Special Issue "Iridium Complexes"

A special issue of Inorganics (ISSN 2304-6740). This special issue belongs to the section "Organometallic Chemistry".

Deadline for manuscript submissions: closed (30 September 2019).

Special Issue Editor

Prof. Dr. Ken-ichi Fujita
E-Mail Website
Guest Editor
Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku Kyoto, Japan
Interests: organometallic chemistry; synthetic organic chemistry; coordination chemistry; dehydrogenation of organic molecules; hydrogen transfer reactions; hydrogen storage using organic hydrides; hydrogen production from sustainable resources
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Special Issue Information

Dear Colleagues, 

For a long period of time, intensive studies have been conducted on iridium complexes. For example, a detailed study on the reactivity of the Vaska's complex, which was performed mainly in the 1960s, contributed to the development of organometallic chemistry. Recently, stoichiometric reactions involving iridium complexes, such as C–H and C–C bond cleavage, have been studied by many researchers and greatly helped to deepen the basic understanding of extremely difficult substrate conversion reactions.

Lately, studies that consider iridium complex as a functional material have vigorously progressed. For example, iridium complexes have attracted significant interest as light emitting materials. Some known complexes have already been developed to a practical level. Furthermore, the catalytic chemistry of iridium complexes is currently in the developmental phase; not only utilizations in conventional hydrogenation reactions, but also a number of publications on new catalytic systems for C–H borylation, allylic substitution, dehydrogenative oxidation of organic substrates, etc. have been appeared.

In this Special Issue, we intend to reveal new functions of iridium complexes and to perform studies for future development.

Prof. Dr. Ken-ichi Fujita
Guest Editor

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Keywords

  • catalytic chemistry of iridium complexes
  • stoichiometric reactivity of iridium complexes
  • new iridium complexes with unusual structure
  • luminescent complexes of iridium
  • commercial applications of iridium complexes

Published Papers (6 papers)

