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Anchoring of unimolecular metal oxide onto appropriate supports is a promising and attractive approach for designing efficient metal–oxide-based catalysts from the perspective of economic and environmental sustainability. In the present paper, anchoring of osmium (Os) oxide onto silanol-functionalized polyoxometalates (POMs) to form a single-site supported Os-POM catalyst, in which the isolated osmium tetroxide was tris-grafted on a silanol-functionalized POM platform, has been studied in detail for catalytic oxidation of propylene with dioxygen by using density functional theory (DFT) calculations with the M06L functional. The results derived from the molecular geometry, electronic structure, and OsO bonding feature for this Os-POM catalyst show that (i) rotation of the anionic center subunit of the silanol-functionalized trilacunary POM ligand leads to a coordinated environment conversion from a tetrahedron to a trigonal bipyramid around the transition metal Os center; (ii) a detailed comparison shows that the trigonal bipyramid configuration is the most stable species and provides a large OsO distance and (iii) possesses a matched orbital level for epoxidation of propylene to epoxypropane. The calculated free energy profiles for the epoxidation of propylene show that the rate-determining step is desorption of the first epoxypropane molecule from the Os center. Electronic structure analysis along the reaction pathway shows that the Os-POM catalyst serves as an electrophile, accepting electrons from the propylene π bonding orbital to the π* antibonding orbital of the Os-POM catalyst to break the OsO bond during the oxygen transfer process. Oxygen transfer to the terminal carbon atom of propylene is more favored than the bridging carbon atom because the electron-donating methyl substituent in propylene makes the terminal carbon atom more nucleophilic and accessible for the electrophilic attack by the OsO bond. Cleavage of dioxygen on the Os-POM catalyst is a barrier free process via a quintet-to-singlet state intersystem crossing. The ability of the POM platform to accept and stabilize excess electrons from the Os center effectively promotes the oxygen transfer process, and thus is favorable for epoxidation of propylene by dioxygen.

High-pressure crystal growth and synthesis of selected solid-state osmium oxides, many of which are perovskite-related types, are briefly reviewed, and their magnetic and electrical properties are introduced. Crystals of the osmium oxides, including NaOsO 3 , LiOsO 3 , and Na 2 OsO 4 , were successfully grown under high-pressure and high-temperature conditions at 6 GPa in the presence of an appropriate amount of flux in a belt-type apparatus. The unexpected discovery of a magnetic metal–insulator transition in NaOsO 3 , a ferroelectric-like transition in LiOsO 3 , and high-temperature ferrimagnetism driven by a local structural distortion in Ca 2 FeOsO 6 may represent unique features of the osmium oxides. The high-pressure and high-temperature synthesis and crystal growth has played a central role in the development of solid-state osmium oxides and the elucidation of their magnetic and electronic properties toward possible use in multifunctional devices.

A compositionally new osmium oxide, Ca2InOsO6, which crystallizes in a double-perovskite structure, was synthesized through a high-pressure and high-temperature synthesis method. The crystal structure of Ca2InOsO6 was determined by X-ray diffraction to be monoclinic with the space group P21/n, like other double-perovskite osmium oxides. Magnetic measurements revealed that Ca2InOsO6 is antiferromagnetic below 14K.

The oxidation of ethylene by osmium tetroxide (OsO4), osmyl hydroxide (OsO2(OH)2) and osmyl chloride (OsO2Cl2) have been studied by hybrid density functional theory at the B3LYP/LACVP∗ level of theory. It was found that in the reaction of OsO4 with ethylene, the [3 + 2] addition pathway leading to a five-membered metallacycle intermediate is more favorable than the [2 + 2] addition to form a four-membered metallaoxetane and that the reaction leads ultimately to the formation of diols without epoxide formation, in agreement with earlier works on the subject. The reaction of ethylene with osmyl hydroxide (OsO2(OH)2), which is released when the ‘cyclic’ esters formed from [3 + 2] reaction of OsO4 with ethylene undergo hydrolysis, was found to be less favorable, kinetically and thermodynamically, than the [3 + 2] reaction of OsO4 with ethylene. In the reaction of OsO2Cl2 with ethylene it was found that the [2 + 2] addition pathway to form a four-membered metallacycle is more favorable than the [3 + 2] addition to form the five-membered metallacycle intermediate. It was also found that the formation of an epoxide precursor from the reaction of OsO2Cl2 with ethylene, though possible, is a very unfeasible reaction kinetically and therefore epoxide is not a likely product in the reaction. The results of this study indicates that the preference of the [3 + 2] pathway in the addition of metal oxides across C C bonds, which has been established for osmium tetroxide, is not pervasive in all osmium oxo complexes as publications on the subject seem to suggest.

