Showing papers on "Osmium published in 1998"
TL;DR: By converting the ions generated in an electrochemical half-cell reaction to a fluorescence signal, the most active compositions in a large electrode array have been identified.
Abstract: Combinatorial screening of electrochemical catalysts by current-voltage methods can be unwieldy for large sample sizes. By converting the ions generated in an electrochemical half-cell reaction to a fluorescence signal, the most active compositions in a large electrode array have been identified. A fluorescent acid-base indicator was used to image high concentrations of hydrogen ions, which were generated in the electrooxidation of methanol. A 645-member electrode array containing five elements (platinum, ruthenium, osmium, iridium, and rhodium), 80 binary, 280 ternary, and 280 quaternary combinations was screened to identify the most active regions of phase space. Subsequent “zoom” screens pinpointed several very active compositions, some in ternary and quaternary regions that were bounded by rather inactive binaries. The best catalyst, platinum(44)/ruthenium(41)/osmium(10)/iridium(5) (numbers in parentheses are atomic percent), was significantly more active than platinum(50)/ruthenium(50) in a direct methanol fuel cell operating at 60°C, even though the latter catalyst had about twice the surface area of the former.
904 citations
TL;DR: A. Lanthanum, Yttrium, and Scandium 2126 B. Hafnium, Zirconium and Titanium 2126 C. Tantalum, Niobium, and Vanadium 2127 D. Tungsten, Molybdenum, and Chromium 2127 E. Osmium, Ruthenium, iron, and iron 2128 1. Osmylation 2128 2. Reactions with Zerovalent Compounds 2131 3. Redox Reactions 2134 5.
Abstract: A. Lanthanum, Yttrium, and Scandium 2126 B. Hafnium, Zirconium, and Titanium 2126 C. Tantalum, Niobium, and Vanadium 2127 D. Tungsten, Molybdenum, and Chromium 2127 E. Rhenium, Technetium, and Manganese 2128 F. Osmium, Ruthenium, and Iron 2128 1. Osmylation 2128 2. Reactions with Zerovalent Compounds 2131 3. Other Addition Reactions 2133 4. Redox Reactions 2134 5. Cocrystallizations 2134 G. Iridium, Rhodium, and Cobalt 2135 1. Adduct Formation with Vaska-Type Complexes, Ir(CO)Cl(PR3)2 2135
440 citations
TL;DR: In this article, two depth profiles of the osmium concentration and the187Os/186Os isotopic ratio in the Indian Ocean were obtained from an experimental method that eliminated the problems related to Osmium preconcentration.
Abstract: Two depth profiles of the osmium concentration and the187Os/186Os isotopic ratio in the Indian Ocean showed that the osmium concentration seems to be unaltered by chemical or biological processes occuring in seawater; accordingly, osmium is conservative. These data were obtained from an experimental method that eliminated the problems related to osmium preconcentration. This method led to a new evaluation of the concentration of osmium in seawater; the mean concentration of osmium and the187Os/186Os ratio are equal to 10.86 ± 0.07 picograms per kilogram and 8.80 ± 0.07, respectively. The results suggest the existence of an organocomplex that dominates the speciation of osmium in seawater.
177 citations
132 citations
TL;DR: The osmium tetroxide-mediated dihydroxylation of meso-tetraphenylporphyrin leads to the formation of the vic-diol 2,3-vic -diol-2,3 -chlorin this article.
Abstract: The osmium tetroxide-mediated dihydroxylation of meso-tetraphenylporphyrin leads to the formation of the vic-diol meso-tetraphenyl-2,3-vic-diol-2,3-chlorin. The corresponding Ni(II) complex was con...
92 citations
TL;DR: The dithiolate-bridged complexes [M2(μ-bdt)(CO)6] (M = Fe (1), Ru (2), Os (3); bdt = benzene-1,2-dithiolates) have been prepared and X-ray diffraction studies reveal that although the three compounds have analogous molecular structures their crystal structures are different as a result of different molecular packings as discussed by the authors.
82 citations
TL;DR: In this article, two redox-active osmium complexes of the type (Os(bpy)2Cl(pyX))+ have been synthesized, where pyX corresponds to a pyridine derivative bearing a functional group (aldehyde, carboxylate).
78 citations
TL;DR: In this article, it was shown that the unsaturated five-coordinate MCl2(CHMe)(PH3)2 is more stable than the saturated hexacoordinate MCl 2H(CMe)2 for Ru, while the two species are almost isoenergetic in the case of Os; computationally, it was found that the osmium hydrido carbyne involves a large activation energy (27.2 kcal/mol) to transform unimolecularly to its carbene isomer.
