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

Zumeta, Itziar; Mendicute‐Fierro, Claudio; Rodríguez‐Diéguez, Antonio; Seco, José M.; Garralda, María A.

doi:10.1002/ejic.201600056

Cited by 6 publications

(15 citation statements)

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“…The Ir(1)–C(21) bond is disposed trans to the pyridyl group of a (C(7),N(1))-iminyl-pyridine moiety (C(21)–Ir(1)–N(1) = 169.13(15)°), which has a N(1)–Ir(1)–C(7) bite angle of 74.85(15)°. The iridium–pyridine distance of 2.236(4) Å (Ir(1)–N(1)) is slightly longer than those found in 7 and 8 , whereas the Ir(1)–C(7) bond length of 1.982(4) Å is about 0.02 Å shorter than the Ir(1)–C(21) single bond and even shorter than those reported for other iridium-iminyl derivatives . This suggests that, for an adequate description of the Ir(1)–C(7) bonding situation, the resonance form a shown in Chart should also be taken into account.…”

Section: Resultsmentioning

confidence: 76%

“…The iridium–pyridine distance of 2.236(4) Å (Ir(1)–N(1)) is slightly longer than those found in 7 and 8 , whereas the Ir(1)–C(7) bond length of 1.982(4) Å is about 0.02 Å shorter than the Ir(1)–C(21) single bond and even shorter than those reported for other iridium-iminyl derivatives. 30 This suggests that, for an adequate description of the Ir(1)–C(7) bonding situation, the resonance form a shown in Chart 1 should also be taken into account. Atom C(7) is disposed trans to the hydroxide group with a C(7)–Ir(1)–O(1) angle of 151.58(14)°, while the other part of the double bridge, the azavinylidene ligand, lies trans to the C(25)–C(26) double bond.…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2021

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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)(η 4 -C 8 H 12 )] 2 (M = Rh ( 1 ), Ir ( 2 )) and [M(μ-OH)(η 4 -C 8 H 12 )] 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(η 4 -C 8 H 12 ){κ 1 - N py -(HBMePHI)} ( 5 ), and the binuclear species [RhCl(η 4 -C 8 H 12 )] 2 {μ- N py , N py -(HBMePHI)} ( 6 ). Under the same conditions, complex 2 affords the iridium counterparts IrCl(η 4 -C 8 H 12 ){κ 1 - N py -(HBMePHI)} ( 7 ) and [IrCl(η 4 -C 8 H 12 )] 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(η 4 -C 8 H 12 )] 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 t Bu, 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.

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Section: Resultsmentioning

confidence: 76%

Section: Resultsmentioning

confidence: 99%

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

et al. 2021

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“…We have recently shown that hydrazine reacts with the irida-β-diketone [IrHCl{(PPh 2 ( o -C 6 H 4 CO)) 2 H}] ( 1a ) to give the ketoimine-type complex [IrHCl{(PPh 2 ( o -C 6 H 4 CO))(PPh 2 ( o -C 6 H 4 CNNH 2 ))H}] ( 2 ) (Chart ). Complex 2 is similar to other irida-β-ketoimines obtained from ammonia or aliphatic primary amines . The latter easily undergo hydrolysis or deprotonation in protic media at room temperature, which were not observed for 2 .…”