Dimethyl trisulfide (DMTS) is involved in the unpalatable aroma of stale Japanese sake, called "hineka". Recently, we isolated one of the precursor compounds of DMTS in sake and identified it as 1,2-dihydroxy-5-(methylsulfinyl)pentan-3-one (DMTS-P1), a previously unknown compound. In this work, the contribution of DMTS-P1 to the formation of DMTS was investigated. DMTS-P1 was chemically synthesized from methional in three steps, consisting of the Grignard reaction, followed by oxidation by MnO(2) and an immobilized osmium oxide catalyst. The formation of synthetic DMTS-P1 was confirmed by a comparison of the liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) data to that of natural DMTS-P1. Quantitative analysis of DMTS-P1 in sake was developed using LC-MS/MS, and a positive correlation was observed between the concentration of DMTS-P1 in sake and the production of DMTS during storage. These results indicate that DMTS-P1 contributes to the formation of DMTS in sake.

Na2OsO4 crystals were grown by a NaCl flux method under high pressure. It crystallizes in the Ca2IrO4-type structure without having additional elements or metal vacancies, which are usually accommodated. It appears that Na2OsO4 is a metal-stoichiometric Ca2IrO4-type compound never been synthesized to date. Na2OsO4 has the octahedral environment of Os6+O6 so that the electronic configuration is 5d2, suggesting the magnetic S=1 ground state. However, magnetization, electrical resistivity, and specific heat measurements indicated that the non-magnetic S=0 state is much likely for Na2OsO4 than the S=1 state. Band structure calculations and the structure analysis found that the disagreement is probably due to the statically uniaxial compression of the OsO6 octahedra, resulting in splitting of the t 2 g band.

Stable electroactive mixed films of osmium oxide/hexachloroplatinate, osmium oxide and platinum have been deposited on different electrode materials by cycling the electrode potential repetitively in solution containing Os3+ and PtCl. The film growth of was monitored by using cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM). The cyclic voltammetric features of modified electrode in Os3+ solution resembles that of surface wave, and involves ions-exchange with Os3+ ions present in the solution. Based on the SEM results the modifier was considered as one-dimensional, mixed-valent polymeric film, and stabilized by Os3+/2+ counter ions. Finally, the electrocatalytic activity of the modified electrode was examined toward reduction of NAD+, chloroacetic acids and nitrous oxide.

Osmium tetroxide (OsO4) is a commonly used stain for unsaturated lipids in electron and optical microscopy of cells and tissues. In this work, the localization of osmium oxide and specific lipids was independently monitored in mouse adipose tissue by using time-of-flight secondary ion mass spectrometry with Bi cluster primary ions. Substance-specific ion images recorded after OsO4 staining showed that unsaturated C18 fatty acids were colocalized with osmium oxide, corroborating the view that osmium tetroxide binds to unsaturated lipids. In contrast, saturated fatty acids (C14, C16 and C18) and also unsaturated C16 fatty acids show largely complementary localizations to osmium oxide. Furthermore, the distributions of saturated and unsaturated diglycerides are consistent with the specific binding of osmium oxide to unsaturated C18 fatty acids. The abundance of ions, characteristic of phospholipids and proteins, is strongly decreased as a result of the osmium staining, suggesting that a large fraction of these compounds are removed from the tissue during this step, while ions related to fatty acids, di- and triglycerides remain strong after osmium staining. Ethanol dehydration after osmium staining results in more homogeneous distributions of osmium oxide and unsaturated lipids. This work provides detailed insight into the specific binding of osmium oxide to different lipids.

Samples of Paramecium caudatum are observed by means of a scanning electron microscope (SEM) and a projection X-ray microscope (XRM) with computer tomography (CT) function. The samples are fixed with two kinds of fixatives, glutaraldehyde and osmium-tetra oxide acid. After the fixation and replacement procedure with t-buthyl alcohol, the samples followed by a freeze drying, well retain their structures. Surface structures, cilia and microfibrillar systems including infraciliary lattice structures, are clearly depicted by SEM observation. On the other hand, XRM images give quite different information, namely, in the case of osmium oxide fixation, the structures of internal organelles like the macronucleus placed in the central part of cell body and trichocysts located under the cell membrane of a whole body are visible. In the case of glutaraldehyde fixation, the surface structures and internal structures are both visible but their image contrast is fairly weak. In order to examine toxicological effect, Paramecium caudatum samples treated in the environmental condition containing nano-particles of Ag (17 nm across) and Co-ferrite (300 nm across) are observed with results of certain morphological differences, namely, inner vacuoles increase in number and in volume in Co-ferrite treated cells as compared with Ag treated ones. But then, cilia-less areas increase on the surface of the body of Ag treated cells. In the case of Co-ferrite treated cells, cilia-less areas are not clearly detected. Whether these morphological differences observed in Ag and Co-ferrite treated cells are caused by the differences of materials or particle sizes remain to be examined in future.

