20816-12-0

Basic information

• Product Name: Osmium tetroxide
• Synonyms: OSMIUM TETRAOXIDE;OSMIUM TETROXIDE;OSMIUM TETROXIDE SOLUTION;OSMIUM(VIII) OXIDE;OSMIUM(VIII) OXIDE (TETROXIDE);OSMIUM (VIII) TETRAOXIDE;OSMIUM(VIII)-TETROXIDE;OSMIUM(+8)OXIDE
• CAS NO: 20816-12-0
• Molecular Formula: O₄Os
• Molecular Weight: 254.23
• EINECS: 244-058-7
• Product Categories: Inorganics;Os (Osmium) Compounds;Classes of Metal Compounds;Oxidation;Synthetic Organic Chemistry;Transition Metal Compounds;OsmiumEssential Chemicals;Reagent Grade;Routine Reagents;Synthetic Reagents;metal oxide
• Mol File: 20816-12-0.mol
• Article Data: 13

Chemical Properties

• Melting Point: 40°C
• Boiling Point: 130 °C
• Flash Point: -40 °C
• Appearance: White to yellow,or lemon yellow/Solution
• Density: 1.04
• Vapor Density: 8.8 (vs air)
• Vapor Pressure: 7 mmHg at 20 °C
• Storage Temp.: Refrigerator
• Solubility: Soluble in alcohol, ether, chloroform, benzene, ammonium hydroxi
• Water Solubility: Soluble in chloroform, alcohol and ethers.Soluble in water, organic solvents, benzene, alcohol, ether, ammonium hydroxide, phosp
• Sensitive: Air Sensitive
• Stability: Stable. Incompatible with strong acids, hydrogen chloride, organic materials, finely powdered metals.
• Merck: 14,6893
• CAS DataBase Reference: Osmium tetroxide(CAS DataBase Reference)
• NIST Chemistry Reference: Osmium tetroxide(20816-12-0)
• EPA Substance Registry System: Osmium tetroxide(20816-12-0)

Safety Data

• Hazard Codes: O,T,C,T+,F,Xi,Xn
• Statements: 8-23/24/25-40-34-26/27/28-42/43-11-67-66-36/37/38-19-36/38-36/37
• Safety Statements: 17-26-27-36/37/39-45-7/9-36/37-16-28-23
• RIDADR: UN 3175 4.1/PG 2
• WGK Germany: 3
• RTECS: RN1140000
• TSCA: Yes
• HazardClass: 6.1
• PackingGroup: I
• Hazardous Substances Data: 20816-12-0(Hazardous Substances Data)

Usage

Description

Osmium tetroxide (OsO4) is a colorless or pale yellow crystalline solid with a pungent chlorine-like odor. It is a strong oxidizing agent and is soluble in most organic solvents and moderately soluble in water. Osmium tetroxide is a volatile oxide of a heavy metal and is one of the few that can be easily prepared. It has a number of specific applications in organic chemistry and biochemistry.

Uses

Used in Histo病理学 Laboratories:
Osmium tetroxide is used as a staining agent for adipose tissue and as a stabilizing agent in scanning electron microscopy.
Used in Chemical Industry:
Osmium tetroxide is used as a catalyst in organic synthesis, particularly as the oxidizing agent in olefin-to-glycol conversion.
Used in Forensic Medicine:
In the past, osmium tetroxide in the form of an aqueous solution was used to examine fingerprints.
Used in Medicine:
Osmium tetroxide is used to treat rheumatoid arthritis.
Used as an Oxidizing Agent:
Osmium tetroxide is a strong oxidizing agent used for converting olefins to glycols and catalyzes chlorate, peroxide, periodate, and other oxidations.
Used in Biochemistry Field:
Osmium tetroxide is used as a fixing and staining agent for cell and tissue studies, particularly for visible and electron microscopy of biological materials. It is used for preserving sub-cellular ultrastructure and fixing and staining membranes.
Used in Synthesis of 3-[1-(2,4-Dichlorophenyl)-2-(1H-imidazol-1-yl)ethoxy]-1,2-propanediol (D436535):
Osmium tetroxide is used as a reagent in the dihydroxylation process in the synthesis of D436535, which is involved in biological studies as microsomal cytochrome P 450 isoenzymes from Penicillium italicum interaction with sterol demethylation inhibitor fungicides.
Used in Passivation of Iron Electrodes:
Like some other heavy metal tetra-oxo species, osmium tetroxide has the property of passifying iron electrodes in electrolytes.