76 citations
TL;DR: In this paper, the authors synthesized and characterized via single-crystal X-ray diffraction methods iron(II), ruthenium (II), and osmium(II) carbonyl derivatives of (1-methylimidazole)(5,10,15,20,20-tetraphenylporphyri...
Abstract: We have synthesized and characterized via single-crystal X-ray diffraction methods iron(II), ruthenium(II), and osmium(II) carbonyl derivatives of (1-methylimidazole)(5,10,15,20-tetraphenylporphyri...
68 citations
TL;DR: In this paper, the first reported example of osmium and ruthenium/osmium metals linked across a 1,4-dioxolene bridge is described, where M is Os or Ru and bpy is 2,2-bipyridyl.
Abstract: The extent of metal−ligand orbital mixing and the degree of electronic coupling between [M(bpy)2]2+ fragments linked through a redox active 1,4-dihydroxy-2,5-bis(pyrazol-1‘-yl)benzene (p-L) bridge is described, where M is Os or Ru and bpy is 2,2‘-bipyridyl. This is the first reported example of osmium and ruthenium/osmium metals linked across a 1,4-dioxolene bridge. In fast scan cyclic voltammetry, the redox processes are reversible and four distinct one-electron processes are observed for the bridge and metal centers in the homo- and hetero-dinuclear complexes. The potential at which the first oxidation step occurs does not depend on the identity of the metal center. UV/vis spectroelectrochemistry, together with resonance Raman spectroscopy, suggests that the first two oxidation steps occur on the bridging ligand. For all complexes, an orbital mixing gradient occurs; metal−ligand orbital mixing increases in the order HQ ≪ SQ < Q (HQ is the reduced hydroquinone bridge, SQ the semiquinone, and Q the quinon...
66 citations
Patent•
19 Nov 1998TL;DR: The Schiff base derivatives of the ruthenium and osmium carbene catalysts show unexpectedly improved thermal stability while maintaining high metathesis activity, even in polar protic solvents as mentioned in this paper.
Abstract: The present invention generally relates to ruthenium and osmium carbene catalysts for use in olefin metathesis reactions. More particularly, the present invention relates to Schiff base derivatives of ruthenium and osmium carbene catalysts and methods for makig the same. The inventive catalyst are generally prepared by the treatment of unmodified catalysts with the salts of the desired Schiff base ligands, in which an anionic and a neutral electron donating ligands of the unmodified catalysts are simultaneously replaced. The Schiff base derivatives of the ruthenium and osmium carbene catalysts show unexpectedly improved thermal stability while maintaining high metathesis activity, even in polar protic solvents. Although the inventive catalysts may be used in all metathesis reactions, use of these catalysts for ring-closing metathesis ("RCM") reactions is particularly preferred.
TL;DR: When arylboranes react with the osmium(VI) nitrido complex [HB(pz)3}Os(N)Cl2], they do not just bind to the nitrogen atom.
Abstract: When arylboranes react with the osmium(VI) nitrido complex [{HB(pz)3}Os(N)Cl2], they do not just bind to the nitrogen atom. A B−C bond is cleaved, and the phenyl and boryl units are separately bound to nitrogen in the product (e.g. 1; X=Ph; Y=Ph, OBPh2). Subsequent hydrolysis leads to cleavage of the B−N bond and generation of the anilido species [{HB(pz)3}Os(NHPh)Cl2]. pz=pyrazolyl.
Patent•
05 May 1998TL;DR: In this article, an alkali resistant supported catalyst is proposed for the preparation of carboxylic acid salts, which is useful in the synthesis of acid acid salts and is composed of a plurality of metal particles selected from the group consisting of osmium, iridium, rhodium and a coating of a catalytically active metal.
Abstract: Supported catalyst useful in the preparation of carboxylic acid salts, said catalyst comprising; an alkali resistant support, a plurality of metal particles selected from the group consisting of osmium, iridium and rhodium and a coating of a catalytically active metal selected from the group of copper, cobalt, nickel, cadmium or mixtures thereof
TL;DR: Treatment of Os(Bcat)Cl(CO)(PPh3)2 (1; Bcat = B-1,2-O2C6H4) with AgSbF6 in THF removes chloride and gives a cationic boryl complex formulated as [Os(BCat)(CO)(THF)2(PPh 3)2] SbF 6].
