Showing papers on "Osmium published in 1993"

Ruthenium and osmium metal carbene complexes for olefin metathesis polymerization

Abstract: Processes for the synthesis of several new carbene compounds of ruthenium and osmium are provided. These novel complexes function as stable, well-defined catalysts for the metathesis polymerization of cyclic olefins.

Cyclopropanation catalyzed by osmium porphyrin complexes

Abstract: The authors report herein the use of osmium porphyrins as stereoselective cyclopropanation catalysts using ethyl diazoacetate with a variety of alkenes. In addition, their studies show that an isolable carbene complex ((TTP)Os[double bond]CHCO[sub 2]Et) is capable of catalytically and stoichiometrically cyclopropanating styrene. Several significant aspects have evolved from the use of osmium meso-tetra-p-tolyporphyrin complexes as catalysts for the cyclopropanation of a variety of alkenes by ethyl diazoacetate. This system provides the highest anti/syn isomer ratio reported to date (a/s = 10) for the catalytic cyclopropanation of styrene by ethyl diazoacetate. Unlike typical cyclopropanation catalysts which produce cyclopropenes from alkyne substrates, the osmium porphyrin catalysts generate bicyclobutanes from phenylacetylene. Moreover, the authors have isolated, on preparative scale, the first carbene complex, (TTP)Os[double bond]CHCO[sub 2]Et, that is catalytically active toward cyclopropanation. The fact that this carbene complex can stoichiometrically cyclopropanate styrene with the same stereoselectivity as in the catalytic process is further evidence for it as an important species in the catalytic cycle. 12 refs., 1 tab.

A Convenient, Mild Method for Oxidative Cleavage of Alkenes with Jones Reagent/Osmium Tetraoxide

Abstract: Oxidative scission of alkenes is used for preparation of carboxylic acids and ketones. The authors present a method for cleavage of terminal olefins to yield a carboxylic acid based on the realization that a catalytic amount of osmium tetraoxide chromate should convert an olefin via a diol to an acid and/or ketone. The authors believe that and the osmium is then reoxidized by the chromate, which also cleaves the 1,2-diol. 1 tab.

Osmium tetrafluoride dioxide, cis-OsO2F4

Abstract: The new osmium(VIII) oxo fluoride obtained from the reaction of KrF 2 and OsO 4 in anhydrous HF solution and originally identifed as OsOF 6 is shown by quantitative material balance, electron diffraction, NMR and vibrational spectroscopy, and density functional theory calculations to be cis-OsO 2 F 4 . The combined electron diffraction study and DFT calculations result in the following geometry: r Os=0 =1.674(4) A, r Os-Fe =1.883(3) A, r Os-Fe =1.843(3) A, O=Os-O=103.5(25) o , F e -Os-F e =77.3(26) o , F a -Os-F a =172.0(3) o , O-Os-F a = 92.4(17) o

Process for forming a semiconductor device having a reducing/oxidizing conductive material

Abstract: The present invention includes a semiconductor device having a layer including an elemental metal and its conductive metal oxide, wherein the layer is capable being oxidized or reduced preferentially to an adjacent region of the device. The present invention also includes processes for forming the devices. Substrate regions, silicon-containing layers, dielectric layers, electrodes, barrier layers, contact and via plugs, interconnects, and ferroelectric capacitors may be protected by and/or formed with the layer. Examples of elemental metals and their conductive metal oxides that may be used with the present invention are: ruthenium and ruthenium dioxide, rhenium and rhenium dioxide, iridium and iridium dioxide, osmium and osmium tetraoxide, or the like.

Oxidative addition of methyl iodide to monosubstituted and disubstituted derivatives of osmium pentacarbonyl

Abstract: Oxidative addition at room temperature of CH 3 I to Os(CO) 4 L or Os(CO) 3 L 2 (L=PMe 3 ) gives complexes [Os(CO) 4 -LCH 3 ]I (3) or [Os(CO) 3 L 2 CH 3 ]I (5), respectively. Complexes 3 and 5 react at higher temperature (50-70 o C) to give complexes Os(CO) 3 LCH 3 I (7) and Os(CO) 2 L 2 CH 3 I (9), respectively. If this reaction is carried out in chloride-containing solvents, the formation of Os(CO) 3 L(CH 3 )Cl and Os(CO) 2 L 2 (CH 3 )Cl is also oberved.

Mono- and dinuclear complexes of ruthenium(II) and osmium(II) with a 3,5-bis(2-pyridyl)-1,2,4-triazole cyclohexyl-bridged spacer. Absorption spectra, luminescence properties, and electrochemical behavior

Abstract: Two novel dinuclear complexes of Ru(II) and Os(II) with a bis-chelating bridging ligand based on 3,5-bis(2-pyridyl)-1,2,4-triazole moieties have been synthesized, and their absorption spectra, electrochemical behavior, and luminescence properties have been studied. For comparison purposes, the parent mono-chelating ligand and its mononuclear complexes have also been synthesized and their properties have been studied.