History and preparation

The compound was discovered in 1803 by Smithson Tennant (1761-1815), and in the same year he isolated metallic osmium from it[2]. Fusion with alkali of the black residue remaining after treatment of native platinum with aqua regia followed by extraction and acidification of the melt gave. Industrially, OsO4, is made from crude platinum concentrates by oxidative acid distillation and is then separated from ruthenium tetroxide. In the laboratory it is best made by direct oxidation of osmium metal[3] or by the acid distillation with chlorate of almost any osmium compound

Properties

Osmium tetroxide is a non-combustible, colorless to pale yellow solid that has a disagreeable chlorine-like odor[4]. It slowly develops when powdered osmium metal is exposed to air. OsO4 is fairly soluble in water and in several organic solvents, but reacts as an oxidant with many of them. The substance is used in organic syntheses, mainly to oxidize unsaturated carbon-carbon bonds to dihydroxy compounds (glycols). Its most common usage is as a staining agent and a “fixant” in transmission electron microscopy. This chemical sublimes at room temperature, having a remarkable vapor pressure of about 7 mmHg at 20oC (more typical for a liquid compound than for a solid), as compared to 17 mmHg for water, 2 mmHg for the nerve agent sarin, or 0.07 mmHg for the blistering agent sulfur mustard under the same conditions. It is highly poisonous, even at very low concentrations, and must be handled according to the appropriate precautions. Hours may pass between exposure and the appearance of noticeable symptoms. In almost all of its chemical reactions, a number of which are summarized in the diagram, OsO4, is reduced to compounds containing lower oxidation states. With ammonia, however, the tetrahedral osmiamate ion[OsO3, N]is formed, which is isoelectronic with OsO4.

Toxicity and health effect

OsO4 has an odor threshold of 0.0019 parts/million. Its lethal concentration time (LCt50) is considered to be 1316 mg/min/m3, similar to that for sulfur mustard[11]. Humans may tolerate a maximal concentration of 0.1 ppm in air for 1.5 hours or 0.0001 ppm for 6 hours without harmful effects[12]. McLaughlin and co-authors[13] reported that workers exposed to 0.01–0.53 ppm (0.1–0.6 mg/m3) suffered from lacrimation, conjunctivitis, vision disturbances, headaches and cough. OsO4 can be compared to chemical warfare agents in terms of toxicity. Exposure to even low doses can be lethal. In addition, both OsO4 and chemical warfare agents share similar physiological effects. The first appearance of a physiological effect, also known as the threshold effect, is observed at a lower concentration for osmium tetroxide vapor than for chemical warfare agents such as phosgene, sulfur mustard or even the nerve agent sarin. The LCt50 of OsO4 is comparable to that of sulfur mustard, but since sulfur mustard has a much lower vapor pressure OsO4 can pose a greater inhalational threat. Under the same environmental conditions there will be much more OsO4 vapor in a closed space than sulfur mustard vapor[1]. Osmium tetroxide is a rapid, indiscriminative oxidizer that does not distinguish between organic tissue and inorganic materials. An inhalational toxicity study with rabbits proved futile, because of the rapid reduction of OsO4 by the skin, hair, mucous membranes, etc., as well as by the chamber walls[14]. Inhalation, ingestion, contact with skin and with mucous membranes may all result in severe consequences. Due to its high vapor pressure, most exposures are to vapor. These can cause severe chemical burns to the eyes, skin and respiratory tract[15]. Very short-term contact with the vapor may cause lacrimation, accompanied by cough, headaches and dizziness. OsO4 may cause irreversible blindness by turning the cornea black. Symptoms may not be noticeable until several hours after the exposure, which may be an appealing feature for terrorists. Affected people may not realize immediately the extent of its toxic effects. Another severe delayed effect following inhalational exposure is acute lung injury, which may be followed by non-cardiogenic pulmonary edema[1]. Direct contact with osmium tetroxide solution will turn the skin black (severe chemical burns due to strong oxidizing properties). Painful burns or contact dermatitis may result, depending on the concentration. OsO4 is not considered a carcinogen[1]. Death is mainly the result of complications due to the exposure.

