Osmium tetroxide is the chemical compound with the formula OsO₄. The compound is noteworthy for its many uses, despite the rarity of osmium. It has a number of interesting properties, one being that the solid is volatile. Image File history File links Size of this preview: 601 × 600 pixelsFull resolution (1094 × 1092 pixel, file size: 125 KB, MIME type: image/png) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Osmium(VIII) oxide ... IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... This article does not cite its references or sources. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... In physics, density is mass m per unit volume V. For the common case of a homogeneous substance, it is expressed as: where, in SI units: ρ (rho) is the density of the substance, measured in kg·m-3 m is the mass of the substance, measured in kg V is... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... Solubility refers to the ability for a given substance, the solute, to dissolve in a solvent. ... This article describes water from a scientific and technical perspective. ... The melting point of a crystalline solid is the temperature at which it changes state from solid to liquid. ... The boiling point of a substance is the temperature at which it can change its state from a liquid to a gas throughout the bulk of the liquid at a given pressure. ... The acid dissociation constant (Ka), also known as the acidity constant or the acid-ionization constant, is a specific equilibrium constant for the reaction of an acid with its conjugate base in aqueous solution [1]. // When an acid dissolves in water, it partly dissociates forming hydronium ions and its conjugate... An example MSDS in a US format provides guidance for handling a hazardous substance and information on its composition and properties. ... Council Directive 67/548/EEC of 27 June 1967 on the approximation of laws, regulations and administrative provisions relating to the classification, packaging and labelling of dangerous substances (as amended) is the main source of European Union law concerning chemical safety. ... R-phrases are defined in Annex III of European Union Directive 67/548/EEC: Nature of special risks attributed to dangerous substances and preparations. ... S-phrases are defined in Annex IV of European Union Directive 67/548/EEC: Safety advice concerning dangerous substances and preparations. ... The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. ... The relative dielectric constant of a material under given conditions is a measure of the extent to which it concentrates electrostatic lines of flux. ... Ultraviolet-Visible Spectroscopy or Ultraviolet-Visible Spectrophotometry (UV/ VIS) involves the spectroscopy of photons (spectrophotometry). ... Infrared spectroscopy (IR Spectroscopy) is the subset of spectroscopy that deals with the IR region of the EM spectrum. ... It has been suggested that NMR Data Processing be merged into this article or section. ... Mass spectrometry (also known as mass spectroscopy (deprecated)[1] or in common speech mass-spec) is an analytical technique used to measure the mass-to-charge ratio of ions. ... “Multivalent” redirects here. ... “Multivalent” redirects here. ... Ruthenium tetroxide (RuO4) is a yellow, diamagnetic tetrahedral ruthenium compound. ... In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals) and 25 degrees Celsius (298. ... A chemical compound is a chemical substance consisting of two or more different chemically bonded chemical elements, with a fixed ratio determining the composition. ... General Name, Symbol, Number osmium, Os, 76 Chemical series transition metals Group, Period, Block 8, 6, d Appearance silvery, blue cast Atomic mass 190. ...

Physical properties

Pure osmium tetroxide is colorless, but it is usually contaminated by a small amount of yellow-brown osmium dioxide (OsO₂), giving it a yellowish hue. OsO₄ is soluble in carbon tetrachloride (CCl₄) and moderately soluble in water, with which it reacts reversibly to form osmic acid (see below). OsO₄ is volatile: it sublimes at room temperature. It has a characteristic odor similar to ozone. In fact, the element name osmium is derived from osme, Greek for odor.^[1] R-phrases , , , , S-phrases , , , , , Flash point non flammable RTECS number FG4900000 Supplementary data page Structure and properties n, εr, etc. ... Sublimation of an element or substance is a conversion between the solid and the gaseous phases of matter, with no intermediate liquid stage. ... Room temperature describes a certain temperature within enclosed space that is uses for various purposes by human beings. ... For other uses, see Ozone (disambiguation). ... The periodic table of the chemical elements A chemical element, or element for short, is a type of atom that is defined by its atomic number; that is, by the number of protons in its nucleus. ...