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Research

Article
Synthesis of Anthraquinones by Iridium-Catalyzed [2 + 2 + 2] Cycloaddition of a 1,2-Bis(propiolyl)benzene Derivative with Alkynes
Inorganics 2019, 7(11), 138; https://doi.org/10.3390/inorganics7110138 - 18 Nov 2019
Cited by 2 | Viewed by 1027
Abstract
[2 + 2 + 2] cycloaddition of a 1,2-bis(propiolyl)benzene derivative with terminal and internal alkynes takes place in the presence of [Ir(cod)Cl]2 (cod = 1,5-cyclooctadiene) combined with bis(diphenylphosphino)ethane (DPPE) to give anthraquinones in 42% to 93% yields with a simple experimental procedure. [...] Read more.
[2 + 2 + 2] cycloaddition of a 1,2-bis(propiolyl)benzene derivative with terminal and internal alkynes takes place in the presence of [Ir(cod)Cl]2 (cod = 1,5-cyclooctadiene) combined with bis(diphenylphosphino)ethane (DPPE) to give anthraquinones in 42% to 93% yields with a simple experimental procedure. A fluorenone derivative can also be synthesized by iridium-catalyzed [2 + 2 + 2] cycloaddition of a benzene-linked ketodiyne with an internal alkyne to give a 94% yield. Full article
(This article belongs to the Special Issue Iridium Complexes)
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Communication
Synthesis of a Half-Sandwich Hydroxidoiridium(III) Complex Bearing a Nonprotic N-Sulfonyldiamine Ligand and Its Transformations Triggered by the Brønsted Basicity
Inorganics 2019, 7(10), 125; https://doi.org/10.3390/inorganics7100125 - 17 Oct 2019
Viewed by 1491
Abstract
Synthesis and reactivities of a new mononuclear hydroxidoiridium(III) complex with a pentamethylcyclopentadienyl (Cp*) ligand are reported. The hydroxido ligand was introduced into an iridium complex having a nonprotic amine chelate derived from N-mesyl-N’,N’-dimethylethylenediamine by substitution of the chloride [...] Read more.
Synthesis and reactivities of a new mononuclear hydroxidoiridium(III) complex with a pentamethylcyclopentadienyl (Cp*) ligand are reported. The hydroxido ligand was introduced into an iridium complex having a nonprotic amine chelate derived from N-mesyl-N’,N’-dimethylethylenediamine by substitution of the chloride ligand using KOH. The resulting hydroxidoiridium complex was characterized by NMR spectroscopy, elemental analysis, and X-ray crystallography. The hydroxido complex was able to deprotonate benzamide and acetonitrile, and showed an ability to accept a hydride from 2-propanol to generate the corresponding hydrido complex quantitatively. In the reaction with mandelonitrile, a cyanide anion was transferred to the iridium center in preference to the hydride transfer. The cyanidoiridium complex was also identified in the reaction with acetone cyanohydrin, and could serve as catalyst species in the transfer hydrocyanation of benzaldehyde. Full article
(This article belongs to the Special Issue Iridium Complexes)
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Article
Successive Activation of C–H and C–O Bonds of Vinyl Ethers by a Diphosphine and Hydrido-Bridged Diiridium Complex
Inorganics 2019, 7(10), 121; https://doi.org/10.3390/inorganics7100121 - 03 Oct 2019
Cited by 1 | Viewed by 1116
Abstract
The reaction of [(Cp*Ir)2(μ-dmpm)(μ-H)][OTf] (2) [Cp* = η5-C5Me5, dmpm = bis(dimethylphosphino)methane] with 2,3-dihydrofuran gives [(Cp*IrH)2(μ-dmpm){μ-(2,3-dihydrofuranyl)}][OTf] (3) in an isolated yield of 70% via the C–H bond activation at the 5-position of 2,3-dihydrofuran. Complex [...] Read more.
The reaction of [(Cp*Ir)2(μ-dmpm)(μ-H)][OTf] (2) [Cp* = η5-C5Me5, dmpm = bis(dimethylphosphino)methane] with 2,3-dihydrofuran gives [(Cp*IrH)2(μ-dmpm){μ-(2,3-dihydrofuranyl)}][OTf] (3) in an isolated yield of 70% via the C–H bond activation at the 5-position of 2,3-dihydrofuran. Complex 3 is slowly converted into [(Cp*Ir)2(μ-dmpm)(μ-C=C(H)CH2CH2OH)][OTf] (4) quantitatively via the proton-mediated C–O bond activation. The reaction of 2 with ethyl vinyl ether gives [(Cp*Ir)2(μ-dmpm)(μ-CH=CH2)][OTf] (5) in the isolated yield of 64% via the successive activation of C–H and C–O bonds. Full article
(This article belongs to the Special Issue Iridium Complexes)
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Communication
Ir-Catalyzed Reduction of Carbonyl Compounds Using Biogenetic Alcohols
Inorganics 2019, 7(9), 114; https://doi.org/10.3390/inorganics7090114 - 12 Sep 2019
Cited by 2 | Viewed by 1230
Abstract
Biomass has gained great attention as an alternative to fuel-derived chemicals. This report concerns new catalytic systems consisting of [IrCp*Cl2]2 (Cp*: Pentamethylcyclopentadienyl) for the reduction of aldehyde and biogenetic alcohols as hydrogen sources. [IrCp*Cl2]2 has been used [...] Read more.
Biomass has gained great attention as an alternative to fuel-derived chemicals. This report concerns new catalytic systems consisting of [IrCp*Cl2]2 (Cp*: Pentamethylcyclopentadienyl) for the reduction of aldehyde and biogenetic alcohols as hydrogen sources. [IrCp*Cl2]2 has been used as a transfer hydrogenation catalyst using fossil fuel-derived alcohols as hydrogen sources in the presence of a base. In contrast, our system does not require any base, and the reaction can proceed in water. Various types of biogenetic alcohols can be used as hydrogen sources, such as monosaccharides, oligosaccharides, and glycerol. Aromatic and aliphatic aldehydes, as well as ketones, were successfully reduced to the corresponding alcohols in the present system. Full article
(This article belongs to the Special Issue Iridium Complexes)
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Communication
Iridium Catalyzed Synthesis of Tetrahydro-1H-Indoles by Dehydrogenative Condensation
Inorganics 2019, 7(8), 97; https://doi.org/10.3390/inorganics7080097 - 06 Aug 2019
Cited by 3 | Viewed by 1250
Abstract
Novel synthetic routes to the commonly encountered indole motif are highly sought after. Tetrahydro-1H-indoles were synthesized for the first time from secondary alcohols and 2-aminocyclohexanol in the presence of a well-established iridium catalyst using a modified synthetic procedure recently developed for [...] Read more.
Novel synthetic routes to the commonly encountered indole motif are highly sought after. Tetrahydro-1H-indoles were synthesized for the first time from secondary alcohols and 2-aminocyclohexanol in the presence of a well-established iridium catalyst using a modified synthetic procedure recently developed for the synthesis of hydrocarbazoles. The catalyst is stabilized by an inexpensive and easy-to-synthesize triazine based PN5P pincer ligand. The reaction proceeds through acceptorless dehydrogenative condensation (ADC) and yields the title compound, dihydrogen, and water and can thus be classified as sustainable synthesis. Overall, five examples, three of which were previously unknown compounds, were prepared. The propitious isolated yields and the mild reaction conditions show the synthetic value of this approach. These tetrahydroindoles can be quantitatively dehydrogenated over a heterogeneous Pd catalyst to yield the corresponding indoles. Full article
(This article belongs to the Special Issue Iridium Complexes)
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Article
Cyclometalated Iridium(III) Complexes Containing Benzoxazole Derivatives and Different Ancillary Ligands for Catalytic Oxidation of Toluene
Inorganics 2018, 6(4), 118; https://doi.org/10.3390/inorganics6040118 - 29 Oct 2018
Cited by 4 | Viewed by 1679
Abstract
A series of cyclometalated iridium(III) complexes that have the general formula [(C^N)2Ir(NR)(X)] (C^N = monoanionic bidentate cyclometalating ligands; NR = pyridine derivatives; X = Cl or I) are designed, prepared, and applied for the transformation of toluene to [...] Read more.
A series of cyclometalated iridium(III) complexes that have the general formula [(C^N)2Ir(NR)(X)] (C^N = monoanionic bidentate cyclometalating ligands; NR = pyridine derivatives; X = Cl or I) are designed, prepared, and applied for the transformation of toluene to benzaldehyde using a clean, highly efficient, and environmentally-friendly process. The activation energies that are needed for the catalytic oxidation of toluene when using these complexes as catalysts are quite low: between 22.9 and 30.8 kcal mol−1. The catalytic frequencies (TOF) are fairly high (up to 7.0 × 102 h−1) with excellent reliability, and the turnover number (TON) can reach 4.2 × 103 after 6 h of processing time. Catalytic tests, X-ray absorption near-edge structure (XANES), and kinetic modeling are used to derive detailed insights into the characteristics of the catalysts and their effects on the reactions that are featured in the catalytic oxidation of toluene. Full article
(This article belongs to the Special Issue Iridium Complexes)
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