TL;DR: A variety of reactions occur between trans-[OsVI(tpy)(Cl)2(N)]+ (1) (tpy = 2,2‘:6‘,2,2 ‘‘-terpyridine) and N3-.
Abstract: A variety of reactions occur between trans-[OsVI(tpy)(Cl)2(N)]+ (1) (tpy = 2,2‘:6‘,2‘‘-terpyridine) or [OsVI(tpm)(Cl)2(N)]+ (2) (tpm = tris(1-pyrazolyl)methane) and N3-. The reaction between 2 and ...
TL;DR: A series of nitrido-ruthenium (VI) and -osmium(VI) complexes containing chelating di-, tri- and tetra-anionic ligands was synthesized by ligand substitution reaction in methanol under room conditions in the presence of 2,6-dimethylpyridine as mentioned in this paper.
Abstract: A series of nitrido-ruthenium(VI) and -osmium(VI) complexes containing chelating di-, tri- and tetra-anionic ligands was synthesized by ligand substitution reaction in methanol under room conditions in the presence of 2,6-dimethylpyridine. All the newly prepared complexes are air-stable diamagnetic solids. The crystal structures of seven complexes have been established by X-ray crystallography. The RuN (1.615–1.594 A) and the OsN (1.612–1.621 A) bond distances are rather insensitive to the electron-donating power of the auxiliary ligands. All the nitridoruthenium(VI) complexes react spontaneously with triphenylphosphine, and the intermediate [RuIV(NPPh3)L1(py)Cl] has been isolated and characterized spectroscopically for the reaction with [RuVIN(L1)Cl]. However, for those nitridoruthenium(VI) complexes bearing the tri- (L2)3– and tetra-anionic (L3,4)4– ligands, the phosphiniminatoruthenium(IV) intermediate undergoes further reaction with pyrazole to generate a bis(pyrazole)ruthenium(IV) complex as the product.
TL;DR: In this article, two kinds of new osmium(II) porphyrin oligomers having tetraarylporphyrins with 3-pyridyl and phenyl groups as axial or a bridging ligands, Dimer-Oblique and cis-Trimer Oblique, were synthesized and characterized by spectral methods.
Abstract: Two kinds of new osmium(II) porphyrin oligomers having tetraarylporphyrins with 3-pyridyl and phenyl groups as axial or a bridging ligands, Dimer-Oblique and cis-Trimer-Oblique were synthesized and characterized by spectral methods. In cis-Trimer-Oblique, atropisomerization caused by the rotation of pyridyl groups was observed by 1H NMR spectral measurements at room temperature.
Patent•
20 Jun 1998TL;DR: In this paper, a ruthenium and osmium carbene catalysts with bridged e-donor ligands coordinated on the metal were described, and their preparation and their use for synthesizing polymers, for ring-closing metathesis of olefins and for isomerizing olefs.
Abstract: The invention relates to new ruthenium and osmium carbene catalysts with bridged e- donor ligands coordinated on the metal, to their preparation and to their use for synthesizing polymers, for ring-closing metathesis of olefins and for isomerizing olefins.
Patent•
13 Jun 1998TL;DR: In this paper, a penta-and hexacoordinated ruthenium and osmium carbene catalysts are described, in which a sulfur, oxygen or nitrogen atom is attached to the carbene group which is coordinated with the central RUThenium or Osmium atom, to their preparation and use for synthesizing polymers, for ring-closing metathesis of olefins and for isomerizing olefs.
Abstract: The invention relates to penta- and hexacoordinated ruthenium and osmium carbene catalysts, in which a sulfur, oxygen or nitrogen atom is attached to the carbene group which is coordinated with the central ruthenium or osmium atom, to their preparation and to their use for synthesizing polymers, for ring-closing metathesis of olefins and for isomerizing olefins.
TL;DR: The Os(VI) nitrido complex, TpOs(N)Cl2 (1), acts as a π-acid ligand in the cobalt and platinum complexes CpCo[NOs(Tp)Cl 2]2 (2) and (Me2S)cl2Pt-NOs[Tp]Cl2 [3]2 as mentioned in this paper.
TL;DR: In this article, the 2-arylazo ligands with [Os (bpy)2 (ap-Me)) ClO4 complex has been determined by X-ray crystallography.
