Presence Of Transition Metal Compounds Research Articles

Oxidative desulfurization of diesel fraction with hydrogen peroxide in the presence of catalysts based on transition metals

The oxidative desulfurization of a straight-run, nonhydrotreated diesel fraction (boiling range 178–342°C) containing benzothiophene, dibenzothiophene, their alkyl-substituted derivatives, and thioxanthene by the action of hydrogen peroxide in the presence of transition metal compounds (Na2MoO4, Na2WO4, NaVO3, WO3, tungstic acid, and heteropoly tungstate/molybdate H3PMo6W6O40) in a biphasic system followed by the extraction of the oxidation products with dimethylformamide has been studied. The oxidation of the hydrocarbon fraction in the presence of heteropoly tungstate/molybdate under biphasic conditions provides for the removal of up to 82% of total sulfur.

Effect of Transition Metal Compounds on Amorphous SiC Removal Rates

We show here that transition metal compounds when used as additives to silica dispersions enhance a-SiC removal rates (RRs). Silica slurries containing KMnO4 gave RRs as high as 2000 nm h−1 at pH 4. Addition of CuSO4 to this slurry further enhanced the RRs to ∼3500 nm h−1 at pH 6. Furthermore, addition of a low concentration of 250 ppm Brij-35 to this slurry suppressed the RRs of SiO2 to zero, while retaining the RRs of a-SiC at ∼2700 nm h−1, a combination of RRs that is appropriate for hard mask polishing. The underlying mechanisms causing the enhancement in the RRs of a-SiC in the presence of transition metal compounds is discussed based on the RR data and XPS analysis of post-polished wafer surfaces. It is shown that a mixed redox system consisting of the oxidation of a-SiC by KMnO4 enhanced by the catalytic activity of the Cu(II) salt is responsible for the rapid oxidation of a-SiC and the observed enhancement in polish rate with silica based slurries. The adsorption characteristics of Brij-35 on the oxide and carbide surfaces are described based on thermogravimetry data and in achieving the desired polish rate selectivity.

Influence of additives in the batch on benzopyrene emission during the production of anodic carbon and graphite

The influence of various additives to the initial batch on benzopyrene emissions is investigated, both in the production of self-sintering anodes and in the formation of green anodes for graphite production. Benzopyrene is bound in the presence of transition-metal compounds at 600–1000°C.

Three characteristic reactions of alkynes with metal compounds in organic synthesis

AbstractAlkynes have two sets of mutually orthogonal π‐bonds that are different from the π‐bonds of alkenes. These π‐bonds are able to bond with transition metal compounds. Alkynes easily bond with the various kinds of compounds having a π‐bond such as carbon monoxide, alkenes, other alkynes and nitriles in the presence of the transition metal compounds. The most representative reaction of alkynes is called the Pauson–Khand reaction. The Pauson–Khand reactions include the cyclization of alkynes with alkenes and carbon monoxide in the presence of cobalt carbonyls. Similar Pauson–Khand reactions also proceed in the presence of other transition metal compounds. These reactions are the first type of characteristic reaction of alkynes. Other various kinds of cyclizations with alkynes also proceed in the presence of the transition metal compounds. These reactions are the second type of characteristic reaction of alkynes. These include cyclooligomerizations and cycloadditions. The cyclooligomerizations include mainly cyclotrimerizations and cyclotetramerizations, and the cycloadditions are [2 + 2], [2 + 2 + 1], [2 + 2 + 2], [3 + 2], [4 + 2], etc., type cycloadditions. Alkynes are fairly reactive because of the high s character of their σ‐bonds. Therefore, simple coupling reactions with alkynes also proceed besides the cyclizations. The coupling reactions are the third type of characteristic reactions of alkynes in the presence of, mainly, the transition metal compounds. These reactions include carbonylations, dioxycarbonylations, Sonogashira reactions, coupling reactions with aldehydes, ketones, alkynes, alkenes and allyl compounds. Copyright © 2008 John Wiley & Sons, Ltd.

The charge percolation mechanism and simulation of Ziegler-Natta polymerizations, Part VII: Effects of the distribution of chromium active centers on silica on the polymerization of ethylene

The charge percolation mechanism (CPM) of olefin polymerization in the presence of transition metal compounds has been applied to explain the polymerization of ethylene by silica supported chromium oxide. In the previous work of this series, the fundamental issues and mechanism of this polymeri?zation were presented. In this work the compatibility of the CPM with the em?pirical findings is confirmed. The CPM has been applied to explain: the appea?rance of an induction period; the deactivation of active centers and the forma?tion of oligomers; the effects of chromium concentration on the silica surface, the silica surface discontinuity and the pore size of silica on polymerization and the formation of the structure of polyethylene. A mathematical model has been derived to explain the effects of the CrOx/SiO2 ratio on the productivity of Phil?lips catalysts in the polymerization of ethylene. The empirical findings have also been confirmed by computer simulations.