Structure and electron configuration

As a d⁰ metal, Os(VIII) is expected to adopt a tetrahedral geometry when bound to four ligands. Tetrahedral structures are seen for MnO₄^- and CrO₄^2-. Image File history File links Size of this preview: 356 × 316 pixelsFull resolution (356 × 316 pixel, file size: 7 KB, MIME type: image/png) I, Smokefoot, created this and release it with all rights. ... The structure of the permanganate anion A permanganate is a chemical compound that contains the permanganate ion (MnO4−). Because manganese is in the +7 oxidation state, the permanganate ion is a strong oxidizer. ... A sample of ammonium dichromate Chromates and dichromates are salts of chromic acid and dichromic acid, respectively. ...

The osmium of OsO₄ has a formal oxidation state of 8+, the highest oxidation state for a transition metal. The osmium atom has eight valence electrons. If one assumes that two electrons are donated by each of the four oxide ligands, the total electron count for the complex is 16, as also seen for permanganate and chromate. General Name, Symbol, Number osmium, Os, 76 Chemical series transition metals Group, Period, Block 8, 6, d Appearance silvery, blue cast Atomic mass 190. ... In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. ... In chemistry, the term transition metal (sometimes also called a transition element) has two possible meanings: It commonly refers to any element in the d-block of the periodic table, including zinc, cadmium and mercury. ... The valence shell is the outermost shell of an atom, which contains the electrons most likely to account for the nature of any reactions involving the atom and of the bonding interactions it has with other atoms. ... An oxide is a chemical compound containing an oxygen atom and other elements. ... The structure of the permanganate anion A permanganate is a chemical compound that contains the permanganate ion (MnO4−). Because manganese is in the +7 oxidation state, the permanganate ion is a strong oxidizer. ... A sample of ammonium dichromate Chromates and dichromates are salts of chromic acid and dichromic acid, respectively. ...

Synthesis

OsO₄ is formed slowly when osmium powder reacts with O₂ at 298 K. Reaction of bulk solid requires heating to 670 K.^[2]

Os + 2 O₂ → OsO₄

Reactions

Oxofluorides

Osmium forms several oxofluorides, all of which are very sensitive to moisture. Purple cis-OsO₂F₄ forms at 77 K in an aqueous solution of HF^[3]:

OsO₄ + 2 KrF₂ → cis-OsO₂F₄ + 2 Kr + O₂

OsO₄ also reacts with F₂ to form yellow OsO₃F₂:

2 OsO₄ + 2 F₂ → 2 OsO₃F₂ + O₂

OsO₄ reacts with one equivalent of [Me₄N]F at 298 K and 2 equivalents at 253 K^[4]:

OsO₄ + [Me₄N]F → [Me₄N][OsO₄F]

OsO₄ + 2 [Me₄N]F → [Me₄N]₂[cis-OsO₄F₂]

Oxidation of alkenes

OsO₄ catalyzes the cis-dihydroxylation of alkenes by hydrogen peroxide or related sources of oxygen atoms in the presence of water. The reaction that is catalyzed is:

R₂C=CR₂ + H₂O₂ → R₂C(OH)-C(OH)R₂

In terms of mechanism, Os^VIIIO₄ adds to alkenes R₂C=CR₂ to afford cyclic "esters" R₄C₂O₂Os^VIO₂, which undergo hydrolysis to give the vicinal diol and release a reduced osmium oxide (Os^VI): In chemistry vicinal stands for any two functional groups bonded to two adjacent carbon atoms. ... A diol is a chemical compound containing two hydroxyl groups (-OH groups). ...