TL;DR: In this article, the radiationless transition rate in the excited triplet MLCT states of tris(bipyridine)osmium(II) (Os(bpy)32+; bpy = 2,2'n 2'n −2'biprithm, 2,1'n, 2.2 'n −1' n −2 n 2.
Abstract: The solvent effect on the radiationless transition rates from the excited triplet MLCT (metal-to-ligand charge-transfer) states of tris(bipyridine)osmium(II) (Os(bpy)32+; bpy = 2,2‘-bipyridine) and tris(phenanthroline)osmium(II) (Os(phen)32+; phen = 1,10-phenanthroline) was investigated in water−methanol mixed solvent and its deuterated analogues at various temperatures Similar measurements were carried out in H2O−D2O and H2O−dioxane mixed solvents A significant isotope effect of the solvent on the rate constant of the radiationless relaxation to the ground state was observed in water, while only a small one was recognized in methanol The radiationless transition rate in the H2O−D2O mixture depends linearly on the mole fraction of D2O, while that in the H2O−methanol mixture shows no linear dependence on the mole fraction of methanol Those solvent effects of the radiationless transition are described as the energy transfer from the metal complex to the water molecule included in the Os(II) complex It
Patent•
24 Nov 1998TL;DR: In this paper, the authors introduced penta-and hexa-coordinated ruthenium and osmium complexes with a mono- or bi-cyclic, aromatic heterocyclyl group containing at least one nitrogen atom that is coordinated with the ruthensium or osmias central atom.
Abstract: The invention relates to penta- and hexa-coordinated ruthenium and osmium complexes with a mono- or bi-cyclic, aromatic heterocyclyl group containing at least one nitrogen atom that is coordinated with the ruthenium or osmium central atom. The novel compounds are excellent catalysts for metathesis reactions and the ring-closure of dienes.
TL;DR: Spectroscopic studies of the reaction of [Os3(CO)11MeCN] with para-thiocresol to form [Os 3(µ-H)(CO)10( µ-SC6H4Me-p] indicate that the reaction proceeds via a two-step consecutive process involving the intermediate [Os1( CO)11-(MeC6H 4SH-p)], in which there is an agostic Os-H-S interaction as discussed by the authors.
TL;DR: In this article, the sol-gel process has been used to prepare osmium doped tin oxide thin films and the energy gap and refractive index were evaluated from optical measurements.
Abstract: The sol-gel process has been used to prepare osmium doped tin oxide thin films. The energy gap and refractive index were evaluated from optical measurements. Electrical characterization has been performed in a controlled atmosphere in order to investigate the influence of methane on the electrical conductance. New results have been obtained that make tin oxide doped with osmium a very interesting material for fabrication of low power consumption sensors for methane detection.
TL;DR: In this article, the reaction involving iridium(IV) takes place through intermediate formation of free radicals in a MeCO2Na-MeCO2H buffer medium, whereas a one-step two-electron transfer process occurs in the oxidations by OsVIII and PtIV in an alkaline medium.
Abstract: Oxidations of glycolaldehyde (GA) to glyoxal by osmium(VIII), iridium(IV) and platinum(IV) have been investigated in aqueous solution, and the orders with respect to each [reactant] determined. The reaction involving iridium(IV) takes place through intermediate formation of free radicals in a MeCO2Na-MeCO2H buffer medium, whereas a one-step two-electron transfer process occurs in the oxidations by OsVIII and PtIV in an alkaline medium. Mechanisms consistent with the experimental findings are proposed.
TL;DR: It was evident that the osmium conductive metal coating is much more advantageous than the other coatings for obtaining high resolution images on the observations of the fine structures, such as the epidermal basement membrane.
Abstract: Osmium conductive metal coating was performed for the scanning electron microscopic observation of the epidermal basement membrane. An extremely thin osmium coating induced the equivalent electrical conductivity as that of a thick platinum coating. As a result, by this coating, the resolution was only nominally reduced. The meshwork structure of the lamina densa and the three-dimensional morphology of the anchoring fibrils were observed in detail. Scanning electron microscopic observation of the osmium-coated specimen coincided with that of the transmission electron microscopic observations. It was evident that the osmium conductive metal coating is much more advantageous than the other coatings for obtaining high resolution images on the observations of the fine structures, such as the epidermal basement membrane.
TL;DR: In this paper, the four stereomer 1-(4-hydroxy-3-methoxy)-phenyl-1,2,3-propanetriols were obtained in about 30% yields starting from ferulic acid by a synthesis based on osmium catalyzed asymmetric dihydroxylation.