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Journal ArticleDOI

Ruthenium-catalyzed oxygenation of saturated hydrocarbons by t-butylhydroperoxide

01 Dec 1992-Journal of Molecular Catalysis (Elsevier)-Vol. 77, Iss: 3, pp 283-288
TL;DR: In this paper, a free-radical mechanism appears to dominate when TBHP is employed, thus accounting for the remarkably high rates of alkane conversions (up to ca. 8 turnovers per minute).
About: This article is published in Journal of Molecular Catalysis.The article was published on 1992-12-01. It has received 53 citations till now. The article focuses on the topics: Cyclooctane & Hypochlorite.
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Journal ArticleDOI
TL;DR: In this article, it was shown that the same alkylhydridoplatinum(IV) complex is the intermediate in the reaction of ethane with platinum(II) σ-complexes.
Abstract: ion. The oxidative addition mechanism was originally proposed22i because of the lack of a strong rate dependence on polar factors and on the acidity of the medium. Later, however, the electrophilic substitution mechanism also was proposed. Recently, the oxidative addition mechanism was confirmed by investigations into the decomposition and protonolysis of alkylplatinum complexes, which are the reverse of alkane activation. There are two routes which operate in the decomposition of the dimethylplatinum(IV) complex Cs2Pt(CH3)2Cl4. The first route leads to chloride-induced reductive elimination and produces methyl chloride and methane. The second route leads to the formation of ethane. There is strong kinetic evidence that the ethane is produced by the decomposition of an ethylhydridoplatinum(IV) complex formed from the initial dimethylplatinum(IV) complex. In D2O-DCl, the ethane which is formed contains several D atoms and has practically the same multiple exchange parameter and distribution as does an ethane which has undergone platinum(II)-catalyzed H-D exchange with D2O. Moreover, ethyl chloride is formed competitively with H-D exchange in the presence of platinum(IV). From the principle of microscopic reversibility it follows that the same ethylhydridoplatinum(IV) complex is the intermediate in the reaction of ethane with platinum(II). Important results were obtained by Labinger and Bercaw62c in the investigation of the protonolysis mechanism of several alkylplatinum(II) complexes at low temperatures. These reactions are important because they could model the microscopic reverse of C-H activation by platinum(II) complexes. Alkylhydridoplatinum(IV) complexes were observed as intermediates in certain cases, such as when the complex (tmeda)Pt(CH2Ph)Cl or (tmeda)PtMe2 (tmeda ) N,N,N′,N′-tetramethylenediamine) was treated with HCl in CD2Cl2 or CD3OD, respectively. In some cases H-D exchange took place between the methyl groups on platinum and the, CD3OD prior to methane loss. On the basis of the kinetic results, a common mechanism was proposed to operate in all the reactions: (1) protonation of Pt(II) to generate an alkylhydridoplatinum(IV) intermediate, (2) dissociation of solvent or chloride to generate a cationic, fivecoordinate platinum(IV) species, (3) reductive C-H bond formation, producing a platinum(II) alkane σ-complex, and (4) loss of the alkane either through an associative or dissociative substitution pathway. These results implicate the presence of both alkane σ-complexes and alkylhydridoplatinum(IV) complexes as intermediates in the Pt(II)-induced C-H activation reactions. Thus, the first step in the alkane activation reaction is formation of a σ-complex with the alkane, which then undergoes oxidative addition to produce an alkylhydrido complex. Reversible interconversion of these intermediates, together with reversible deprotonation of the alkylhydridoplatinum(IV) complexes, leads to multiple H-D exchange

2,505 citations

Journal ArticleDOI
TL;DR: In this paper, a thorough discussion of homogeneous catalysis by transition metal oxygen anion clusters (polyoxometalates), with a focus on mechanism, is provided, and a general compilation of the reactions, including catalytic electrooxidations or electroreductions, reported to date is given.

