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Omae I.,Omae Research Laboratories
Current Organic Chemistry | Year: 2014

Cyclometalation reactions are usually defined as the reactions of metal compounds with conventional substrates, such as benzylamines and 2-phenylpyridines. In contrast, unconventional cyclometalation reactions are the reactions of metal compounds with unconventional base substrates, such as 2-amino-3-picoline, anilines and 2- aminopyridines, and with auxiliary substrates, such as aldehydes and alkynes. Other unconventional cyclometalation reactions also exist, examples include the cyclocarbonylations of metal carbonyl compounds with unsaturated hydrocarbons, such as alkynes, alkenes and aryl compounds; reactions with 2-vinylpyridines; and rollover cyclometalation reactions. © 2014 Bentham Science Publishers.


Omae I.,Omae Research Laboratories
Coordination Chemistry Reviews | Year: 2014

The use of metal compounds as anticancer agents is one of the applications of the five-membered ring products of cyclometalation reactions, including those with Pt, Pd, Rh, Ir, Ru, Os and Au. The coordinating atoms in these anticancer agents are mainly N and, in very few cases, P, S and O. The substrates used for these cyclometalation reactions are mainly pyridine ring compounds, such as 2-phenylpyridines, benzo[. h]quinolines, 2,6-diphenylpyridines and so on. The ancillary ligands used are bipyridines, 1,10-phenathrolines, 2,6-bispyridylpyridine, N-heterocyclic carbenes and so on.The platinum compounds of 2,6-phenylpyridylpyridine CNN pincer N-heterocyclic carbene, the gold compounds of 2,6-diphenylpyridine CNC pincer alkylphosphine or N-heterocarbene, and the osmium compounds of 2-phenylpyridine, phenyloxazole, m-bispyridylbenzenes cyclometalated 1,10-phenanthrolines or 2,6-bispyridylpyridines show very high cytotoxicity values compared to those of cisplatin. © 2014 Elsevier B.V.


Omae I.,Omae Research Laboratories
Journal of Organometallic Chemistry | Year: 2011

Cyclometalation reactions proceed very easily with one step reaction between metal compounds and substrates having a heteroatom such as O, S, N, P and As. However, under mild reaction conditions, many agostic compounds which are intermediates in these cyclometalation reactions, can be isolated. The metal compounds used for the formation of these agostic intermediates are both transition metal and main group metal compounds. The substrates are nitrogen-containing compounds, phosphorus-containing compounds, oxygen-containing compounds and sulfur-containing compounds. These agostic intermediates are mainly δ-C-H agostic compounds, some are γ-C-H agostic compounds and very few are ε-C-H-agostic compounds. The agostic intermediates are prepared, usually, under mild reaction conditions in the cyclometalation reaction. These agostic compounds are also prepared from cyclometalation reaction products, e.g., by the protonation, irradiation, and elimination of ligand molecules by vacuum, inert gas current, dehydration with a molecular sieves 4A, etc. Some agostic compounds are utilized for preparation of stable catalysts, e.g., hydrogenation catalysts. © 2010 Elsevier B.V. All rights reserved.


Omae I.,Omae Research Laboratories
Coordination Chemistry Reviews | Year: 2016

Organic light-emitting diodes (OLEDs) are manufactured primarily by synthesizing five-membered ring products using cyclometalation reactions. Highly photoluminescent quantum efficient emitters are primarily prepared by utilizing the following five types of iridium compounds: 1. N-Heterocyclic carbene compounds such as phenylimidazolinate-type carbene compounds and 2-phenylpyridine N-heterocyclic carbene compounds; 2. NCN-tridentate type compounds; 3. Polycyclic compounds, such as phenanthro-imidazole and fluorenylpyrazole compounds; 4. Heterocyclic compounds, such as 2-phenylpyridines, 2-phenylpyridine fluorinated compounds, phenyl-imidazole, -pyrazole, and -triazole compounds, 2,3'-bispyridines and phosphites; and 5. High-molecular-weight cyclometalated compounds such as the dendrimers of phenyltriazoles.In particular, the presence of a high field ligand such as an N-heterocyclic carbene in these compounds facilitates high energy emission, which results in the desired blue-colored light required for OLED applications. © 2015 Elsevier B.V.