Lewis bases such as tertiary amines and pyridines increase the reaction rate. This "ligand-acceleration" arises via the formation of adduct OsO₄L, which adds more rapidly to the alkene. If the amine is chiral, then the dihydroxylation can proceed with enantioselectivity (see Sharpless asymmetric dihydroxylation). Image File history File links Size of this preview: 548 × 177 pixelsFull resolution (548 × 177 pixel, file size: 7 KB, MIME type: image/gif) I, the creator of this work, hereby release it into the public domain. ... The general structure of an amine Amines are organic compounds and a type of functional group that contain nitrogen as the key atom. ... Pyridine is a chemical compound with the formula C5H5N. It is a liquid with a distinctively putrid odour. ... Wikipedia does not yet have an article with this exact name. ... Sharpless asymmetric dihydroxylation (also called the Sharpless bishydroxylation) is the chemical reaction of an alkene with osmium tetroxide in the presence of a chiral quinine ligand to form a vicinal diol. ...

Since OsO₄ is toxic and expensive, it is used in catalytic amounts. The osmium catalyst is regenerated by oxidizing agents, such as H₂O₂, N-methylmorpholine N-oxide (NMO, see Upjohn dihydroxylation), and K₃Fe(CN)₆. These oxidizing reagents do not react with the alkenes on their own. It has been suggested that this article or section be merged into Catalysis. ... Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colourless in a dilute solution, slightly more viscous than water. ... N-methylmorpholine-N-Oxide or NMO is an organic compound. ... Upjohn dihydroxylation is an organic reaction converting an alkene to a bis hydroxide developed by V. VanRheenen, R. C. Kelly and D. Y. Cha of the Upjohn Company, USA in 1976. ... Potassium ferricyanide (K3[Fe(CN)6]) also known as red prussiate, Prussian red or potassium hexacyanoferrate(III), is a coordination compound that is stable at room temperature and pressure and forms ruby red crystals and powder. ...

Miscellaneous reactions

OsO₄ dissolves in alkaline aqueous solution to give the osmate anion:

OsO₄ + 2 NaOH → Na₂[cis-OsO₄(OH)₂] + O₂

OsO₄ is Lewis acidic, and when the Lewis bases are amines, the oxides can undergo substitution. Thus with NH₃ one obtains the nitrido-oxide: Ammonia is a compound with the formula NH3. ...

OsO₄ + NH₃ + KOH → K[Os(N)O₃] + 2 H₂O

The [Os(N)O₃]^- anion is isoelectronic and isostructural with OsO₄. Using primary amine tert-BuNH₂ one obtains the corresponding imido derivative:

OsO₄ + 4 Me₃CNH₂ → Os(NCMe₃)₄ + 4 H₂O

OsO₄ undergoes "reductive carbonylation" in methanol at 400 K and 200 bar of pressure to produce the triangular cluster Os₃(CO)₁₂:

3 OsO₄ + 24 CO → Os₃(CO)₁₂ + 12 CO₂^[5]

In this reaction osmium changes oxidation state by eight units. Carbon monoxide, with the chemical formula CO, is a colorless, odorless, and tasteless gas. ...

Uses

Organic synthesis

In organic synthesis OsO₄ is widely used to oxidise alkenes to the vicinal diols, adding two hydroxyl groups at the same side (syn addition). See reaction and mechanism above. This mechanism has been made both catalytic (Upjohn dihydroxylation) and asymmetric (Sharpless asymmetric dihydroxylation, named after Nobel Laureate K. Barry Sharpless).^[6] The chemical structure of ethylene, the simplest alkene. ... // Hydroxyl group The term hydroxyl group is used to describe the functional group -OH when it is a substituent in an organic compound. ... Ethylene undergoing syn and anti addition In organic chemistry, syn addition is the addition of two substituents to the same side (or face) of a double bond or triple bond, resulting in a decrease in bond order but an increase in number of substituents. ... Upjohn dihydroxylation is an organic reaction converting an alkene to a bis hydroxide developed by V. VanRheenen, R. C. Kelly and D. Y. Cha of the Upjohn Company, USA in 1976. ... Sharpless asymmetric dihydroxylation (also called the Sharpless bishydroxylation) is the chemical reaction of an alkene with osmium tetroxide in the presence of a chiral quinine ligand to form a vicinal diol. ... Karl Barry Sharpless (born April 28, 1941) is an American chemist renowned for his work on organometallic chemistry. ...