Amination of benzene and toluene with hydroxylamine in the presence of transition metal redox catalysts

The amination of benzene and toluene to aniline and toluidines with hydroxylamine sulfate has been investigated in water–acetic acid and water–acetic acid–sulfuric acid media in the presence of transition metal compounds as catalysts. The process yields are strongly dependent on the temperature, added sulfuric acid and the composition of catalyst. For the amination of benzene, the soluble catalysts, NaVO 3 and Fe(III) salts produce high yields of aniline without addition of H 2SO 4, whereas Na 2MoO 4 and FeSO 4 exhibit substantial activity only in 5 M H 2SO 4. Amination is accompanied by a disproportionation of hydroxylamine catalyzed by the redox active transition metal ions. The favorable effect of H 2SO 4 on the amination is due mostly to the greater stability of hydroxylamine in the strongly acidic medium. Mixed oxides containing V(V) and Mo(VI) are active amination catalysts when suspended in 5 M solution of H 2SO 4 in acetic acid. Introduction of metallic Pd into these oxide catalysts improves performance increasing the yield and selectivity of amination with respect to the aromatic substrate. Toluene exhibited a close to benzene reactivity in amination giving approximately equal yields of o-, m-, p-toluidines. Mechanistic considerations based on literature data and results of ab initio quantum mechanics calculations suggest that the aminating species is the protonated amino radical ⋅NH 3 +, which in the rate-determining step reacts with benzene and toluene to yield the corresponding aminocyclohexadienyl and aminomethylcyclohexadienyl radical intermediates. These are then oxidatively aromatized to give, respectively, aniline and a non-regiospecific mixture of toluidines.

Low-temperature hydrodechlorination of 2,3-dichlorodibenzo-p-dioxin and chlorobenzene with hydrides catalyzed by transition metal compounds

Hydrodechlorination of chlorobcnzene by chemically bound hydrogen in the presence of transition metal compounds was studied. Alkali and alkaline earth metal hydrides (NaH, MgH2, LiAlH4, NaH(LiAlH4)/12) were used as the sources of the chemically bound hydrogen. The effect of the natures of the hydride and of the transition metal on the activity was studied under comparable conditions. The Pd/C-NaH(LiAlH41/2 catalytic system was found to be the most active. This system made it possible to perform the quantitative dechlorination of 2,3-dichlorodibenzo-p-dioxin at 70 °C.

ChemInform Abstract: A Simple Synthesis of 1‐Aminophosphonic Acids from 1‐ Hydroxyiminophosphonates with NaBH4 in the Presence of Transition Metal Compounds.

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 simple synthesis of 1-aminophosphonic acids from 1-hydroxyiminophosphonates with NaBH 4 in the presence of transition metal compounds

A new procedure has been developed for the synthesis of 1-aminophosphonic acids. Diethyl phosphonates are converted to hydroxyiminophosphonates when treated with hydroxylamine hydrochloride. Reduction of hydroxyiminophosphonates with NaBH 4 in MeOH in the presence of MoO 3 or NiCl 2 and hydrolysis of 1- aminophosphonates gave 1-aminophosphonic acids in good yield.

Carbonylation of acetaldehyde in the presence of transition metal compounds

The carbonylation of acetaldehyde to give butyl lactate has been carried out in the presence of rhodium and cobalt compounds atP CO=5–9 MPa andT=383–483 K.

Formation of alkyl peroxides in oxidation of alkanes by H2O2 catalyzed by transition metal complexes

Some reactions between alkanes and H2O2 in the presence of transition metal compounds, e.g. Cr(VI), V(V), Mn(III), Pd(II), Fe(II), yield alkyl hydroperoxides as main products.

Catalyst and solvent effects on the synthesis of acetic acid from methyl formate

Methyl formate can be catalytically converted to acetic acid in the presence of transition metal compounds under carbon monoxide pressure. The nature of the metal catalyst, the promoter and the solvent are determining. Palladium and cobalt compounds associated with lithium iodide are the most efficient catalysts provided that the reaction is carried out in N-methylpyrrolidone under an adequate CO pressure.