Omae I.,Omae Research Laboratories
Current Organic Chemistry | Year: 2016

In carbon dioxide utilization by cyclometalated five-membered ring products, the following compounds are used in four types of applications: 1. 2-Phenylpyrazole iridium compounds, pincer phosphine iridium compounds and 2-phenylimidazoline iridium compounds are used as catalysts for both formic acid production from CO2and H2, and hydrogen production from the formic acid. This formic acid can be a useful agent for H2 production and storage for fuel cell electric vehicles. 2. Other chemicals, e.g., dimethyl carbonate, methane, methanol and CO, are produced with dimethylaminomethylphenyltin compounds, pincer phosphine iridium compounds, pincer phosphine nickel compound and ruthenium carbene compound or 2-phenylpyridine iridium compounds, and phenylbenzothiazole iridium compounds as the catalysts for the reactions with CO2. 3. The five-membered ring intermediates of cyclometalation reactions with the conventional substrates react with carbon dioxide to afford their many types of carboxylic acid derivatives. 4. Carbon dioxide is easily immobilized at room temperature with immobilizing agents such as pincer phosphine nickel compounds, pincer phosphine palladium compounds, pincer N,N-dimethylaminomethyltin compounds and tris(2-pyridylthio)methane zinc compounds. © 2016 Bentham Science Publishers.


Omae I.,Omae Research Laboratories
Coordination Chemistry Reviews | Year: 2012

Highly thermodynamically stable carbon dioxide is now used industrially as a feedstock for the carboxylation of four types of reactive substrates. The first category comprises oxygen-containing compounds, namely epoxides and alcohols. The reactions of reactive epoxides easily proceed at high yields in the presence of various kinds of transition metal compounds, non-transition metal compounds and organic compounds. However, the reactions of alcohols proceed at high yields only in the presence of a Bu 2Sn(OMe) 2 catalyst when dehydrating agents shift the equilibrium toward products without serious damage of catalysts by water by forming ladder compounds. The second category involves nitrogen-containing compounds, where urea is the dominant industrial product. Carbon-carbon unsaturated compounds such as aryl compounds, alkynes and alkenes comprise the third category of substrates. The carboxylations of these substrates in the presence of metal compounds such as Cu, Ni and Pd generate the corresponding carboxylic acid derivatives. The five-membered compounds of the cyclometalated substrates can generate the corresponding carboxylic compounds using lithium, rhodium, nickel and palladium compounds as catalysts. The fourth substrate is hydrogen. We expect that the production of formic acid and methanol using hydrogen by utilizing natural energy generation such as geothermal energy and wind power will grow because these products will be in great demand in the near future. © 2012 Elsevier B.V.


Omae I.,Omae Research Laboratories
Journal of Organometallic Chemistry | Year: 2016

Some organometallic compounds, especially five-membered ring products of cyclometalation reactions, can be utilized as sensing materials in sensors for detecting materials of interest, such as gases; metal ions; halogens; cyanic compounds; sugars; glycoproteins, including lectins and avidins; explosives; and DNA. The compounds used for the detection of the presence of materials are often cyclometalated five-membered ring compounds. These compounds comprise metallic elements, mostly iridium and platinum compounds, and substrate moieties, such as 2-phenylpyridines, 2-phenylbenzothazoles and 2-phenylqunolines. Commonly used ancillary ligands include acetyl acetonate (acac), bipyridines and 1,10-phenanthrolines. Detection by sensors is performed by watching the color changes of the emissions and the increased emission intensity or by quenching emission intensity of the compounds used for detection. The reactions of the cyclometalated compounds with the materials to be detected are usually reversible, so the sensors can be repeatedly used for detection. © 2016 Elsevier B.V.


Omae I.,Omae Research Laboratories
Applied Organometallic Chemistry | Year: 2010

Carbonyl group-containing organometallic intramolecular-coordination five-membered ringcompounds are easily synthesized by the following five reaction methods: (1) cyclometalation, especially, orthometalation reactions; (2) the reactions of the moieties of an unsaturated carbon-carbon bond attached to a carbonyl group (C≡C-CO, C=C-CO); (3) the reactions of an unsaturated carbon-carbon bond with carbon monoxide (C≡C and CO, C=C and CO); (4) carbonylative ring expansion reactions; and (5) others. These compounds are very easily and regio-specifically synthesized with many kinds of metal compounds, including both transition metals and main group metals. Many of such the reactions are easily applied to organic syntheses. Copyright ©2010 John Wiley & Sons, Ltd.

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