Particles of osmium or an inorganic polymeric film of osmium oxide-ruthenium cyanide (OsO-RuCN) electrodeposited on glassy carbon (GC) electrocatalyze the oxidation of dopamine (DA), adrenaline (AD), and noradrenaline (NAD). It is found that these biogenic amines are determined with a high sensitivity by oxidation at an electrode with an OsO-RuCN film. Procedures for the voltammetric determination of DA, AD, or NAD at a composite film electrode are developed. The currents of the substrate oxidation are linear functions of the concentrations in the ranges from 5 × 10−7 to 1 × 10−3 M for DA and from 1 × 10−6 to 1 × 10−3 M for AD and NAD.

The chemical bonding, elastic behavior, phase stability, and hardness of OsB, OsB2, OsC, OsO2, OsN, and OsN2 have been systematically studied using first-principles calculations. The calculation suggests that the chemical bonding in these compounds is a mixture of covalent and ionic components. The structural stability of OsB, OsC, and OsN can be understood in terms of the band filling of the bonding states, and the results indicate that the hexagonal tungsten carbide structure is more stable. The hardness of these osmium compounds is calculated using both ab initio and semiempirical model calculations. Analysis of the ab initio hardness suggested that the large occupations and high strength of the covalent bonds are crucial for a superhard material, and there is no clear connection between bulk modulus and hardness in these osmium compounds.

RuOF4 as the highest valence oxide fluoride exist as a molecular compound (a = 606.0(1), b = 836.1(1), c = 626.3(1) pm, β = 91.637(3), Z = 4; P21/n) as well as fluorine bridged polymer (a = 547.7(2), b = 928.5(3), c = 1252.4(3) pm, Z = 8, P212121). A reproducible method for pure, deep blue OsOF4 is given. Pure OsOF4-I is isostructural to the fluorine bridged polymeric RuOF4 (a = 554.6(1), b = 955.4(2), c = 1278.4(2), Z = 8, P212121). OsOF4-II is also a fluorine bridged polymer (a = 537.8(2), b = 1274.8(4), c = 555.2(2), β = 117.716(6)°, Z = 4, P21/c). OsOCl4 again is a molecular species (a = 938.9(2), b = 561.3(1), c = 1192.0(2), β = 109.944(4)°, Z = 4, P21/c).

Osmium oxide/hexacyanoruthenate films have been prepared using repeated cyclic voltammetry, and their electrocatalytic properties have been investigated. The osmium oxide/hexacyanoruthenate films were deposited directly from mixed Os3+ and Ru ( CN ) 6 4 - ions in a pH 2 solution. Electrochemical quartz crystal microbalance (EQCM), cyclic voltammetry, and UV–visible spectroscopy were used to study the growth mechanism of the osmium oxide/hexacyanoruthenate films. The EQCM data indicated that the redox process was confined to the immobilized osmium oxide/hexacyanoruthenate film, which showed a single redox couple with a formal proton-dependent potential at 0.35 V. The electrocatalytic oxidation of dopamine, epinephrine, and norepinephrine and S 2 O 3 2 - and SO 5 2 - by the osmium oxide/hexacyanoruthenate films was studied. The electrocatalytic reactions of the osmium oxide/hexacyanoruthenate films were also investigated by the rotating ring-disk electrode method.

Interlocked supramolecular dendrimers were spontaneously self-assembled from molecular components, metallocycles, and dumbbells bearing benzyl ether repeating units. Here, the metallocycles were in situ self-assembled from L-shaped ligands with dendritic branches, 2,3-dimethyl-2-butene and osmium tetraoxide. The supramolecular dendrimers were stabilized by hydrogen-bonding interactions between the pyridine-2,6-dicarboxamide unit in the metallocycle and the adipamide unit in the dumbbell.

In the present work, the morphology and composition of osmium deposits formed in submonolayer amount on Pt(1 0 0) and Pt(1 1 1) single crystal surfaces either by spontaneous deposition or by electrolysis at 50 mV in different deposition times ( t dep ), were studied. The cyclic voltammetric curves for Pt(1 0 0)/Os and Pt(1 1 1)/Os were recorded in the potential range where the oxidation of deposited osmium species occurs, which suggests that the chemical composition of the deposits is a mixture of metallic Os and OsO 2 . The ratio of each species deposited depends directly on the deposition potential, as well as the surface structure characteristics. The composition of the modified platinum single crystal surfaces has also been estimated by X-ray photoelectron spectroscopy (XPS), whose results agree with those obtained by CV, about the amount of osmium oxide on Pt(1 1 1) to be higher than on Pt(1 0 0). This feature of the Pt(1 1 1)/Os becomes its surface more active for ethanol oxidation at lower potentials than that observed for Pt(1 0 0)/Os, although at high potentials the high presence of OsO 2 is prejudicial to the catalytic activity of the electrode. The Pt–Os surfaces were also explored by use of the scanning tunneling microscopy (STM) technique in order to image the features of osmium deposits on platinum, after a short and a long deposition time. It was found, by using spontaneous deposition procedure, that the dimensions of osmium deposits islands do not grow with the increase of degree of coverage of osmium on the surface, as well as they keep the monoatomic thickness.

