study of the reactivity of the dimers [M(μ-Cl)(η⁴-C₈H₁₂)]₂ (M = Rh (1), Ir (2)) and [M(μ-OH)(η⁴-C₈H₁₂)]₂ (M = Rh (3), Ir (4)) with 1,3-bis(6′-methyl-2′-pyridylimino)isoindoline (HBMePHI). Complex 1 reacts with HBMePHI, in dichloromethane, to afford equilibrium mixtures of 1, the mononuclear derivative RhCl(η⁴-C₈H₁₂){κ¹-N_py-(HBMePHI)} (5), and the binuclear species [RhCl(η⁴-C₈H₁₂)]₂{μ-N_py,N_py-(HBMePHI)} (6). Under the same conditions, complex 2 affords the iridium counterparts IrCl(η⁴-C₈H₁₂){κ¹-N_py-(HBMePHI)} (7) and [IrCl(η⁴-C₈H₁₂)]₂{μ-N_py,N_py-(HBMePHI)} (8). In contrast to chloride, one of the hydroxide groups of 3 and 4 promotes the deprotonation of HBMePHI to give [M(η⁴-C₈H₁₂)]₂(μ-OH){μ-N_py,N_iso-(BMePHI)} (M = Rh (9), Ir (10)), which are efficient precatalysts for the acceptorless and base-free dehydrogenation of secondary alcohols. In the presence of KO^tBu, the [BMePHI]⁻ ligand undergoes three different degradations: alcoholysis of an exocyclic isoindoline-N double bond, alcoholysis of a pyridyl-N bond, and opening of the five-membered ring of the isoindoline core.

Irida-β-ketoimines Derived from Hydrazines To Afford Metallapyrazoles or N-N Bond Cleavage: A Missing Metallacycle Disclosed by a Theoretical and Experimental Study

Unprecedented metallapyrazoles [IrH₂{Ph₂P(o-C₆H₄)CNNHC(o-C₆H₄)PPh₂}] (3) and [IrHCl{Ph₂P(o-C₆H₄)CNNHC(o-C₆H₄)PPh₂}] (4) were obtained by the reaction of the irida-β-ketoimine [IrHCl{(PPh₂(o-C₆H₄CO))(PPh₂(o-C₆H₄CNNH₂))H}] (2) in MeOH heated at reflux in the presence and absence of KOH, respectively. In solution, iridapyrazole 3 undergoes a dynamic process due to prototropic tautomerism with an experimental barrier for the exchange of ΔG_coal^⧧ = 53.7 kJ mol^-1. DFT calculations agreed with an intrapyrazole proton transfer process assisted by two water molecules (ΔG = 63.1 kJ mol^-1). An X-ray diffraction study on 4 indicated electron delocalization in the iridapyrazole ring. The reaction of the irida-β-diketone [IrHCl{(PPh₂(o-C₆H₄CO))₂H}] (1) with H₂NNRR' in aprotic solvents gave irida-β-ketoimines [IrHCl{(PPh₂(o-C₆H₄CO))(PPh₂(o-C₆H₄CNNRR'))H}] (R = R' = Me (5); R = H, R' = Ph (8)), which can undergo N-N bond cleavage to afford the acyl-amide complex [IrHCl(PPh₂(o-C₆H₄CO))(PPh₂(o-C₆H₄C(O)N(CH₃)₂))-κP,κO] (6) or [IrHCl(PPh₂(o-C₆H₄CO))(PPh₂(o-C₆H₄CN)-κP)(NH₂NHPh-κNH₂)] (9) containing o-(diphenylphosphine)benzonitrile and phenylhydrazine, respectively. From a CH₂Cl₂/CH₃OH solution of 9 kept at -18 °C, single crystals of [IrHCl(PPh₂(o-C₆H₄CO))(PPh₂(o-C₆H₄CN)-κP))(HN═NPh-κNH)] (10) containing o-(diphenylphosphine)benzonitrile and phenyldiazene were formed, as shown by X-ray diffraction. The reaction of 1 with methylhydrazine in methanol gave the hydrazine complex [IrCl(PPh₂(o-C₆H₄CO))₂(NH₂NH(CH₃)-κNH₂)] (7). Single-crystal X-ray diffraction analysis was performed on 6 and 7.