1,331 citations

Journal ArticleDOI
TL;DR: In this article, the most interesting systems for the cyclohexane synthesis with different oxidants such as hydrogen peroxide, tert -butyl hydroperoxide and molecular oxygen were reviewed.
Abstract: Many efforts have been made to develop new catalysts to oxidize cyclohexane under mild conditions. Herein, we review the most interesting systems for this process with different oxidants such as hydrogen peroxide, tert -butyl hydroperoxide and molecular oxygen. Using H 2 O 2 , Na-GeX has been shown to be a most stable and active catalyst. Mesoporous TS-1 and Ti-MCM-41 are also stable, but the use of other metals such as Cr, V, Fe and Mo leads to leaching of the metal. Homogeneous systems based on binuclear manganese(IV) complexes have also been shown to be interesting. When t -BuOOH is used, the active systems are those phthalocyanines based on Ru, Co and Cu and polyoxometalates of dinuclear ruthenium and palladium. Microporous metallosilicates containing different transition metals showed leaching of the metal during the reactions. Molecular oxygen can be used directly as an oxidant and decreases the leaching of active species in comparison to hydrogen peroxide and tert -butyl hydroperoxide. Metal aluminophosphates (metal: Mn, Fe, Co, Cu, Cr V) are active and relatively stable under such conditions. Mn-AlPO-36 yields directly adipic acid, but large amounts of carboxylic acids should be avoided, as they cause metal leaching from the catalysts. Rare earth exchanged zeolite Y also shows good selectivity and activity. In the last part of the review, novel alternative strategies for the production of cyclohexanol and cyclohexanone and the direct synthesis of adipic acid are discussed.

585 citations

Journal ArticleDOI
TL;DR: The focus of this Review is on complexes that should, in principle, exist as discrete molecular species in solution, and which are therefore of interest for their reactivity, their future synthetic utility and potential applications, for example, in catalysis or nanoscience.
Abstract: Polyoxometalates containing noble metal ions, such as ruthenium, osmium, rhodium, palladium, platinum, silver and gold, are a structurally diverse class of compounds. They include both classical heteropolyanions (vanadates, molybdates, tungstates) in which noble metals are present as heteroatoms, as well as the recently discovered class of polyoxometalates with noble metal "addenda" atoms. The focus of this Review is on complexes that should, in principle, exist as discrete molecular species in solution, and which are therefore of interest for their reactivity, their future synthetic utility and potential applications, for example, in catalysis or nanoscience.

339 citations

References
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Journal ArticleDOI
TL;DR: A simple preparation of dichlorotetrakis(dimethyl sulphoxide) ruthenium(II) is given in this paper, where the i.m.r and 1H n.r. spectra indicate mixed sulphur and oxygen co-ordination sites.
Abstract: A simple preparation of dichlorotetrakis(dimethyl sulphoxide)ruthenium(II) is given. The i.r. and 1H n.m.r. spectra of the complex suggest there are mixed sulphur and oxygen co-ordination sites. The complex is a useful starting material for other ruthenium(II) complexes.

569 citations

Journal ArticleDOI
TL;DR: Le dioxo(tetramesitylporphyrinato) ruthenium(VI) catalyse l'epoxydation des olefines (cyclooctene, cis-and trans-β-methylstyrene, norbornene) a temperature and pression ambiantes
Abstract: Le dioxo(tetramesitylporphyrinato) ruthenium(VI) catalyse l'epoxydation des olefines (cyclooctene, cis- et trans-β-methylstyrene, norbornene) a temperature et pression ambiantes