Recently prepared layered double hydroxides (LDH)-supported OsO 4 , developed by the ion-exchange technique, was employed for catalytic asymmetric aminohydroxylation (AA) of olefins of varied nucleophilicity using Chloramine-T and (DHQ) 2 PHAL to afford chiral vicinal N-protected amino alcohols, important building blocks for many biologically active compounds and precursors for chiral ligands with moderate yields and ee's for the first time. Strong electron deficient olefins undergo AA reaction offering better yields than the less electron deficient and electron rich olefins due to the greater polarization of Os=NTs group in the former. The catalyst could be reused without any loss of enantioselectivity albeit a reduced activity.

A new catalyst derived from osmium has been prepared, fully characterized and tested in the dihydroxylation of alkenes. The catalyst was prepared by wet impregnation methodology of OsCl3·3H2O on a commercial micro-magnetite surface. The catalyst allowed the reaction with one of the lowest osmium loadings for a heterogeneous catalyst and was selective for the monodihydroxylation of 1,5-dienes. Moreover, the catalyst was easily removed from the reaction medium by the simple use of a magnet. The selectivity of catalyst is very high with conversions up to 99%. Preliminary kinetics studies showed a first-order reaction rate with respect to the catalyst. This work was supported by the Spanish Ministerio de Economía y Competitividad (CTQ2011-24151). J. M. P. thanks the M.E.C. for a fellowship through the FPI program.

Osmium tetroxide is a highly oxidizing, corrosive compound commonly found in electron microscopy laboratories. Although osmium tetroxide is known to cause rapid damage to organic tissue, its cutaneous effects have not been well studied. We report a case of traumatic inoculation from a broken vial of 4% osmium tetroxide. Electron microscopy and energy dispersive x-ray spectroscopy confirmed the presence of osmium in the tissue specimen. The lesion was treated by simple excision. (J Am Acad Dermatol 2001;45:949-52.)

A new, rapid, low-blank method for extraction of osmium from geological materials is described. As with existing techniques, this new Os accumulation procedure relies upon the oxidation of Os in the sample solution to OsO 4 and utilises the volatile nature of this oxide. In contrast to previous distillation methods, however, osmium oxide is caught in a cold trap, coated on its inner surface with sulfuric acid instead of bubbling an Os oxide bearing carrier gas through chilled HCl or HBr. Once the distillation is complete, the trapped Os is extracted into 500 μl of HBr concentration and undergoes a final cleaning step which can be accomplished by employing conventional micro-distillation techniques. The entire extraction procedure from the sample solution takes approximately 90 min and requires only 2 μl of H 2 SO 4 to trap the osmium, which is achieved with great efficiency. Thus, apart from the digestion medium, the extraction and recovery of Os in this technique employs a total of only ∼502 μl of reagents instead of approximately 5–10 ml in conventional procedures that ‘see’ the Os. As demonstrated here, the efficient extraction of Os and low reagent volumes required mean that it is possible to achieve yields of 80% and total procedural blanks of 100 fg routinely.

Phase structures of binary and ternary blends of polycarbonate (PC) with poly(styrene-co-acrylonitrile) (PSAN), and poly(methyl methacrylate-co-styrene) (PMMAS) were examined by transmission (TEM) and/or scanning transmission electron microscopy (STEM). Osmium or ruthenium tetroxides were applied to ultrathin sections and significant differences in the staining of phases were observed: PC was stained most intensely, while staining of the PSAN- and PMMAS-rich phases was affected by the concentration of the dissolved (partially miscible) PC. The blends within the phase inversion interval contained both PC continuous and PC dispersed phases, which were observed at different places on the sample cross-section. Three-phase structure, found in ultrathin sections of binary blends and confirmed on plasma-etched cut surfaces, is discussed from the point of view of likely artefacts; a possible interpretation considers non-uniform blending in the melt.

Polymer-supported oxidic osmium catalysts based on cross-linked poly(4-vinyl pyridine) were synthesized by various routes and characterized by a number of physical techniques (Raman, IR, XPS, 13 C and 15 N solid-state NMR spectroscopy). Model compounds of type Os 2 O 6 L 4 (L = pyridine, 4- iso -propyl pyridine, and 4- tert -butyl pyridine) were obtained under the conditions of the catalyst synthesis. The catalytic systems were successful in the dihydroxylation of alkenes.

