| Revision as of 12:17, 18 September 2011 editZéroBot (talk | contribs)704,777 editsm r2.7.1) (Robot: Adding es:Tetróxido de osmio← Previous edit |
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| ImageFileL1 = Osmium-tetroxide-2D-dimensions.png |
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| verifiedrevid = 451133444 |
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| ImageSizeL1 = 130 px |
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| ImageFileL1 = Osmium-tetroxide-2D-dimensions.svg |
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| ImageSizeL1 = 130px |
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| ImageNameL1 = Stick model osmium tetroxide |
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| ImageNameL1 = Stick model osmium tetroxide |
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| ImageFileR1 = Osmium-tetroxide-ED-3D-balls-A.png |
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| ImageFileR1 = Osmium-tetroxide-ED-3D-balls-A.png |
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| ImageNameR1 = Ball and stick model of osmium tetroxide |
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| ImageNameR1 = Ball and stick model of osmium tetroxide |
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| ImageFile2 = Osmium tetroxide 0.1 gram in ampoule.jpg |
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| ImageFile2 = Osmium tetroxide.jpg |
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| ImageSize2 = 300px |
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| ImageSize2 = 270px |
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| PIN = Osmium tetraoxide |
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| PIN = Osmium tetraoxide |
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| SystematicName = Tetraoxoosmium |
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| SystematicName = Tetraoxoosmium |
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| OtherNames = Osmium(VIII) oxide |
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| OtherNames = Osmium(VIII) oxide |
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| Section1 = {{Chembox Identifiers |
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|Section1={{Chembox Identifiers |
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| InChI1 = 1/4O.Os/rO4Os/c1-5(2,3)4 |
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| InChI1 = 1/4O.Os/rO4Os/c1-5(2,3)4 |
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| InChIKey1 = VUVGYHUDAICLFK-TYHKRQCIAE |
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| InChIKey1 = VUVGYHUDAICLFK-TYHKRQCIAE |
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| CASNo = 20816-12-0 |
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| CASNo = 20816-12-0 |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| UNII = P40W033BGM |
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| PubChem = 30318 |
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| PubChem = 30318 |
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| PubChem_Ref = {{Pubchemcite}} |
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| PubChem1 = 56370778 |
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| PubChem1_Comment = (monopotassiate) |
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| PubChem1_Ref = {{Pubchemcite}} |
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| PubChem2 = 75811001 |
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| PubChem2_Comment = (monoquinuclidiniate) |
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| PubChem2_Ref = {{Pubchemcite}} |
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| PubChem3 = 53113021 |
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| PubChem3_Comment = (monotemediate) |
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| PubChem3_Ref = {{Pubchemcite}} |
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| ChemSpiderID = 28158 |
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| ChemSpiderID = 28158 |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChEBI_Ref = {{ebicite|correct|EBI}} |
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| ChEBI = 88215 |
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| EINECS = 244-058-7 |
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| EINECS = 244-058-7 |
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| UNNumber = UN 2471 |
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| UNNumber = UN 2471 |
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| InChI = 1S/4O.Os |
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| InChI = 1S/4O.Os |
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| InChIKey = VUVGYHUDAICLFK-UHFFFAOYSA-N}} |
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| InChIKey = VUVGYHUDAICLFK-UHFFFAOYSA-N}} |
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| Section2 = {{Chembox Properties |
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|Section2={{Chembox Properties |
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| Formula = OsO<sub>4</sub> |
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| Formula = OsO<sub>4</sub> |
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| MolarMass = 254.23 g/mol |
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| MolarMass = 254.23{{nbsp}}g/mol |
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| Appearance = pale yellow solid |
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| Appearance = White volatile solid |
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| Odor = Acrid, chlorine-like |
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| Density = 4.91 g/cm<sup>3</sup><ref name="Merck-SDB"> (at 20 °C)</ref> |
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| Density = 4.9{{nbsp}}g/cm<sup>3</sup><ref>{{ cite web | url = http://www.inchem.org/documents/icsc/icsc/eics0528.htm | publisher = InChem | title = Osmium tetroxide ICSC: 0528 }}</ref> |
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| MeltingPt = 40.25 °C |
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| BoilingPt = 129.7 °C |
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| MeltingPtC = 40.25 |
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| BoilingPtC = 129.7<ref>{{cite journal |last1=Koda |first1=Yoshio |date=1986 |title=Boiling Points and Ideal Solutions of Ruthenium and Osmium Tetraoxides |url= |journal=Journal of the Chemical Society, Chemical Communications |volume=1986 |issue=17 |pages=1347–1348 |doi=10.1039/C39860001347 |access-date=}}</ref> |
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| Solubility = 65 g/L<ref name="Merck-SDB"/> |
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| Solubility = 5.70{{nbsp}}g/100{{nbsp}}mL (10 °C) <br />6.23{{nbsp}}g/100{{nbsp}}mL (25 °C) |
