Cobalt Complex Catalysts Research Articles

Covalantly bonded Schiff base cobalt complex catalyst for the selective oxidation of linear alkanes using molecular oxygen

Graphic A Schiff base [1,2-bis(salicylidene amino)-phenylene] cobalt complex catalyst bonded on carbamate modified silica gel has been prepared for one step liquid-phase oxidation of alkanes with molecular oxygen. At moderate temperatures (150 °C) and low oxygen pressure (16 atm), the oxidation of n -hexane and n -heptane were studied. In the case of n -hexane, it was found that isomerization, dehydrocyclization as well as oxidation products both were formed, while for n -heptane, there was no cracking or reforming reaction and the oxidation products are principally 4-heptanone, 2-heptanone, 2-heptanol and heptanoic acid. For n -hexane, if the reaction is carried out in nitrogen atmosphere, only isomerization and dehydrocyclization products are formed in high yield (∼74.0%) with no 2,2-dimethyl butane (2,2-DMB) and 2,3-dimethyl butane (2,3-DMB). It is thus seen that the catalyst reported in this work can also be used for reforming of n -hexane and requires much lower temperature. The thermogravimetric analysis (TGA) analysis shows that it is stable up to 211 °C and the atomic absorption spectroscopy (AAS) shows a negligible loss of metal in 50 h use of the catalyst upto 180 °C reaction temperature.

ChemInform Abstract: Highly Enantioselective Cyclopropanation of Styrenes and Diazoacetates Catalyzed by 3‐Oxobutylideneaminatocobalt(II) Complexes. Part 1. Designs of Cobalt Complex Catalysts and the Effects of Donating Ligands.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

P-Cresol autoxidation using CoAPO-5 prepared by microwave heating of the precursor gel: comparison with homogeneous and biphasic reaction schemes using cobalt salt or complex catalysts

p-Cresol autoxidation to p-hydroxybenzaldehyde was performed at 60 °C and atmospheric pressure, using three methods: (1) quasi-heterogeneous reaction using CoAPO-5 catalyst; (2) homogeneous reaction using CoBr 2 salt; and (3) biphasic organic–aqueous interfacial reaction using cobalt complexes together with a surfactant. Cobalt was proven to be the most active/selective for the p-hydroxybenzaldehyde synthesis among the transition metal salts tested. Highly crystalline and uniform CoAPO-5 was prepared using microwave heating in 40 min from the precursor gels and characterized using XRD, SEM, and UV–VIS spectroscopy. p-Cresol conversion and selectivity to p-hydroxybenzaldehyde increase with the cobalt contents and improved as the Co/ p-cresol (mg/g) ratio increases to ca. 1.0. The oxygen selectivity was 82–85% for CoAPO-5, which is slightly higher than obtained with CoBr 2. The highly alkaline solution employed for the reaction, however, resulted in serious metal leaching. The biphasic reaction attempted for p-cresol autoxidation resulted in poor performance due to the limits in solvent selection. The performance of p-cresol autoxidation reaction was strongly governed by the solvent and followed the order methanol>ethanol>butanol, all miscible with water. Hardly any reaction took place in non-polar solvents such as chloroform or toluene, or in 2-ethyl-1-hexanol.

Dynamic Kinetic Resolution with Enantioselective Borohydride Reduction Catalyzed by Optically Active β-Ketoiminato Cobalt(II) Complexes: Highly Diastereo- and Enantioselective Preparation of Optically Active anti-Aldol Compounds

Abstract Optically active anti-2-alkyl-3-hydroxy esters were stereoselectively obtained from the corresponding 2-alkyl-3-keto esters using enantioselective borohydride reduction along with dynamic kinetic resolution in the presence of optically active β-ketoiminato cobalt complex catalysts. The reduction system provided an alternative preparation for anti-aldol compounds with high diastereo- and enantioselectivities.

Highly Enantioselective Cyclopropanation of Styrenes and Diazoacetates Catalyzed by 3-Oxobutylideneaminatocobalt(II) Complexes, Part 1. Designs of Cobalt Complex Catalysts and the Effects of Donating Ligands

Abstract Highly enantioselective cyclopropanation of styrene derivatives and diazoacetates was effectively catalyzed by reasonably designed 3-oxobutylideneaminatocobalt(II) complexes, whose ligands were prepared from 1,2-dimesitylethylenediamine and alkyl 3-oxobutanoates. The steric demand of the diamine unit of the complexes seriously influenced the enantioselectivity, and the ester groups on their side chains somewhat improved the trans-selectivity. Addition of a catalytic amount of N-methylimidazole significantly accelerated the reaction and enhanced the enantioselectivity due to its coordination to the center cobalt atom of the complex as an axial ligand. Alcoholic or aqueous alcoholic solvents were also effective particularly for the cyclopropanation of 1-substituted 1-phenylethylenes to achieve high enantioselectivity in aqueous methanol.