Sidewall osmylation of individual metallic single-walled carbon nanotubes has been achieved by exposing the tubes to osmium tetroxide vapor under UV photoirradiation. The covalent attachment of the osmium oxide leads to an increase in the electrical resistance by up to several orders of magnitude. The cycloaddition product can be cleaved by UV light in vacuum or under an oxygen atmosphere, whereby the original resistance is restored. Single-walled carbon nanotubes (SWCNTs), with a diameter in the nanometer scale range and a length of several micrometers, represent attractive components for nanoscale electronic devices because of their unique electronic, mechanical, and chemical properties. 1 Depending on their chirality, SWCNTs are either metallic or semiconducting nanowires. 2 It is well documented that the electronic properties of SWCNTs are sensitive to the environment, 3,4 which constitutes the basis for using nanotubes in chemical sensors. 4-6 Recently, considerable effort has been directed toward chemical modification of the nanotube sidewall by attaching organic or inorganic functional groups. 6-16 Methods for sidewall functionalization include electrochemical attachment of phenyl groups, 7a,b decoration with selenium nanoparticles, 8 covalent attachment of nitrenes, 9 fluorination, 10a-c,11a,b ozonolysis, 12a,b and noncovalent attachment of

The fluorination of ruthenium dioxide, RuO 2 , and osmium di- and tetra-oxides, OsO 2 and OSO 4 , has been studied at ambient temperature using fluorinating agents of variable strength such as chlorine trifluoride ClF 3 , bromine pentafluoride BrF 5 or krypton difluoride KrF 2 . The results of this study and those previously obtained on the fluorination of ruthenium and osmium tetroxides (RuO 4 , OSO 4 ) are compared and discussed. The reaction of RuO 2 with KrF 2 in HF solution leads to the ruthenium(V) dioxygenyl salt, O 2 + RuF 6 − , and that of OsO 2 to osmium oxide pentafluoride, OsOF 5 . This oxide fluoride also results from the reaction of OsO 2 or OsO 4 with liquid ClF 3 . However, osmium trioxide difluoride, OsO 3 F 2 , and small quantities of osmium dioxide tetrafluoride, OsO 2 F 4 , are formed at intermediate stages of the fluorination of OsO 4 by ClF 3 . A slow reaction takes place between liquid BrF 5 and OsO 4 to yield OsO 3 F 2 as the sole osmium derivative. A large excess of KrF 2 or its derivative cation KrF + in HF solution leaves OsOF 5 unreacted. In contrast to the strength of the metal-oxygen bonds generally observed for the oxide fluorides of osmium in high oxidation states, the weakness of the corresponding Ru-O bonds is the rule. The differences between the fluorination pathways of the oxides of ruthenium and those of osmium are thus explained.

Osmium oxide hexafluoride OsOF 6 is prepared by fluorination of osmium tetraoxide using krypton difluoride in HF solution. This new Os (VIII) derivative is characterized by elemental analysis, X-ray powder data and vibrational spectroscopy. The fluorination of the ruthenium and osmium tetraoxides is compared and briefly discussed.

Na2OsO4 crystals were grown by a NaCl flux method under high pressure. It crystallizes in the Ca2IrO4-type structure without having additional elements or metal vacancies, which are usually accommodated. It appears that Na2OsO4 is a metal-stoichiometric Ca2IrO4-type compound never been synthesized to date. Na2OsO4 has the octahedral environment of Os6+O6 so that the electronic configuration is 5d2, suggesting the magnetic S=1 ground state. However, magnetization, electrical resistivity, and specific heat measurements indicated that the non-magnetic S=0 state is much likely for Na2OsO4 than the S=1 state. Band structure calculations and the structure analysis found that the disagreement is probably due to the statically uniaxial compression of the OsO6 octahedra, resulting in splitting of the t 2 g band.

The gaseous osmium oxide species OsO 4 , OsO 3 , OsO 2 , and OsO were generated by reaction of O 2 (g) with Os(c) in a heated alumina effusion cell, and thermochemical data were derived from equilibrium measurements made by mass spectrometry. Although OsO 4 and OsO 3 were observed as low as 1000 K, OsO 2 and OsO were detected only at temperatures above 1800 K

The Na-based osmium oxide pyrochlore was synthesized for the first time by an ion-exchange method using KOs{sub 2}O{sub 6} as a host. The composition was identified as Na{sub 1.4}Os{sub 2}O{sub 6}.H{sub 2}O by electron probe micro-analysis, thermogravimetric analysis, and structural analysis using synchrotron X-ray diffraction. Na{sub 1.4}Os{sub 2}O{sub 6}.H{sub 2}O crystallizes in a regular pyrochlore structure with some defects (space group: Fd-3m, a=10.16851(1) A). Electrical resistivity, heat capacity, and magnetization measurements clearly showed absence of superconductivity down to 2 K, being in large contrast to what was found for the beta-type pyrochlore superconductor AOs{sub 2}O{sub 6} (A=Cs, Rb, and K). The Sommerfeld coefficient is 22 mJ K{sup -2} mol{sup -1}, being the smallest among AOs{sub 2}O{sub 6}. A magnetic anomaly at {approx}57 K and associated magneto-resistance (+3.7% at 2 K in 70 kOe) were found. - Graphical abstract: Crystal structure of the Na-based Os oxide pyrochlore Na{sub 1.4}Os{sub 2}O{sub 6}.H{sub 2}O.

Osmium oxide hexafluoride OsOF 6 is prepared by fluorination of osmium tetraoxide using krypton difluoride in HF solution. This new Os (VIII) derivative is characterized by elemental analysis, X-ray powder data and vibrational spectroscopy. The fluorination of the ruthenium and osmium tetraoxides is compared and briefly discussed.