Mercaptide complexes of osmium porphyrins. Structure of Os(TTP)(SC6F4H)2

Abstract: Aryl mercaptans RSH (R=p-tolyl, C 6 F 4 , C 6 F 5 , 2,6-Me 2 C 6 H 3 ) react with dioxoosmium(VI) porphyrins [porphyrin =mes-tetra-p-tolylporphyrin (TTP), octaethylporphyrin (OEP)] to give diamagnetic osmium(IV) derivatives which contain two mercaptide ligands. When sterically encumbered mercaptans and porphyrins are utilized, an Os(III) mercaptide complex results. Osmium(III) porphyrin mercaptide complexes can also be prepared either by pyridine-promoted reductive elimination of disulfide from Os(TTP)(SR) 2 or by treating the metal-metal-bonded dimer [Os 2 (TTP) 2 ] 2+ with mercaptan/pyridine mixtures

New synthetic routes to [M3(CO)9(µ3-η2:η2:η2-C6H6)](M = Ru or Os)

Abstract: A new, more convenient route to the benzene cluster [Ru3(CO)9(µ3-η2:η2:η2-C6H6)] directly from [Ru3(CO)12] has been established. Triruthenium dodecacarbonyl, [Ru3(CO)12], undergoes reaction with Me3NO–CH2Cl2 in the presence of cyclohexa-1,3-diene to give the clusters [Ru3H(CO)9(C6H7)] and [Ru3(CO)9(µ3-η2:η2:η2-C6H6)] in moderate yield. Triosmium dodecacarbonyl does not react similarly, but from the reaction of [Os3(CO)10(MeCN)2] with cyclohexa-1,3-diene a key intermediate compound [Os3(CO)10(η4-C6H8)] has been isolated and the solid-state structure of its acetonitrile solvate established by single crystal X-ray diffraction analysis at 150 K. The structure is monoclinic, space group P21/n, with a= 8.932(8), b= 17.387(13), c= 14.833(15)A, β= 105.69(6)° and Z= 4. The three osmium atoms form a regular triangle with a mean Os–Os distance of 2.877(12)A. Two osmium atoms, Os(1) and Os(2), are co-ordinated to four carbonyl ligands and one, Os(3), co-ordinates to two carbonyl ligands. All carbonyl ligands are terminal and approximately linear. The cyclohexadiene ligand is η4 co-ordinated to Os(3)via the 1,3-diene moiety, donating four electrons in total. On thermolysis, this compound is converted to [Os3H(CO)9(C6H7)] and then eventually to [Os3(CO)9(µ3-η2:η2:η2-C6H6)] by established means.

Platinum Group Elements

Abstract: Platinum group elements are ruthenium, rhodium and palladium (of similar weight as, but lighter than silver, the next element in the periodic table by atomic number) and osmium, iridium and platinum (of similar weight as, but lighter than gold, the next element in the periodic table by atomic number). As opposed to gold and silver, known probably since the stone age, the first certain discovery of platinum, in the alluvial deposits of the Rio Pinto – Columbia, is as recent as 1741. Platinum was introduced to Europe by Sir Charles Wood who brought it to England during that same year. Osmium and iridium were isolated together from the residues of platinum ores in aqua regia in 1803 or 1804 by English chemist Smithson Tennant. The existence of rhodium and palladium was established in 1803 by English doctor W. Hyde Wollaston. Ruthenium was recognized as an element in 1844 or 1845 by Russian chemist C.E. Claus.

Mechanism of oxidative dehydrogenation of an amine coordinated to osmium(II)

Abstract: The synthesis and characterization of [Os( bpy )2( ampy )]2+{ bpy = 2,2′-bipyridine; ampy = 2-( aminomethyl )pyridine} have been studied, together with its irreversible two-electron oxidative dehydrogenation to the corresponding osmium(II) imine species in aqueous solution, by utilizing electrochemical and stopped-flow kinetic techniques. The kinetic data were analysed by using numerical integration methods to obtain solutions for the differential equations derived from mechanistic proposals. The results were consistent with the initial oxidation of the metal centre to OsIII and the intermediacy of a deprotonated OsIV species, formed by disproportionation, in the subsequent ligand dehydrogenation.

Osmium LIII edge extended X-ray absorption fine-structure studies on the osmium(VIII) oxide-fluorides, OsO3F2,K[OsO3F3] and Cs2[OsO4F2]

Abstract: Osmium LIII edge extended X-ray absorption fine-structure data have been obtained for the title compounds and refined to give, for OsO3F2, d(OsO)1.70 A and d(OsF)  1.89 and 2.09 A, for K[OsO3F3], d(OsO)1.70 A and d(OsF)1.92 A and, for Cs2[OsO4F2], d(OsO)  1.70 A and d(OsF)  2.05 A (bond lengths accurate to ±0.02 A).

Synthesis of 5,15-Diaryl-Substituted Oxochlorins from 5,15-Diaryloctaethylporphyrin

Abstract: 5,15-Diaryl-substituted oxochlorins were prepared from osmium tetraoxide oxidation of 5,15-diaryloctaethylporphyrin followed by acid-catalyzed pinacol rearrangement. Optical and electrochemical properties of this macrocyclic ring are studied by measuring the absorption and fluorescence spectra, fluorescence lifetimes, and one-electron oxidation and reduction potentials.