Highly chemo-, diastereo-, and enantioselective reduction of 1,2-dialkyl-3-aryl-1,3-diketones for preparation of aldol-type compounds.

[reaction: see text]. Highly chemo-, diastereo-, and enantioselective borohydride reduction of 2-substituted-1,3-diketones was achieved in the presence of the optically active beta-ketoiminato cobalt complex catalysts to afford the optically active 2-substituted-3-hydroxyketones. The present catalytic and enantioselective reduction could provide an alternative potential for preparation of optically active anti-aldol-type compounds.

Reductive desymmetrization of 2-alkyl-1,3-diketones catalyzed by optically active beta-ketoiminato cobalt complexes.

[reaction: see text] The reductive desymmetrization of acyclic 1,3-diketones was achieved for the first time by catalytic borohydride reduction in the presence of optically active beta-ketoiminato cobalt(II) complex catalysts. In this reaction, various 2-substituted-1,3-diaryl-1,3-propanediones were converted into the corresponding optically active 2-substituted-1,3-diaryl-3-hydroxypropanone in good-to-high yields with excellent diastereo- and enantioselectivities and high catalytic efficiencies.

後周期遷移金属錯体触媒によるオレフィン重合 最近の研究動向

This review summarizes the recent developments in the field of olefin polymerization, especially focuses on the topic by nickel, palladium, iron, cobalt, and ruthenium complex catalysts including the brief summary of this research background. A lot of studies have been explored concerning olefin polymerization by nickel and palladium complex catalysts especially after the discovery of α-diimine coordinated nickel and palladium catalysts reported by Brookhart et al., and these results introduce new possibilities for making new type of olefin-based copolymers by these catalysts. In particular, recent discovery concerning ethylene polymerization by iron and cobalt complexes containing 2, 6-bis (imino) pyridine ligand attracted particular attention due to the exceptionally high catalytic activity, and the contents concerning this topic have also been summarized briefly. We also wish to introduce our recent results concerning olefin polymerization by ruthenium and iron complexes-cocatalyst systems.

Optically Active Aldiminato Cobalt(II) Complex Catalyst for Enantioselective Hetero Diels-Alder Reaction

Optically Active Aldiminato Cobalt(II) Complex Catalyst for Enantioselective Hetero Diels-Alder Reaction

Highly Enantioselective Cyclopropanation of Styrenes with Diazoacetates Catalyzed by Optically Active β-Ketoiminato Cobalt(II) Complexes

Abstract The highly enantioselective cyclopropanation of styrenes with diazoacetates was achieved using reasonably designed β-ketoiminato cobalt(II) complex catalysts. In the presence of optically active cobalt(II) complexes derived from optically active 1,2-(2,4,6-trimethylphenyl)-1,2-ethylenediamine, the cyclopropanation of styrene with methyl, ethyl, and tert-butyl diazoacetates proceeded to afford the corresponding cyclopropanecarboxylates with 94-96% ee.

Optically active β-ketoiminato cobalt(II) complexes as highly efficient catalysts in enantioselective borohydride reduction of ketones, imines, and α,β-unsaturated carboxylates

A new class of cobalt complexes with optically active N, N′-ethylenebisketoiminato ligands was synthesized, and one of them was fully characterized by X-ray crystallographic analysis. These cobalt(II) complexes proved to be efficient catalysts in enantioselective borohydride reduction of aryl ketones, phosphinyl imines, and β,β-disubstituted α,β-unsaturated carboxylates. It was found that the enantiofacial discrimination in the borohydride reduction was influenced by the structure of the diphenylethylenediamine moiety of the cobalt complex catalysts.

ChemInform Abstract: Enantioselective Borohydride 1,4‐Reduction of α,β‐Unsaturated Carboxamides Using Optically Active Cobalt(II) Complex Catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A Comparative Study of Organic Cobalt Complex Catalysts for Oxygen Reduction in Polymer Electrolyte Fuel Cells

Reduction of platinum catalysts loading is a central issue in polymer electrolyte fuel cells. As alternatives for platinum, some organic metal chelate compounds are tested as cathode catalysts, such as cobalt aza-complexes or cobalt complexes possessing aminophenyl moieties featured as Co-N4 or Co-N2O2 chelate structures. The way of immobilization of catalysts on the graphite surface influences their stability as well as the performance of oxygen reduction. Heat-treated catalysts supported on graphite at 600°C show much better oxygen reduction abilities than as-received metal complexes. The original chemical structure of metal complexes affects crucially the catalytic ability, though initial structures of molecules are no more intact after the heat treatment. The catalytic activity of these complexes may originate from the central chelate unit CoN4 on the carbon substrate, and this unit is assumed to constitute the basic coordination site for an oxygen molecule. Electropolymerized catalysts impart a high level of oxygen reduction ability, probably due to the improved molecular orientation for oxygen coordination and formation of good chelate sites on the graphite surface.