Section: Introductionmentioning

confidence: 73%

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

et al. 2016

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Unprecedented metallapyrazoles [IrH{PhP(o-CH)CNNHC(o-CH)PPh}] (3) and [IrHCl{PhP(o-CH)CNNHC(o-CH)PPh}] (4) were obtained by the reaction of the irida-β-ketoimine [IrHCl{(PPh(o-CHCO))(PPh(o-CHCNNH))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 = 53.7 kJ mol. DFT calculations agreed with an intrapyrazole proton transfer process assisted by two water molecules (ΔG = 63.1 kJ mol). An X-ray diffraction study on 4 indicated electron delocalization in the iridapyrazole ring. The reaction of the irida-β-diketone [IrHCl{(PPh(o-CHCO))H}] (1) with HNNRR' in aprotic solvents gave irida-β-ketoimines [IrHCl{(PPh(o-CHCO))(PPh(o-CHCNNRR'))H}] (R = R' = Me (5); R = H, R' = Ph (8)), which can undergo N-N bond cleavage to afford the acyl-amide complex [IrHCl(PPh(o-CHCO))(PPh(o-CHC(O)N(CH)))-κP,κO] (6) or [IrHCl(PPh(o-CHCO))(PPh(o-CHCN)-κP)(NHNHPh-κNH)] (9) containing o-(diphenylphosphine)benzonitrile and phenylhydrazine, respectively. From a CHCl/CHOH solution of 9 kept at -18 °C, single crystals of [IrHCl(PPh(o-CHCO))(PPh(o-CHCN)-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(PPh(o-CHCO))(NHNH(CH)-κNH)] (7). Single-crystal X-ray diffraction analysis was performed on 6 and 7.

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“…MeOH assisted BÀ N bond cleavage in the trimethoxy substituted adduct H 3 NÀ B(OMe) 3 leads to the observed [NH 4 ][B-(OMe) 4 ] final product as in the related AB hydrolysis. [11,17] Taking into account i) that coordinated boranes are liable to undergo H 2 O nucleophilic attack; [20,22] ii) the ability of methanol solutions of transient dihydridobis(acyldiphenylphosphine)(III) species to release hydrogen with formation of hydride derivatives by O-to-Ir hydrogen transfer from a hydroxyl fragment; [32] and iii) the present experimental evidences, we may propose a simplified mechanism for the methanolysis of AB catalysed by irida-βdiketones, shown in Scheme 4, which represents a general catalytic cycle that can be applied to all the three succesive steps leading to the hydrogen release.…”

Section: Resultsmentioning

confidence: 99%

Efficient Homogeneous Hydridoirida‐β‐Diketone‐Catalyzed Methanolysis of Ammonia‐Borane for Hydrogen Release in Air. Mechanistic Insights

et al. 2021

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The hydridoirida-β-diketone [(IrH{(PPh 2 (o-C 6 H 4 CO)) 2 H}) 2 (μ-Cl)][BF 4 ] (2) has been used as a homogeneous catalyst for the methanolysis of ammonia-borane to release up to 3 equivalents of hydrogen in the presence of air. With catalyst loadings as low as 0.2 mol%, ammonia-borane undergoes methanolysis within 6 min at 30°C, with TOF 50% of 320 mol H2 • mol Ir À 1 • min À 1 , or within 80 s at 60°C, with an excellent TOF 50% of 1991 mol H2 • mol Ir À 1 • min À 1 , and maintains its catalytic activity in consecutive runs. Triethylamine-borane fails to undergo methanolysis. Kinetic studies indicate first-order dependence on substrate and on catalyst concentration and suggest cleavage of the solvent OÀ H bond being involved in the rate determining step of the reaction. In methanol solution 2 forms cationic [IrH (MeOH){(PPh 2 (o-C 6 H 4 CO)) 2 H}] + (3) and reacts with Me 3 NÀ BH 3 to afford a hydridoirida-β-diketone [IrH(Me 3 NBH 3 ){(PPh 2 (o-C 6 H 4 CO)) 2 H}] + (4), with the borane adduct η 1 -coordinated to iridium. Compound [4][BAr F 4 ] shows dynamic behaviour in solution due to exchange of bridging and terminal BÀ H bonds. A multinuclear NMR study of the catalyzed reaction shows the formation of two ammonia-methoxyborane adduct intermediates, H 3 NÀ BH 2 (OCH 3 ) and H 3 NÀ BH(OCH 3 ) 2 , and an iridium species proposed of the hydridodiacyl type [IrH (H 3 NBH 3À x (OCH 3 ) x )(PPh 2 (o-C 6 H 4 CO)) 2 ] with a coordinated borane adduct. On account of experimental evidence, a simplified catalytic cycle is suggested for the methanolysis of AB to release hydrogen.

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

Cited by 6 publications

References 64 publications

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

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

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

Efficient Homogeneous Hydridoirida‐β‐Diketone‐Catalyzed Methanolysis of Ammonia‐Borane for Hydrogen Release in Air. Mechanistic Insights

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