5d Solid-state oxides K0.84OsO3 (Os5.16+; 5d 2.84) and Bi2.93Os3O11 (Os4.40+; 5d 3.60) were synthesized under high-pressure and high-temperature conditions (6 GPa and 1500–1700 °C). Their crystal structures were determined by synchrotron x-ray diffraction and their 5d electronic properties and tunnel-like structure motifs were investigated. A KSbO3-type structure with a space group of Im-3 and Pn-3 was determined for K0.84OsO3 and Bi2.93Os3O11, respectively. The magnetic and electronic transport properties of the polycrystalline compounds were compared with those obtained theoretically. It was revealed that the 5d tunnel-like structures are paramagnetic with metallic charge conduction at temperatures above 2 K. This was similar to what was observed for structurally relevant 5d oxides, including Bi3Re3O11 (Re4.33+; 5d 2.66) and Ba2Ir3O9 (Ir4.66+; 5d 4.33). The absence of long-range magnetic order seems to be common among 5d KSbO3-like oxides, regardless of the number of 5d electrons (between 2.6 and 4.3 per 5d atom).

Single-walled carbon nanotubes have been reacted with osmium tetroxide (OsO(4)) in solution in the presence of O(2) and UV irradiation at 254 nm. We observe one main structural motif, namely thickly coated nanotube structures, densely covered with OsO(2), consisting of multiple bundles of derivatized tubes. In a few instances, bridging uncoated tubes, connecting these thickly coated structures, incorporate a number of smaller nanotube bundles, projecting out from the larger functionalized aggregates of tubes. It is believed that OsO(2) (a) initially forms on the nanotubes by the preferential covalent sidewall functionalization of metallic nanotubes and (b) subsequently self-aggregates. The formation of an intermediate charge-transfer complex is likely the basis for the observed selectivity and reactivity of metallic tubes. Extensive characterization of these osmylated adducts has been performed using a variety of electron microscopy and optical spectroscopy techniques.

A three-dimensional networked osmium nanomaterial (N-Os) was prepared by a thermal decomposition of Os3(CO)12 within mesopores of MCM-48. The novel N-Os species shows high catalytic activity and excellent reusability in the oxidation reactions of unsaturated compounds under mild conditions.

The periodic table provides a classification of the chemical properties of the elements. But for the heaviest elements, the transactinides, this role of the periodic table reaches its limits because increasingly strong relativistic effects on the valence electron shells can induce deviations from known trends in chemical properties. In the case of the first two transactinides, elements 104 and 105, relativistic effects do indeed influence their chemical properties, whereas elements 106 and 107 both behave as expected from their position within the periodic table. Here we report the chemical separation and characterization of only seven detected atoms of element 108 (hassium, Hs), which were generated as isotopes (269)Hs (refs 8, 9) and (270)Hs (ref. 10) in the fusion reaction between (26)Mg and (248)Cm. The hassium atoms are immediately oxidized to a highly volatile oxide, presumably HsO(4), for which we determine an enthalpy of adsorption on our detector surface that is comparable to the adsorption enthalpy determined under identical conditions for the osmium oxide OsO(4). These results provide evidence that the chemical properties of hassium and its lighter homologue osmium are similar, thus confirming that hassium exhibits properties as expected from its position in group 8 of the periodic table.

Exchanger-OsO 4 catalysts are prepared by an ion-exchange technique using layered double hydroxides and quaternary ammonium salts covalently bound to resin and silica as ion-exchangers. The ion-exchangers with different characteristics and opposite ion selectivities are specially chosen to produce the best heterogeneous catalyst that can operate using the various cooxidants in the asymmetric dihydroxylation reaction. LDH-OsO 4 catalysts composed of different compositions are evaluated for the asymmetric dihydroxylation of trans-stilbene. Resin-OsO 4 and SiO 2 -OsO 4 designed to overcome the problems associated with LDH-OsO 4 indeed show consistent activity and enantioselectivity in asymmetric dihydroxylation of olefins using K 3 Fe(CN) 6 and molecular oxygen as cooxidants. Compared to the Kobayashi heterogeneous systems, resin-OsO 4 is a very efficient catalyst for the dihydroxylation of a wide variety of aromatic, aliphatic, acyclic, cyclic, mono-, di-, and trisubstituted olefins to afford chiral vicinal diols with high yields and enantioselectivities irrespective of the cooxidant used. Resin-OsO 4 is recovered quantitatively by a simple filtration and reused for a number of cycles with consistent activity. The high binding ability of the heterogeneous osmium catalyst enables the use of an equimolar ratio of ligand to osmium to give excellent enantioselectives in asymmetric dihydroxylation in contrast to the homogeneous osmium system in which excess molar quantities of the expensive chiral ligand to osmium are invariably used. The complexation of the chiral ligand (DHQD) 2 PHAL, having very large dimension, a prerequisite to obtain higher ee, is possible only with the OsO 4 2- located on the surface of the supports.

