Bimetallic Bis-NHC-Ir(III) Complex Bearing 2-Arylbenzo[<i>d</i>]oxazolyl Ligand: Synthesis, Catalysis, and Bimetallic Effects

Huang, Shuang; Hong, Xia; Cui, He‐Zhen; Zhan, Bing; Li, Zhiming; Hou, Xiu‐Feng

doi:10.1021/acs.organomet.0c00464

Cited by 31 publications

(21 citation statements)

References 68 publications

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“…In dinuclear complex Ir-4 (Figure ), two five-membered iridacycles are formed, in which the N azo and N amide donor atoms coordinate to the Ir on one side, while N azo and aryl carbon atom of the phenyl ring bind to the Ir on the other side. The distance between the Ir···Ir centers in the dinuclear complex is 4.830 Å, which is relatively shorter than that in the reported dinuclear complexes of Ir(III)–Cp* . The N–N bond distances of the coordinated azo group are in the range of 1.276–1.294 Å, deviating slightly from the free ligand and indicating an unreduced form of the ligand .…”

Section: Results and Discussionmentioning

confidence: 99%

Iridium Azocarboxamide Complexes: Variable Coordination Modes, C–H Activation, Transfer Hydrogenation Catalysis, and Mechanistic Insights

et al. 2021

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Azocarboxamides, a special class of azo ligands, display intriguing electronic properties due to their versatile binding modes and coordination flexibility. These properties may have significant implications for their use in homogeneous catalysis. In the present report, halfsandwich Ir−Cp* complexes of two different azocarboxamide ligands are presented. Different coordination motifs of the ligand were realized using base and chloride abstracting ligand to give N ∧ N-, N ∧ O-, and N ∧ C-chelated monomeric iridium complexes. For the azocarboxamide ligand having methoxy substituted at the phenyl ring, a mixture of N ∧ C-chelated mononuclear (Ir-5) and N ∧ N,N ∧ C-chelated dinuclear complexes (Ir-4) were obtained by activating the C−H bond of the aryl ring. No such C−H activation was observed for the ligand without the methoxy substituent. The molecular identity of the complexes was confirmed by spectroscopic analyses, while X-ray diffraction analyses further confirmed three-legged piano-stool structure of the complexes along with the above binding modes. All complexes were found to exhibit remarkable activity as precatalysts for the transfer hydrogenation of carbonyl groups in the presence of a base, even at low catalyst loading. Optimization of reaction conditions divulged superior catalytic activity of Ir-3 and Ir-4 complexes in transfer hydrogenation over the other catalysts. Investigation of the influence of binding modes on the catalytic activity along with wide range substrates, tolerance to functional groups, and mechanistic insights into the reaction pathway are also presented. These are the first examples of C−H activation in azocarboxamide ligands.

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Section: Results and Discussionmentioning

confidence: 99%

Iridium Azocarboxamide Complexes: Variable Coordination Modes, C–H Activation, Transfer Hydrogenation Catalysis, and Mechanistic Insights

et al. 2021

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“…While the 1 H-NMR spectrum [29][30][31] and high resolution EI mass spectrum [31] of 2-bromo-6-chloromethylpyridine have been obtained, this report, to the best of our knowledge, provides the first collection of the 13 C-NMR spectrum and EI mass spectrum obtained through gas chromatography. Furthermore, while the 2-bromo-6-hydroxymethylpyridine was run through GC-MS analysis by Huang et al [47], they only report the m/z peak of the parent ion with largest relative intensity while this manuscript provides a complete analysis and thorough assignment of the entire GC mass spectrum (EI) of this parent compound including regions of the most predominant ion fragments. These more thorough and detailed characterization methods and analyses of the 2-bromo-6-hydroxymethylpyridine and 2-bromo-6-chloromethylpyridine compounds will assist researchers in monitoring reactions involving use of these compounds.…”

Section: Discussionmentioning

confidence: 99%

Facile Synthesis and Characterization of a Bromine-Substituted (Chloromethyl)Pyridine Precursor towards the Immobilization of Biomimetic Metal Ion Chelates on Functionalized Carbons

