Synthesis and Resolution of Chiral Ruthenium Complexes Containing the 1-Me-3-PhCp Ligand

Hu, Yue; Shaw, Anthony Peter Gordon; Guan, Huashi; Norton, Jack R.; Sattler, Wesley; Rong, Yi

doi:10.1021/acs.organomet.5b00852

Cited by 5 publications

(4 citation statements)

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“… 17 , 18 Most of these (de)hydrogenation catalysts perform ionic hydrogenation, which is the sequential transfer of H + and H – ; other transition metal-based catalysts for ionic hydrogenation have been reported. 19 − 27 …”

Section: Introductionmentioning

confidence: 99%

“…Carbon dioxide hydrogenation is studied here because 6,6′-dhbp complexes and other pyridinol-based complexes of Ir(III) are especially effective at promoting this reaction and (de)hydrogenation in general. ,− Other highly efficient CO 2 hydrogenation homogeneous catalysts include several different iridium pincer complexes from Nozaki; Brookhart and Meyer; Bernskoetter, Hazari, and Palmore; and others . For formic acid dehydrogenation, a reusable highly active iridium catalyst with a P,N ligand was reported by Williams; other groups have performed formic acid dehydrogenation in the course of methanol dehydrogenation. , Most of these (de)hydrogenation catalysts perform ionic hydrogenation, which is the sequential transfer of H + and H – ; other transition metal-based catalysts for ionic hydrogenation have been reported. − …”

Section: Introductionmentioning

confidence: 99%

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Iridium and Ruthenium Complexes of N-Heterocyclic Carbene- and Pyridinol-Derived Chelates as Catalysts for Aqueous Carbon Dioxide Hydrogenation and Formic Acid Dehydrogenation: The Role of the Alkali Metal

et al. 2017

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Hydrogenation reactions can be used to store energy in chemical bonds, and if these reactions are reversible, that energy can be released on demand. Some of the most effective transition metal catalysts for CO2 hydrogenation have featured pyridin-2-ol-based ligands (e.g., 6,6′-dihydroxybipyridine (6,6′-dhbp)) for both their proton-responsive features and for metal–ligand bifunctional catalysis. We aimed to compare bidentate pyridin-2-ol based ligands with a new scaffold featuring an N-heterocyclic carbene (NHC) bound to pyridin-2-ol. Toward this aim, we have synthesized a series of [Cp*Ir(NHC-pyOR)Cl]OTf complexes where R = tBu (1), H (2), or Me (3). For comparison, we tested analogous bipy-derived iridium complexes as catalysts, specifically [Cp*Ir(6,6′-dxbp)Cl]OTf, where x = hydroxy (4Ir) or methoxy (5Ir); 4Ir was reported previously, but 5Ir is new. The analogous ruthenium complexes were also tested using [(η6-cymene)Ru(6,6′-dxbp)Cl]OTf, where x = hydroxy (4Ru) or methoxy (5Ru); 4Ru and 5Ru were both reported previously. All new complexes were fully characterized by spectroscopic and analytical methods and by single-crystal X-ray diffraction for 1, 2, 3, 5Ir, and for two [Ag(NHC-pyOR)2]OTf complexes 6 (R = tBu) and 7 (R = Me). The aqueous catalytic studies of both CO2 hydrogenation and formic acid dehydrogenation were performed with catalysts 1–5. In general, NHC-pyOR complexes 1–3 were modest precatalysts for both reactions. NHC complexes 1–3 all underwent transformations under basic CO2 hydrogenation conditions, and for 3, we trapped a product of its transformation, 3SP, which we characterized crystallographically. For CO2 hydrogenation with base and dxbp-based catalysts, we observed that x = hydroxy (4Ir) is 5–8 times more active than x = methoxy (5Ir). Notably, ruthenium complex 4Ru showed 95% of the activity of 4Ir. For formic acid dehydrogenation, the trends were quite different with catalytic activity showing 4Ir ≫ 4Ru and 4Ir ≈ 5Ir. Secondary coordination sphere effects are important under basic hydrogenation conditions where the OH groups of 6,6′-dhbp are deprotonated and alkali metals can bind and help to activate CO2. Computational DFT studies have confirmed these trends and have been used to study the mechanisms of both CO2 hydrogenation and formic acid dehydrogenation.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Iridium and Ruthenium Complexes of N-Heterocyclic Carbene- and Pyridinol-Derived Chelates as Catalysts for Aqueous Carbon Dioxide Hydrogenation and Formic Acid Dehydrogenation: The Role of the Alkali Metal

et al. 2017

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“…For example, monodentate amines are well-known ligands for transition metals and are common nucleophiles for organic reactions. In contrast, monodentate thiols, in neutral form, are relatively rare as ligands. , However, sulfur-containing substrates can bind strongly to transition metals and often poison catalysts. − In addition, thiols as sources of ligands − generally afford the thiolate complex. − Nonetheless, thiol complexes have been prepared by ligand substitution, , including a number of Ru porphyrin thiol complexes, Ru(por)(RSH) 2 . In several cases, binding of the thiol is reversible and the complexes are only characterized in situ.…”