A mild, organometallic alternative to ozonolysis utilizing oxone and OsO(4) is presented. This is a direct oxidation of olefins via the carbon-carbon cleavage of an osmate ester by the action of oxone. Twenty-four different olefins were converted to their corresponding ketones or carboxylic acids in high yields (80%). Free alcohols, acetate- and benzyl-protected alcohols, and 1,2-diols were stable under these conditions. This method should be applicable for traditional organic synthesis.

Magnetic and lattice properties of the pyrochlore NaxOs2O6?H2O were studied by a synchrotron X-ray diffraction method, measurements of magnetic susceptibility, electrical resistivity, and specific heat. The results indicated little change in the properties over the Na range 0.5 ? x ? 1.4. Any trace of superconductivity was undetected to 2 K.

A variant Golgi technique was developed that consisted of substituting osmium tetroxide with formaldehyde as the initial fixative in intracardiac perfusion, along with the addition of glacial acetic acid to the chromating fluid. This procedure avoids disposal of dangerous waste substances into the environment. Other advantages include 1) reduction of cost, danger to lab workers, and risk of disruption of the tissue slices during their handling by eliminating the osmium tetroxide, 2) clear tissue background, 3) greater quantity of impregnated neurons than in the classical procedure, with distinct morphological details easily identified even in gross sections and 4) reduction in processing time.

Inelastic neutron scattering and neutron powder diffraction experiments were carried out to investigate a localized mode, proposed from various bulk measurements, in the beta-pyrochlore AOs2O6 (A=K, Rb, Cs). The localized mode was identified in all the three compounds as well as another beta-pyrochlore CsW2O6. The anharmonicity of the mode is weak in RbOs2O6 and CsOs2O6 but substantial in KOs2O6., Comment: 12 pages, 6 figures; typos and graph corrected

Superconductivity in the potassium osmium oxide KOs2O6 crystallizing in the beta-pyrochlore structure is studied by means of electrical resistivity, magnetic susceptibility and specific heat. It is the second superconductor in the family of pyrochlore oxides, following the alfa-type pyrochlore oxide Cd2Re2O7 which is believed to be a conventional s-wave superconductor. The superconducting transition temperature Tc of KOs2O6 is 9.6 K, almost one order higher than the Tc = 1.0 K of Cd2Re2O7. Moreover, the superconductivity of KOs2O6 is remarkably robust under high magnetic fields, with a large upper critical magnetic field Hc2 of about 38 T, which seems to exceed Pauli's limit expected for conventional superconductivity. This is also in contrast to the case of Cd2Re2O7, in which the Hc2 is 0.29 T, much smaller than the corresponding Pauli's limit. These distinct contrasts strongly suggest that the mechanism of superconductivity is essentially different between the two pyrochlore oxides.

Previous investigations on fluorides and oxide fluorides of ruthenium [1,2] had indicated that some of the results could be extended and / or better explained through similar studies on osmium derivatives. This paper describes the first results obtained in that connection. Among the most noticeable results it was found that osmium tetraoxide, OsO 4 , could be fluorinated by krypton difluoride in HF solution into osmium oxide hexafluoride, OsOF 6 . This new oxide fluoride of osmium in the formal oxidation state +8 was characterized by elemental analysis, X-ray powder data and vibrational spectroscopy. Results concerning the synthesis and characterization of difluorochlorine (III) hexafluoro-osmate (V), [CIF 2 ]+[OsF 6 ] − are also presented.

The emission spectrum of OsO has been photographed in the region 405–875 nm where many new bands have been observed. In favorable cases the 190 OsO 192 OsO isotopic splittings have been resolved and aid in vibrational assignments. Three visible bands in the region 433–470 nm have been assigned as (1,0), (0,0), and (0,1) of a ΔΩ = 0 electronic transition. The (0,0) and (0,1) bands have been rotationally analyzed, yielding principal constants (cm−1) for the visible system of ν0 = 22 273.3, B′0 = 0.3657, D′0 = 2.8 × 10−7, B″e = 0.4023, D″e = 3.2 × 10−7, Δ G″( 1 2 ) = 780.7 , and Δ G″( 1 2 ) = 884.9 . A band at 825.4 nm has been found to be a ΔΩ = +1 (0,0) band with the same lower state as in the analyzed visible bands. Constants for the upper state of the ir system are ν0 = 12 109.7, B′0 = 0.3845, and D′0 = 3.1 × 10−7 cm−1.