Oxidation of saturated hydrocarbons by tert-butyl hydroperoxide in the presence of transition metal compounds

1. The acetylacetonates of V(III), V(IV), Cr(III), and Co(II), the stearates and caproates of Cu(II), Mn(II), Fe(II), and Co(II), and the carbonyl derivatives of Cr, Mn, and Rh catalyze the selective oxidation of nonane, cyclohexane, and diphenylmethane by tert-butyl hydroperoxide to the isomeric ketones. 2. tert-Butoxyl radicals do not take part in the oxidation of hydrocarbons.

Inhibited oxidation of polydimethylsiloxane in the presence of transition metal compounds

The oxidation of polydimethylsiloxane oligomer, “liquid PMS-300” at 285–315°C in the presence of oxidation inhibitors, namely basic ferric caproate and the organosiloxy vanadates has been studied. The main kinetic features of the PMS-300 inhibited oxidation can be explained on the basis of a branched chain oxidation model. The inhibition capacity of the ferric caproate has been found to be used up by the oxidation and longer duration of inhibition is due to the low critical concentrations and to low rates of initiation of the polydimethylsiloxane oxidation.

Polymerisation of pentadienyl compounds in the presence of transition-metal compounds: the polymorphic compound deca-1,3,7,9-tetraenediiron hexacarbonyl

The reaction between Fe(CO) 5 and penta-1,4-dien-3-ol gives two forms of di(pentadienyliron tricarbonyl).

ChemInform Abstract: KINETICS AND MECHANISM OF THE DECOMPOSITION OF ORGANIC HYDROPEROXIDES IN THE PRESENCE OF TRANSITION METAL COMPOUNDS

Chemischer InformationsdienstVolume 7, Issue 6 Preparative Organic Chemistry ChemInform Abstract: KINETICS AND MECHANISM OF THE DECOMPOSITION OF ORGANIC HYDROPEROXIDES IN THE PRESENCE OF TRANSITION METAL COMPOUNDS I. P. SKIBIDA, I. P. SKIBIDASearch for more papers by this author I. P. SKIBIDA, I. P. SKIBIDASearch for more papers by this author First published: February 10, 1976 https://doi.org/10.1002/chin.197606070AboutPDF 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 onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume7, Issue6February 10, 1976 RelatedInformation

The reactions of organometallic compounds of transition metals with molecular nitrogen and carbon dioxide

A development of organometallic chemistry has revealed wide possibilities for activating various unsaturated and saturated molecules for numerous novel reactions. Many nitrogen fixating systems based on the low-valent transition metal derivatives and reducing agents have been discovered. Depending on the reaction conditions, complexed nitrogen reduction occurs to form either hydrazine derivatives or ammonia. An investigation of the nitrogen fixating systems involving Lewis acids, to regenerate the catalyst, has led to catalytic nitrogen fixation. Nitrogen activated by complex formation with transition metal compounds is capable of insertion reactions into metal—carbon bonds to form organic amines. In this connection the possibility arises of forming amines from the reaction of nitrogen with hydrocarbons in the presence of transition metal compounds. Transition metal nitrogen compounds seem to be intermediates in the 'reverse' reactions as well, i.e. decompositions of nitrogencompounds with nitrogen evolution (Sandmeyer reaction, hydrazine oxidation. etc). Unlike nitrogen, carbon dioxide is rather reactive and undergoes insertion reactions into non-transition metal-carbon boids. Carbon dioxide also appeared to be capable of direct or indirect complex formation with low-valent transition metal compounds (Ru, Rh, Pt, etc.). Investigation of the stability of such complexes permits novel synthetic and catalytic reactions to be found. Thus the formation of Me—H bonds (e.g. in the formic acid decomposition with CO2 evolution) can be utilized for catalytic reduction of olefins and other unsaturated compounds by means of formic acid. When the intermediate carbon dioxide complexes with Me—C bonds (carboxylates) are formed. the competitive reaction occurs, i.e. olefin insertion into Me—H or Me—C bonds with elimination of the respective carboxylic acid. Another interesting reaction, insertion of CO2 into Me—H or Me—C bonds, can follow either 'normal' (formation of a carbon-carbon' bond) or 'reverse' (formation of the metalloacid ester) pathways. A development of organometallic chemistry has provided unusual possibilities for activating various unsaturated and saturated molecules and introducing them into the various reactions. The present lecture deals with the problem of activation by transition 607