Section: Introductionmentioning

confidence: 99%

“…40−45 In addition, thiols as sources of ligands 46−48 generally afford the thiolate complex. 49−52 Nonetheless, thiol complexes have been prepared by ligand substitution, 53,54 including a number of Ru porphyrin thiol complexes, Ru(por)(RSH) 2 . 55 In several cases, binding of the thiol is reversible and the complexes are only characterized in situ.…”

Section: ■ Introductionmentioning

confidence: 99%

Reactivity Comparison of Primary Aromatic Amines and Thiols in E–H Insertion Reactions with Diazoacetates Catalyzed by Iridium(III) Tetratolylporphyrin

2017

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A detailed kinetic study is described for the insertion of carbenes from methyl diazoacetate into the N–H bond of aniline, using Ir(TTP)CH3 (TTP = tetratolylporphyrinato) as a catalyst. Aniline strongly coordinates to the Ir center with a binding constant of K = (2.5 ± 0.5) × 104 at 296 K, forming an inactive hexacoordinate complex, (aniline)Ir(TTP)CH3. The rate of N–H insertion is first order in both diazo ester and catalyst. When the true amount of active, five-coordinate Ir(TTP)CH3 is taken into account, the insertion rate is found to be independent of the aniline concentration. This indicates that the rate-limiting step in the catalytic cycle occurs prior to the nucleophilic attack of aniline on an Ir carbene complex to generate a coordinated ylide. Thus, with N–H insertion catalyzed by Ir(TTP)CH3, aniline is both a strong ligand and a potent nucleophile. This is in contrast to the analogous catalytic insertion of carbenes into S–H bonds. p-Toluenethiol is a more weakly binding ligand toward Ir(TTP)CH3 (K = 680 ± 20 at 296 K). Moreover, the rate of S–H insertion is first order in diazo reagent, catalyst, and thiol concentrations. In this case, the slow step is nucleophilic attack of the thiol on the Ir carbene complex to form a coordinated sulfonium ylide intermediate. In comparison to aniline, p-toluenethiol is a weaker ligand and a poorer nucleophile. The consequence of these differences is that the rate of aniline attack on the carbene intermediate is much faster than the rate of formation of the intermediate carbene complex; whereas the rate of nucleophilic addition of the thiol is slower that the rate of carbene complex formation.

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Spontaneous Resolution by Crystallization of an Octanuclear Iron(III) Complex Using Only Racemic Reagents

et al. 2019

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The P and M enantiomers of the octanuclear [Fe8(μ4‐O)4(μ‐4‐Cl‐pz)12Cl4] complex, having T symmetry, were resolved by temporary substitution of chloride ligands by racemic 4‐sBu‐phenolates and subsequent crystallization, where the (S)‐ and (R)‐phenolates coordinate selectively to the M and P complexes, respectively. The complexes were characterized by circular dichroism analysis and X‐ray structure determination. This work constitutes a rare example of enantiomeric recognition resulting in spontaneous resolution upon crystallization.

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Synthesis and Resolution of Chiral Ruthenium Complexes Containing the 1-Me-3-PhCp Ligand

Cited by 5 publications

References 91 publications

Iridium and Ruthenium Complexes of N-Heterocyclic Carbene- and Pyridinol-Derived Chelates as Catalysts for Aqueous Carbon Dioxide Hydrogenation and Formic Acid Dehydrogenation: The Role of the Alkali Metal

Iridium and Ruthenium Complexes of N-Heterocyclic Carbene- and Pyridinol-Derived Chelates as Catalysts for Aqueous Carbon Dioxide Hydrogenation and Formic Acid Dehydrogenation: The Role of the Alkali Metal

Reactivity Comparison of Primary Aromatic Amines and Thiols in E–H Insertion Reactions with Diazoacetates Catalyzed by Iridium(III) Tetratolylporphyrin

Spontaneous Resolution by Crystallization of an Octanuclear Iron(III) Complex Using Only Racemic Reagents

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