Selective contrast staining of glycogen in untreated ultrathin sections of aldehyde-fixed tissues, double-fixed with 1% osmium tetroxide containing 0.05m K3Fe(CN)6 as reported previously (De Bruijn, 1973), may also be obtained by the addition of either K4Fe(CN)6, K3Co(CN)6, K2Ru(CN)6, or K4Os(CN)6. On the other hand, addition of K3Cr(CN)6, K2Ni(CN)4, K3Mn(CN)6, K3Rh(CN)6, K2Pd(CN)4, K2Pt(CN)4, or K3Ir(CN)6 produces no effect. Hexavalent osmium oxide compounds, such as K2OsO4 and OsO3.2 pyridine, react selectively with a native (or acquired) ligand in the aldehyde-fixed glycogen, but do not render it more electron dense than its immediate surroundings. The presence of these osmium oxides is detected and they are rendered more electron dense by an accumulation reaction by the application on ultrathin sections of phosphotungstic acid (PTA) or a mixture of K2OsO4 and K4Fe(CN)6. As selective contrast staining of glycogen is also obtained by double fixation of the aldehyde-fixed tissue with 0.05m K2OsO4 solutions containing 0.05m K4Fe(CN)6 or 0.05m K4Os(CN)6, it is postulated that in such tissue, both the selective reaction of K2OsO4 with the ligand in the aldehyde-fixed glycogen, and the accumulation of heavy metal at the sites occupied by the K2OsO4, occur simultaneously. A proposal for the constitution of this heavy metal osmium/cyanide complex is formulated and arguments are presented that both compounds are formed in the selective contrast stained glycogen areas of such treated tissues. The relative contribution of the components to the final contrast and its complex character is demonstrated by staining ultrathin glutaraldehyde sections intermittently with 0.05m solutions of K2OsO4 and K4Fe(CN)6; it is shown that after at least three intermittent reactions with both K2OsO4 and K4Fe(CN)6, the glycogen areas in such sections became contrast stained.

The fine structure of Chinon fibers treated with some proteases was examined. Under optical microscope, the cross sections of Chinon fiber stained with C. I. Acid Red 249 revealed that Pronase P (Pro) and Proteoliquifase (Plf) both eliminated the protein component of the fiber progressively from its surface region to the center, while the distribution of protein was apparently uniform in the intact fibers. On the other hand, Papain C-400 (Pap) seemed to digest the protein uniformly under the same conditions. Under transmission electron microscope, the cross sections stained with osmium oxide revealed that the protei component distributed uniformly in Chinon fiber as fine units of less than 200 A in diameter. Furthermore, it was observed that Pro and Plf decreased not only the diameter but also the density of the protein units according to the progress of the proteolysis, while Pap seemed to decrease only the density but not the diameter of the components. Thus, introduction of certain micro-void spaces was expected at the positions corresponding to those stainable by osmium oxide before but unstainable after the proteolysis. However, direct observation by a scanning electron microscope was unable to detect the micro-void spaces probably because of their dimension out of the resolution.

The infrared spectra of ReOCl4 and OsOCl4 have been measured in the gas phase, in the condensed phase, and in a variety of solvents. In the gas phase spectra the absorption band envelopes corresponding to the metal-oxygen stretching vibrations have been observed and the data are discussed in terms of possible square pyramidal or trigonal bipyramidal structures for the molecules. Evidence is presented showing that acetone and diethyl ether molecules will readily coordinate to these oxide tetrachlorides when dissolved in inert solvents. The effect of traces of water on the same solutions is also described and discussed. Both ReOCl4 and OsOCl4 react with the solvent if dissolved in acetone or diethyl ether and the possibility of the formation of the unknown oxide trichlorides is discussed.

The emerald green solid, OsOF5, m. p. 59·2, b. p. 100·6°, is the major product of the fluorination of osmium dioxide. Vapour pressure–temperature relationships for the compound are: 32–59°(solid), log Pmm=–2266//T+ 9·064; 59–105°(liquid), log Pmm=–1911//T+ 7·994. The solid is dimorphic being orthorhombic below the transition point of 32·5° and body centred cubic, a= 6·14 A, above it. It is paramagnetic and the susceptibility obeys the Curie-Weiss law approximately, with θ=+6°, the temperature independent magnetic moment being, µ= 1·47 B.M. The infrared spectrum of OsOF5(gas) is similar to that of ReOF5(gas) and is consistent with C4v molecular symmetry.

Osmium oxide tetrafluoride OsOF4 has been prepared in good yield by the reduction of OsOF5 on a hot tungsten filament and has been characterized by chemical analysis, molecular beam mass spectroscopy, and X-ray crystallography.

Crystals of osmium oxide pentafluoride, OsOF5, the first heptavalent osmium compound prepared, are orthorhombic below 32·5°, with four molecules in a unit cell of dimensions a= 9·540, b= 8·669, c= 5·019 A, space group Pnma. The structure was determined from the isostructural relationship with the actinide hexafluorides, and refined by three-dimensional Fourier and difference syntheses.The OsOF5 units of the molecular lattice are distorted from octahedral ligancy. The nature of the distortion is consistent with the greater effective size of the oxygen ligand compared with the fluorine ligands and is indicative of an ordered structure. The chemically significant interatomic distances are: Os–O 1·74 ± 0·03, the trans-Os–F 1·72 ± 0·03, two equatorial Os–F 1·76 ± 0·03, two equatorial Os–F 1·80 ± 0·03 A.