394 citations

Journal ArticleDOI
TL;DR: In this paper, the chemistry of halogen-dimethyl sulfoxide-ruthenium(II) complexes with the general formula RuX/sub 2/(DMSO)/sub 4/ (X = Cl, Br) is reported.
Abstract: The chemistry of halogen-dimethyl sulfoxide-ruthenium(II) complexes with the general formula RuX/sub 2/(DMSO)/sub 4/ (X = Cl, Br) is reported. In particular the synthesis and x-ray structure of trans-RuCl/sub 2/(DMSO)/sub 4/ are described and compared with those of the already known cis-RuCl/sub 2/(DMSO)/sub 4/ and trans-RuBr/sub 2/(DMSO)/sub 4/. The structure op a new crystal form of cis-RuCl/sub 2/(DMSO)/sub 4/ is also reported. While the cis isomers are thermodynamically more stable and form from the trans species a photochemically driven cis to trans isomerization reaction is observed in dimethyl sulfoxide solution. Kinetic parameters for the thermal trans to cis isomerization reactions for trans-RuCl/sub 2/(DMSO)/sub 4/ and trans-RuBr/sub 2/(DMSO)/sub 4/ are reported. In chloroform solution the complexes, and in particular the trans isomers, tend to release a dimethyl sulfoxide molecule to give pentacoordinated Ru(II) complexes. However, in aqueous solution, while the cis complexes immediately release one DMSO, the trans ones release two. In both cases, this step is followed by the slow dissociation of a halide ion. For the chloro derivatives the dissociation is completely inhibited at physiological chloride concentrations. Preliminary results from pharmacological tests show that trans-RuCl/sub 2/(CMSO)/sub 4/ is more active than the cis isomer against Lewis lung carcinoma, a metastasizingmore » murine tumor. A remarkable dependence of activity on the halogen nature (Cl > Br) is also observed. 33 refs., 4 figs., 9 tabs.« less

301 citations

Journal ArticleDOI
TL;DR: In this article, the rate constants for carboxylates in water at 24.3/sup 0/C, k = 12.2 +/- 1.2, 3.4 +/- 0.3, and 0.026 +/- 0.003 M/sup -1/ s/sup 1/s/sup 2 +/ for isopropylbenzene.
Abstract: The kinetics of oxidation of p-/sup -/O/sub 2/CC/sub 6/H/sub 4/CH(CH/sub 3/)/sub 2/,p-/sup -/O/sub 2/CC/sub 6/H/sub 4/CH/sub 2/CH/sub 3/,and p-/sup -/O/sub 2/CC/sub 6/H/sub 4/CH/sub 3/ by Ru(trpy)(bpy)O/sup 2 +/ (trpy is 2,2',2''-terpyridine; bpy is 2,2'-bipyridine) to the corresponding ..cap alpha.. alcohols in water and of C/sub 6/H/sub 5/CH(CH/sub 3/)/sub 2/ and C/sub 6/H/sub 5/CH/sub 3/ by Ru(bpy)/sub 2/(py)O/sup 2 +/ in acetonitrile have been studied. The following conclusions are drawn from kinetics data obtained spectrophotometrically: (1) Rate constants increase with increasing alkyl substitution; for the carboxylates in water at 24.3/sup 0/C, k = 12.2 +/- 1.2, 3.4 +/- 0.3, and 0.43 +/- 0.04 M/sup -1/ s/sup -1/ in the order shown above. (2) Rate constants decrease dramatically for the reactions in acetonitrile; k(24.3/sup 0/C) = 0.026 +/- 0.003 M/sup -1/ s/sup -1/ for isopropylbenzene. (3) In water, rate constants are independent of added O/sub 2/ or of changes in ionic strength. (4) In acetonitrile the added nucleophiles water, tert-butyl alcohol, or bromide ion enter the rate law directly in terms first order in added nucleophile. From the temperature dependence of k for the oxidation of p-/sup -/O/sub 2/CC/sub 6/H/sub 4/CH(CH/sub 3/)/sub 2/, ..delta..H/sup + +/ = 7 +/- 1 kcal/mol andmore » ..delta..S/sup + +/ = -32 +/- 4 eu. It is concluded that the redox step for the reactions involves a two-electron, hydride ion transfer step. The reactions occur by a template mechanism in that oxo group transfer from Ru to the substrate does not occur and the added oxygen atom must come from the solvent, p-/sup -/O/sub 2/CC/sub 6/H/sub 4/CH(CH/sub 3/)/sub 2/ (-H:/sup -/; +H/sub 2/O) ..-->.. p-/sup -/O/sub 2/CC/sub 6/H/sub 4/C(OH)(CH/sub 3/)/sub 2/. The solvent or added nucleophile (in acetonitrile) is directly involved in the redox step, apparently by assisting the loss of the hydride ion by electron pair donation.« less

159 citations