Enantioselective Borohydride 1,4-Reduction of α, β-Unsaturated Carboxamides Using Optically Active Cobalt(II) Complex Catalysts

Abstract The enantioselective borohydride reduction catalyzed by cobalt(II) complex was successfully applied to 1,4-reduction of β,β-disubstituted α,β-unsaturated carboxamides. In the presence of less than 1 mol% of optically active aldiminato cobalt(II) complex catalyst, the corresponding carboxamides were obtained in high yields with high enantiomeric excesses.

Oxidation studies of phenols with cobalt(II) ion-modified silica in a liquid chromatographic reactor

The activity of cobalt(II) ion-modified silica, a new catalyst for the oxidation of phenols with dissolved oxygen in organic solvents, has been studied in liquid chromatographic reactors using several approaches. In this reactor mode, catalyst activity can be maintained over months of repeated use while phenols are oxidized to p-benzoquinones at or below 45 °C. This approach eliminates problems of catalyst separations. Using the ideal liquid chromatographic reactor model with inert standard methods, the reaction is found to be first-order with respect to the phenolic reactants. Some pseudo-first-order rate constants have also been measured. The cobalt(II) ions bonded to silica probably function through reaction pathways similar to those of homogeneous cobalt complex catalysts for phenol oxidations. However, they are stable for long periods of time under the mild reaction conditions used here and can provide separation with concerted reaction.

ChemInform Abstract: Enantioselective Borohydride Reduction of N‐Diphenylphosphinyl Imines Using Optically Active Cobalt(II) Complex Catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Enantioselective Borohydride Reduction of N-Diphenylphosphinyl Imines Using Optically Active Cobalt(II) Complex Catalysts

Abstract The enantioselective borohydride reduction using optically active cobalt(II) complex catalysts was successfully applied to various aryl N-diphenylphosphinyl imines, and the corresponding reduced products were obtained in good yields with high enantiomeric excesses (up to 99% ee). The optically active primary amines were obtained by the successive hydrolysis under mild conditions.

Practical and Efficient Enantioselective Borohydride Reduction of Aromatic Ketones Catalyzed by Optically Active Cobalt(II) Complexes Using Pre-Modified Borohydride

Abstract A catalytic enantioselective borohydride reduction of aromatic ketones in presence of 0.1-1 mol% of optically active aldiminato cobalt(II) complex catalysts at 0 °C was successfully achieved using precisely pre-modified borohydride with one equivalent each of tetrahydrofurfuryl alcohol, ethanol and NaBH4. The corresponding secondary alcohols were produced in less than 45 min with high enantiomeric excesses (up to 98% ee). The above method was successfully applied to kinetic and dynamic kinetic resolutions of aromatic ketones.

Aerobic Epoxidation of Olefins Catalyzed by Cobalt(II) Complex Using Propionaldehyde Diethyl Acetal as a Reductant

Abstract In the presence of bis(3-methyl-2,4-pentanedionato)cobalt(II) complex catalyst, various trisubstituted olefins are smoothly monooxygenated into the corresponding epoxides in high yields under neutral conditions by the combined use of molecular oxygen and propionaldehyde diethyl acetal.

ChemInform Abstract: Novel Method for Oxidation of Secondary Alcohols (I) into Ketones (II) with Molecular Oxygen by Using a Cobalt(II) Complex Catalyst.

ChemInformVolume 20, Issue 42 Preparative Organic Chemistry ChemInform Abstract: Novel Method for Oxidation of Secondary Alcohols (I) into Ketones (II) with Molecular Oxygen by Using a Cobalt(II) Complex Catalyst. T. YAMADA, T. YAMADA Basic Res. Lab. Org. Synth., Mitsui Petrochem. Ind., Ltd., Nagaura, Chiba 299-02, JapanSearch for more papers by this authorT. MUKAIYAMA, T. MUKAIYAMA Basic Res. Lab. Org. Synth., Mitsui Petrochem. Ind., Ltd., Nagaura, Chiba 299-02, JapanSearch for more papers by this author T. YAMADA, T. YAMADA Basic Res. Lab. Org. Synth., Mitsui Petrochem. Ind., Ltd., Nagaura, Chiba 299-02, JapanSearch for more papers by this authorT. MUKAIYAMA, T. MUKAIYAMA Basic Res. Lab. Org. Synth., Mitsui Petrochem. Ind., Ltd., Nagaura, Chiba 299-02, JapanSearch for more papers by this author First published: October 17, 1989 https://doi.org/10.1002/chin.198942079AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume20, Issue42October 17, 1989 RelatedInformation