Medical care

Neutralization of the chemical on surfaces can be conveniently achieved by covering it with unsaturated oil (vegetable oil)[1]. Osmium tetroxide does not have a medical antidote; therefore the treatment is supportive and symptomatic, depending on the route of exposure. Initial treatment should focus on preventing further exposure. Victims should be removed from the contaminated area, undressed, and decontaminated by running water as soon as possible.

Analytic methods

Spectrum method In general, the 1960-90s saw a big growth in spectral and optical methods for determining osmium. One of the first methods was X-ray fluorescence, with a lot of benefits such as accuracy, non-destructiveness, and the ability to detect osmium without chemical extraction from biological samples. Also, this method is independent of the chemical state of osmium atoms. It was observed that the reaction of OsO4 with thiourea in acid medium gave a red combination of[Os(thio)6]Cl3[16]. The results were not affected by systematic errors. The convenient, sensitive, reproducible, and accurate method for the spectrophotometric determination of osmium has been developed. Electrochemical methods A rapid potentiometric method was proposed by Zaky et al.[17]. The method is based on the addition of arsenite to Os(VIII) to reduce it to the metallic state. The excess of arsenite was oxidized by iodine dissolved in acetic acid. The liberated iodide was then potentiometrically titrated against mercury (II) using silver amalgam as the indicator electrode. Some binary and ternary mixtures were completely analyzed. Amin and Saleh described a simple, rapid, and accurate potentiometric method for the determination of Os (VIII) in the concentration range 0.4-4.0 mg?ml-1[18]. Hydrazine hydrochloride was added to Os (VIII) to reduce it to Os (IV). The excess of hydrazine hydrochloride was oxidized by iodine dissolved in acetic acid.

References

Baker M, Kosal ME. Osmium Tetroxide – a New Chemical Terrorism Weapon? http://CNS miis edu/pubs/week/040413 htm 2004 D. McDonald, Platinum Metals Rev., 1961, 5, 146; Smithson Tennant, Phil. Trans., 1804, 94, 411 G. Brauer, Handbook of Preparative Chemistry, Academic Press, New York, 1965, p. 1603 Material Safety Data Sheet (MSDS). Osmium tetroxide. http://www proscitech com au/catalogue/msds/c010 pdf 2007. L. F. Fieser and M. Fieser, Reagents for Organic Synthesis, Wiley, New York, 1967, PP 475,759 R. Criegee, B. Marchand and H. Wannowius,Ann., 1942, 550, 99 G. M. Badger, Qzturt. Rev., 1951,5,160 R. J. Collin, W. P. Griffith, F. Phillips and A. C. Skapski, Biochim. Biophys. Acra, 1973, 320, 745; J. Chem. Soc., Dalton Trans., 1974, I094 R. Pappo, D. S. Allen, R. U. Lemieux and W. S. Johnson, J. Org. Chem., 1956,z1,478 G. H. Cartledge, Corrosion, 1967,18,316t CBWInfo.com. Improvised Chemical Agent: Osmium Tetroxide. http://cbwinfo com/Chemical/HistandMisc/oso4 shtml 2004. Grant WM. Toxicology of the Eye. 2nd edn. Springfield, IL: Charles C. Thomas, 1974:769. McLaughlin AIG, Milton R, Perry KMA. Toxic manifestations of osmium tetroxide. Br J Ind Med 1946;3:183–6. Osmium Tetroxide. MSDS Division of Occupational Health and Safety. http://dohs ors od nih gov/pdf/Osmium%20Tetroxide%20REVISED pdf 2007. National Academy of Sciences. Prudent Practices in the Laboratory: Handling and Disposal of Chemicals.Washington, DC: National Academies Press, 1995:364. BRATULESCU G., GANESCU I., GANESCU A. Thiocyanatochrome complexes in analytical chemistry. Determination of osmium(III). J. Serb. Chem. Soc. 70, (8-9), 1113, 2005. ZAKY M., KILLA H.M., ISSA Y.M. Some observations on the application of arsenite reduction to the potentiometric determination of osmium(VIII) and to the analysis of mixtures. Microchem. J. 44, (1), 54, 1991. AMIN A.S., SALEH H.M. Utilization of hydrazine hydrochloride in the potentiometric determination of osmium(VIII): Analysis of binary and ternary mixtures. Sci. Pharm. 69, (2), 367, 2001.