Osmium tetroxide is also used in catalytic amount in the Sharpless oxyamination to give vicinal amino-alcohols. The Sharpless oxyamination (often known as Sharpless aminohydroxylation) is the chemical reaction of alkenes with alkyl imido osmium compounds to form vicinal amino-alcohols. ...

Biological staining

OsO₄ is a widely used staining agent used in transmission electron microscopy (TEM) to provide contrast to the image. As a lipid stain, it is also useful in scanning electron microscopy (SEM) as an alternative to sputter coating. It embeds a heavy metal directly into cell membranes, creating a high secondary electron emission without the need for coating the membrane with a layer of metal, which can obscure details of the cell membrane. Additionally, Osmium tetroxide is also used for fixing biological samples in conjunction with HgCl₂. Its rapid killing abilities are used to quickly kill specimen like protozoa. Osmium tetroxide is also used as a stain for lipids in optical microscopy. OsO₄ also stains the human cornea (see safety considerations). ... Transmission electron microscopy (TEM) is an imaging technique whereby a beam of electrons is focused onto a specimen causing an enlarged version to appear on a fluorescent screen or layer of photographic film (see electron microscope), or can be detected by a CCD camera. ... A polyunsaturated triglyceride. ... Low temperature SEM magnification series for a snow crystal. ... Sputter coating in microscopy is a process of covering a specimen with a very thin layer of heavy metal, generally a gold/palladium (Au/Pd) mixture. ... e- redirects here. ... The chemical compound osmium tetroxide (OsO4), also known as osmium tetraoxide, osmium(VIII) oxide, or osmic acid, is an oxide of the element osmium. ...

Osmeth

OsO₄ can be recycled and stored in the form of osmeth, a golden crystalline solid. Osmeth is OsO₄ complexed with hexamine and does not emit toxic fumes as opposed to pure OsO₄. It can be dissolved in tetrahydrofuran (THF) and diluted in an aqueous buffer solution to make a dilute (0.25%) working solution of OsO₄.^[7] Hexamethylenetetramine cage Hexamine ((CH2)6N4) is a chemical created by the reaction of 6 moles of formaldehyde and 4 moles of ammonia. ... For other uses of THF, see THF (disambiguation) Tetrahydrofuran is a heterocyclic organic compound. ... Acids and bases: Acid-base reaction theories pH Self-ionization of water Buffer solutions Systematic naming Electrochemistry Acid-base extraction Acids: Strong acids Weak acids Superacids Lewis acids Mineral acids Organic acids Bases: Strong bases Weak bases Superbases Lewis bases Organic bases edit Buffer solutions are solutions which resist change... Dissolving table salt (NaCl) in water This article is about a chemical solution; for other uses of the term solution, see solution (disambiguation). ...

Osmium ore refining

OsO₄ is an intermediate in osmium ore refining. Osmium residues are reacted with Na₂O₂ forming [OsO₄(OH)₂]^2- anions, which, when reacted with chlorine (Cl₂) gas and heated, form OsO₄. The oxide is dissolved in alcoholic NaOH forming [OsO₂(OH)₄]^2- anions, which, when reacted with NH₄Cl, forms OsO₂Cl₂(NH₄)₄. This is ignited under hydrogen (H₂) gas leaving behind pure osmium (Os).^[8] General Name, Symbol, Number chlorine, Cl, 17 Chemical series halogens Group, Period, Block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... Sodium hydroxide (NaOH), also known as caustic soda or lye in North America, is a caustic metallic base used in industry (mostly as a strong chemical base) in the manufacture of paper, textiles, and detergents. ... Ammonium chloride or Sal Ammoniac (chemically ammonium chloride (NH4Cl); also nushadir salt, zalmiak, sal armagnac, sal armoniac, salmiakki, salmiak and salt armoniack) is, in its pure form, a clear white water-soluble crystalline salt with a biting taste. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ...