Handlovic

Moreira

Khan

et al. 2021

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Multidentate ligands involving tethered pyridyl groups coordinated to transition metal ions have been frequently used to mimic the 3-histidine (3H), 2-histidine-1-carboxylate (2H1C) brace motifs or other combinations of histidine and carboxylate endogenous ligating residues found in bioinorganic metalloenzymes. It is of interest to immobilize these ligand chelates onto heterogeneous supports. This, however, requires the use of bromine-substituted (chloromethyl)pyridines, whose current synthetic routes involve the use of extremely pyrophoric chemicals, such as n-butyllithium that require cryogenic reaction conditions, and toxic chemicals, such as thionyl chloride, that are challenging to handle and require extensive hazard controls. Herein, we report alternative methodologies towards the syntheses of 2-bromo-6-hydroxymethylpyridine and 2-bromo-6-chloromethylpyridine from inexpensive commercially available 2,6-dibromopyridine using isopropylmagnesium chloride lithium chloride complex (Turbo Grignard) and cyanuric chloride which are easier to handle and require milder reaction conditions than the conventional reagents. Gas chromatography-mass spectrometry (GC-MS) methods were developed and simple 1H- and 13C- nuclear magnetic resonance (NMR) and Fourier-transform infrared (FT-IR) spectroscopies were also used to monitor the conversion of both reaction steps and showed that products could be obtained and isolated through simple workups without the presence of unreacted starting material or undesired overchlorinated 2-chloro-6-chloromethylpyridine side product.

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“…Hence, the catalyst loading is 1 mol% sufficient to catalyse the reaction with good-to-excellent yields. [29] It is worth to note that one of the antibacterial drugs, namely, N-(salicylidene)-2-hydroxyaniline, was synthesized from 2-hydroxybenzyl alcohol and 2-amino phenol using our present protocol (Scheme 4), and an excellent yield of 95% was obtained ( Figures S43, S44).…”

Section: S C H E M E 4 Preparation Of N-(salicylidene)-mentioning

confidence: 94%

Arene diruthenium(II)‐mediated synthesis of imines from alcohols and amines under aerobic condition

Tamilthendral

Ramesh

Małecki

2020

Applied Organom Chemis

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The utility and selectivity of the newly synthesized dinuclear arene Ru(II) complex were demonstrated towards the synthesis of imines from coupling of alcohols and amines in the aerobic condition. Analytical and various spectral methods have been used to establish the unprecedented formation of the new thiolato‐bridged dinuclear ruthenium complex. The molecular structure of the titled complex was evidenced with aid of X‐ray crystallographic technique. A wide range of imines were obtained in good‐to‐excellent yields up to 98% and water as the by‐product through an acceptorless dehydrogenative coupling of alcohols with amines. The catalytic reaction operated a concise atom economical without any oxidant with 1 mol% of the catalyst load. Further, the role of base, solvent and catalyst loading of the coupling reaction has been investigated. A plausible mechanism has been described and was found to proceed via the formation of an aldehyde intermediate. Short synthesis of antibacterial drug N‐(salicylidene)‐2‐hydroxyaniline illustrated the utility of the present protocol.

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Bimetallic Bis-NHC-Ir(III) Complex Bearing 2-Arylbenzo[d]oxazolyl Ligand: Synthesis, Catalysis, and Bimetallic Effects

Cited by 31 publications

References 68 publications

Iridium Azocarboxamide Complexes: Variable Coordination Modes, C–H Activation, Transfer Hydrogenation Catalysis, and Mechanistic Insights

Iridium Azocarboxamide Complexes: Variable Coordination Modes, C–H Activation, Transfer Hydrogenation Catalysis, and Mechanistic Insights

Facile Synthesis and Characterization of a Bromine-Substituted (Chloromethyl)Pyridine Precursor towards the Immobilization of Biomimetic Metal Ion Chelates on Functionalized Carbons

Arene diruthenium(II)‐mediated synthesis of imines from alcohols and amines under aerobic condition

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