Production Methods

Osmium tetroxide is obtained by heating, at 300–400°C, finely divided osmium metal in the stream of air or oxygen (546). Commercially, it is received during osmium smelting and platinum annealing. Osmium tetroxide may also be produced by oxidizing osmium with aqua regia or nitric acid. It is often formed at room temperature from osmium metal powder.

Preparation

Osmium tetroxide is obtained as an intermediate during recovery of osmium metal from osmiridium or other noble metal minerals (See Osmium). In general, oxidation of an aqueous solution of an osmium salt or complex, such as sodium osmate with nitric acid, yields the volatile tetroxide which may be distilled out from the solution. In the laboratory, the compound can be prepared by oxidation of the osmium tetrachloride, OsCl4, or other halide solutions with sodium hypochlorite followed by distillation. Osmium tetroxide may also be produced by heating finely divided osmium metal in a stream of oxygen or air at 300 to 400°C.

Air & Water Reactions

Soluble in water.

Reactivity Profile

Osmium tetraoxide is incompatible with hydrochloric acid andeasily oxidized organic materials. Contact with other materials may cause fire. . Reacted explosively with1-methylimidazole [J. Chem. Soc., Dalton Trans., 1979, 1084].

Hazard

Osmium tetroxide is poisonous by all routes of exposure. The vapor is an eye irritant and can produce tears and damage. The vapor also can cause upper respiratory tract irritation. LD50 oral (mouse): 162 mg/kg LCLO inhalation (mouse): 40 ppm (104 mg/m 3)/4 hr.

Health Hazard

TOXIC; inhalation, ingestion or skin contact with material may cause severe injury or death. Contact with molten substance may cause severe burns to skin and eyes. Avoid any skin contact. Effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.

Health Hazard

The acute toxicity of osmium tetroxide is high, and it is a severe irritant of the eyes and respiratory tract. Exposure to osmium tetroxide vapor can damage the cornea of the eye. Irritation is generally the initial symptom of exposure to low concentrations of osmium tetroxide vapor, and lacrimation, a gritty feeling in the eyes, and the appearance of rings around lights may also be noted. In most cases, recovery occurs in a few days. Concentrations of vapor that do not cause immediate irritation can have an insidious cumulative effect; symptoms may not be noted until several hours after exposure. Contact of the eyes with concentrated solutions of this substance can cause severe damage and possible blindness. Inhalation can cause headache, coughing, dizziness, lung damage, and difficult breathing and may be fatal. Contact of the vapor with skin can cause dermatitis, and direct contact with the solid can lead to severe irritation and burns. Exposure to osmium tetroxide via inhalation, skin contact, or ingestion can lead to systemic toxic effects involving liver and kidney damage. Osmium tetroxide is regarded as a substance with poor warning properties. Chronic exposure to osmium tetroxide can result in an accumulation of osmium compounds in the liver and kidney and damage to these organs. Osmium tetroxide has been reported to cause reproductive toxicity in animals; this substance has not been shown to be carcinogenic or to show reproductive or developmental toxicity in humans.

Fire Hazard

Noncombustible

Fire Hazard

Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.). Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated.

Flammability and Explosibility

Noncombustible

Safety Profile

Poison by ingestion, inhalation, and intraperitoneal routes. Human systemic effects by inhalation: lachrymation and other eye effects and structural or functional changes in trachea or bronch. Experimental reproductive effects. Mutation data reported. Explodes on contact with 1 -methylimidazole. Catalytic decomposition of hydrogen peroxide can be hazardous. See also OSMIUM

Potential Exposure

Osmium may be alloyed with platinum metals, iron, cobalt, and nickel; and it forms compounds withtin and zinc. The alloy with iridium is used in the manufacture of fountain pen points, engraving tool; record player needles; electrical contacts; compass needles; fine machine bearings; and parts for watch and lock mechanisms. The metal is a catalyst in the synthesis of ammonia; and in the dehydrogenation of organic compounds. It is also used as a stain for histological examination of tissues. Osmium tetroxide is used as an oxidizing agent, catalyst, and as a fixative for tissues in electron microscopy. Other osmium compounds find use in photography. Osmium no longer is used in incandescent lights or in fingerprinting.

storage

In particular, all work with osmium tetroxide should be conducted in a fume hood to prevent exposure by inhalation, and splash goggles and impermeable gloves should be worn at all times to prevent eye and skin contact. Osmium tetroxide as solid or solutions should be stored in tightly sealed containers, and these should be placed in secondary containers.