Buckminsterfullerene adduct

OsO₄ allowed for the confirmation of the soccer ball model of buckminsterfullerene, a 60 atom carbon allotrope. The adduct, formed from a derivative of OsO₄, was C₆₀(OsO₄)(4-tert-butylpyridine)₂. The adduct broke the fullerene's symmetry allowing for crystallization and confirmation of the structure of C₆₀ by x-ray crystallography^[9] Buckminsterfullerene (C60) Fullerenes are molecules composed entirely of carbon, taking the form of a hollow sphere, ellipsoid, or tube. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Standard atomic weight 12. ... Allotropy (Gr. ... In organic chemistry, butyl is a four-carbon alkyl substituent with chemical formula -C4H9. ... Pyridine is a chemical compound with the formula C5H5N. It is a liquid with a distinctively putrid odour. ... X-ray crystallography or single-crystal X-ray diffraction is an analytical technique which uses the diffraction pattern produced by bombarding a single crystal with X-rays to solve the crystal structure. ...

Safety considerations

OsO₄ is highly poisonous, even at low exposure levels, and must be handled with appropriate precautions. In particular, inhalation at concentrations well below those at which a smell can be perceived can lead to pulmonary edema, and subsequent death. Noticeable symptoms can take hours to appear after exposure. OsO₄ also stains the human cornea, which can lead to blindness if proper safety precautions are not observed. Pulmonary edema is swelling and/or fluid accumulation in the lungs. ... The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eyes optical power [1]. Together with the lens, the cornea refracts light and, as a result, helps the eye to focus. ...

On the 6th of April 2004 the American news organization ABC News reported that British intelligence sources believed they had foiled a plot to detonate a bomb involving OsO₄.

External links

• International Chemical Safety Card 0528
• NIOSH Pocket Guide to Chemical Hazards
• BBC report on bomb plot
• BBC What is Osmium tetroxide article
• Osmium Tetroxide: Molecule of the Month
• Chemical Reactions

• Links to external chemical sources

References

• Cotton, S. A. "Chemistry of Precious Metals," Chapman and Hall (London): 1997. ISBN 0-7514-0413-6.
• Berrisford, D. J.; Bolm, C.; Sharpless, K. B., "Ligand Accelerated Catalysis", Angewandte Chemie, International Edition English, 1995, volume 34, pp. 1059-1070.

1. ^ Dr. M Thomson, Osmium tetroxide(OsO₄). [1]
2. ^ Housecroft & Sharpe. "Inorganic Chemistry". (ed 2, 2005). p 671-673
3. ^ Christe et al. Osmium Tetrafluoride Dioxide, cis-OsO₂F₄. J. Am. Chem. Soc. 1993, 115. 11279-11284
4. ^ Housecroft & Sharpe. "Inorganic Chemistry". (ed 2, 2005). p 671-673
5. ^ Housecroft & Sharpe. "Inorganic Chemistry". (ed 2, 2005). p 672,710
6. ^ Sharpless, K. B.; "Searching for New Reactivity (Nobel Lecture)".Angew. Chem. Int. Ed. 2002, 41, 2024-2032
7. ^ Kiernan, J.A. Department of Anatomy & Cell Biology, The University of Western Ontario. [2]
8. ^ Dr. M Thomson, Osmium tetroxide(OsO₄). [3]
9. ^ Hawkins et al."Crystal Structure of Osmylated C₆₀ : Confirmation of the Soccer Ball Framework". Science, New Series, Vol. 252, No. 5003. (Apr. 12, 1991), pp. 312-313. [4]