Purification Methods

It is VERY TOXIC and should be manipulated in a very efficient fume cupboard. It attacks the eyes severely (use also face protection) and is a good oxidising agent. It is volatile and has a high vapour pressure (11mm) at room temperature. It sublimes and volatilises well below its boiling point. It is soluble in *C6H6, H2O (7.24% at 25o), CCl4 (375% at 25o), EtOH and Et2O. It is estimated by dissolving a sample in a glass-stoppered flask containing 25mL of a solution of KI (previously saturated with CO2) and acidified with 0.35M HCl. After gentle shaking in the dark for 30minutes, the solution is diluted to 200mL with distilled H2O saturated with CO2 and titrated with standard thiosulfate using starch as indicator. This method is not as good as the gravimetric method. Hydrazine hydrochloride (0.1 to 0.3g) is dissolved in 3M HCl (10mL) in a glass-stoppered bottle. After warming to 55-65o, a weighed sample of OsO4 solution is introduced, and the mixture is digested on a water bath for 1hour. The mixture is transferred to a weighed glazed crucible and evaporated to dryness on a hot plate. A stream of H2 is started through the crucible, and the crucible is heated over a burner for 20-30minutes. The stream of H2 is continued until the crucible in cooled to room temperature, and then the H2 is displaced by CO2 in order to avoid rapid combustion of H2. Finally the crucible is weighed. [Grube in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol II pp 1603 1965, Anderson & Yost J Am Chem Soc 60 1822 1938.] § Available commercially on a polymer support.

Incompatibilities

Osmium tetroxide is a strong oxidizer. Reacts with combustibles and reducing materials. Reacts with hydrochloric acid to form toxic chlorine gas. Forms unstable compounds with alkalis.

Waste Disposal

Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform with EPA regulations governing storage, transportation, treatment, and waste disposal.

InChI:InChI=1/4O.Os/rO4Os/c1-5(2,3)4

Upstream product

• 7722-84-1 dihydrogen peroxide 
• 13444-93-4 osmium(III) chloride 
• 124-38-9 carbon dioxide 
• 7697-37-2 nitric acid 
• 10026-01-4 osmium tetrachloride 

Downstream Products

• 50381-48-1 trioxo(N-tert-butylimido)osmium(VIII) 
• 63174-13-0 bis(tert-butylimino)dioxoosmium 
• 63174-16-3 tris(N-tert-butylimido)oxoosmium(VIII) 
• 18533-24-9 mer-trichlorotris(di-n-butylphenylphosphine)osmium(III) 
• 22671-02-9 mer-Os(P(n-Bu)2Ph)3Br₃ 
• 12036-02-1 osmium dioxide 
• 84-65-1 9,10-phenanthrenequinone 
• 22671-03-0 mer-{OsCl₃(PEtPh₂)3} 
• 23677-84-1 mer-{OsCl3(PEt2Ph)3} 

Relevant articles and documents

K2NaOsO5.5 and K3NaOs2O 9: The first osmium perovskites containing alkali cations at the A site

K2NaOsO5.5 and K3NaOs2O 9 were obtained from solid-state reactions of potassium superoxide, sodium peroxide and osmium metal at elevated oxygen pressures. K 2NaOsO5.5 crystallizes as an oxygen-deficient cubic double perovskite in space group Fm3m with a=8.4184(5) A and contains isolated OsO6 octahedra. K3NaOs2O9 crystallizes hexagonally in P63/mmc with a=5.9998(4) A and c=14.3053(14) A. K3NaOs2O9 consists of face sharing Os2O9 pairs of octahedra. According to magnetic measurements K2NaOsO5.5 is diamagnetic, whereas K3NaOs2O9 displays strong antiferromagnetic coupling (TN=140 K), indicating enhanced magnetic interactions within the octahedral pair.

Competition of methyltrioxorhenium (MTO) with osmium tetroxide (OsO 4) for pyridines binding: Ligand binding assay

Competition of methyltrioxorhenium (MTO) with osmium tetroxide (OsO 4) toward L = pyridine and its derivatives, based on the equilibrium constant for the reaction OsO4·L + MTO = MTO·L + OsO4, has been measured. A successful correlation of log K eq with the Hammett σ constants of the substituents on the ligands was realized. A negative reaction constant, obtained for the reactions, shows that a more positive charge expands on the pyridine nitrogen in the complex MTO·L as compared with the complex OsO4·L. So, the rhenium center acts as a better electron acceptor than osmium center. The thermodynamic parameters have been obtained and an excellent linear relationship was observed between the enthalpy and entropy of the reactions.

A spectroscopic (stopped-flow UV–Vis and1H NMR Evans method) and DFT thermodynamic study of the comproportionation reaction of [OsVIIIO4(OH)n]n?(n = 1, 2) and [OsVIO2(OH)4]2?

From a mole ratio1H NMR Evans method experiment it is found that, in a 2.0 M NaOH aqueous matrix, diamagnetic [OsVIIIO4(OH)n]n?(n = 1, 2) (of d0electron configuration) and trans-[OsVIO2(OH)4]2?species (d2) react in a 1:1 mol ratio to form two paramagnetic OsVIIoxido/hydroxido product species (d1). This result is further validated as the chemical reaction model that best fitted stopped-flow UV–Vis spectroscopy kinetic data is given by OsVIII+OsVI?kCOMkCOM2OsVII. From non-linear least squares fits of stopped-flow UV–Vis spectroscopy kinetic traces the comproportionation reaction rate constants, activation energies (forward: ΔH?(obs), ΔS?(obs)and ΔG?(obs)are 10.3 ± 0.5 kcal mol?1, ?2.6 ± 1.6 cal mol?1K?1and 11.1 ± 0.9 kcal mol?1, respectively; and reverse are ?6.7 ± 1.0 kcal mol?1, ?63.6 ± 3.4 cal mol?1K?1and 12.2 ± 2.0 kcal mol?1respectively) and standard reaction energies (ΔH°rxn(obs), ΔS°rxn(obs)and ΔG°rxn(obs)are 17.1 ± 1.2 kcal mol?1, 61.0 ± 4.3 cal mol?1K?1and ?1.1 ± 2.5 kcal mol?1, respectively) at 298.15 K were determined. Stopped-flow kinetic isotope experiments provide evidence that these redox reactions coincide with the transfer of a proton. A systematic DFT speciation study of OsVIand OsVIIoxido/hydroxido complexes in a simulated aqueous phase (COSMO) yield that the thermodynamically most stable OsVIspecies is the singlet spin state trans-[OsVIO2(OH)4]2?complex and the thermodynamically most stable paramagnetic OsVIIproduct species are a combination of trans-[OsVIIO3(OH)2]?and mer-[OsVIIO3(OH)3]2?species. Using the DFT results, the OsVI& OsVIIIcomproportionation reaction is now proposed to be [OsVIIIO4(OH)2]2?reacts with trans-[OsVIO2(OH)4]2?to yield two trans-[OsVIIO3(OH)2]?species and two hydroxide anions. The DFT-calculated standard reaction energies for this reaction at 298.15 K (e.g. with the PBE functional, ΔH°rxn, ΔS°rxnand ΔG°rxnare 21.13 kcal mol?1, 71.06 cal mol?1K?1and ?0.06 kcal mol?1, respectively) compare exceptionally well with the obtained experimental data.

Ag13OsO6: A silver oxide with interconnected icosahedral Ag134+ clusters and dispersed [OsO 6]4- octahedra

The tendency for silver-rich compounds to form higher agglomerates of silver atoms or ions is well known. The synthesis of Ag13OsO 6 represents the first compound in the Ag/Os/O system. Besides [OsO6]4- octahedra, the compound contains icosahedrally shaped Ag134+ clusters (see picture), which are observed for the first time in solid silver oxides.