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| SolubleOther = soluble in most ] |
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| Solvent1 = carbon tetrachloride{{!}}CCl<sub>4</sub> |
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| pKa = |
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| Solubility1 = 375{{nbsp}}g/100{{nbsp}}mL |
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| SolubleOther = Soluble in most organic solvents, ], ] |
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| pKa = |
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| VaporPressure = 7{{nbsp}}mmHg (20 °C)<ref name=PGCH/> |
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| Section3 = {{Chembox Structure |
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|Section3={{Chembox Structure |
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| Structure_ref = <ref name=s1>{{ cite journal |author1=Krebs, B. |author2=Hasse, K. D. | title = Refinements of the Crystal Structures of KTcO<sub>4</sub>, KReO<sub>4</sub> and OsO<sub>4</sub>. The Bond Lengths in Tetrahedral Oxo-Anions and Oxides of d<sup>0</sup> Transition Metals | journal = Acta Crystallographica B | year = 1976 | volume = 32 | issue = 5 | pages = 1334–1337 | doi = 10.1107/S056774087600530X |bibcode=1976AcCrB..32.1334K }}</ref> |
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| CrystalStruct = Monoclinic, ] |
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| CrystalStruct = Monoclinic, ] |
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| SpaceGroup = C2/c |
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| SpaceGroup = C2/c; a = 0.4515 nm, b = 0.52046 nm, c = 0.80838 nm, α = 77.677°, β = 73.784°, γ = 64.294°<ref name=s1>{{cite journal| journal = Acta Crystallographica B| year = 1976| volume = 32 | pages = 1334–1337| |
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| LattConst_a = 9.379 ] |
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title = Refinements of the Crystal Structures of KTcO4, KReO4 and OsO4. The Bond Lengths in Tetrahedral Oxo-Anions and Oxides of d0 Transition Metals| authors = Krebs B., Hasse K.D.|doi=10.1107/S056774087600530X}}</ref> |
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| LattConst_b = 4.515 ] |
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| LattConst_c = 8.630 ] |
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| LattConst_beta = 116.58 |
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| UnitCellVolume = 326.8 Å<sup>3</sup> |
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| UnitCellFormulas = 4 |
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| MolShape = tetrahedral |
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| Section7 = {{Chembox Hazards |
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|Section7={{Chembox Hazards |
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| ExternalMSDS = |
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| ExternalSDS = |
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| GHSPictograms = {{GHS05}}{{GHS06}} |
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| EUIndex = 076-001-00-5 |
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| GHSSignalWord = Danger |
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| EUClass = Very toxic ('''T+''')<br/>Corrosive ('''C''') |
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| RPhrases = {{R26/27/28}}, {{R34}} |
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| HPhrases = {{H-phrases|300|310|314|330}} |
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| PPhrases = {{P-phrases|260|262|264|270|271|280|284|301+310|301+330+331|302+350|303+361+353|304+340|305+351+338|310|320|321|322|330|361|363|403+233|405|501}} |
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| SPhrases = {{S1/2}}, {{S7/9}}, {{S26}}, {{S45}} |
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| NFPA-H = 4 |
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| NFPA-H = 3 |
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| NFPA-F = 0 |
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| NFPA-F = 0 |
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| NFPA-R = 1 |
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| NFPA-R = 1 |
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| NFPA-O = OX |
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| NFPA-S = OX |
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| IDLH = 1 mg/m<sup>3</sup><ref name=PGCH>{{PGCH|0473}}</ref> |
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| REL = TWA 0.002{{nbsp}}mg/m<sup>3</sup> (0.0002{{nbsp}}ppm) ST 0.006{{nbsp}}mg/m<sup>3</sup> (0.0006{{nbsp}}ppm)<ref name=PGCH/> |
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| PEL = TWA 0.002{{nbsp}}mg/m<sup>3</sup><ref name=PGCH/> |
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| LCLo = 1316{{nbsp}}mg/m<sup>3</sup> (rabbit, 30{{nbsp}}min)<br/>423{{nbsp}}mg/m<sup>3</sup> (rat, 4{{nbsp}}hr)<br/>423{{nbsp}}mg/m<sup>3</sup> (mouse, 4{{nbsp}}hr)<ref>{{IDLH|20816120|Osmium tetroxide (as Os)}}</ref> |
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| Section8 = {{Chembox Related |
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| OtherAnions = |
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| OtherAnions = |
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| OtherCations = ] |
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| OtherCations = ]<br />] |
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| OtherFunctn = ] |
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| OtherFunction = ] |
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| Function = ] ]s |
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| OtherFunction_label = ] ]s |
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| OtherCpds = |
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'''Osmium tetroxide''' (also called '''osmium tetraoxide''') is the ] with the ] OsO<sub>4</sub>. The compound is noteworthy for its many uses, despite the rarity of ]. It also has a number of interesting properties, one being that the solid is ]. |
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'''Osmium tetroxide''' (also '''osmium(VIII) oxide''') is the ] with the ] OsO<sub>4</sub>. The compound is noteworthy for its many uses, despite its toxicity and the rarity of ]. It also has a number of unusual properties, one being that the solid is ]. The compound is colourless, but most samples appear yellow.<ref>{{cite journal | last1 = Girolami | first1 = Gregory | year = 2012 | title = Osmium weighs | journal = Nature Chemistry | volume = 4 | issue = 11| page = 954 | doi = 10.1038/nchem.1479 | pmid = 23089872 | bibcode = 2012NatCh...4..954G | doi-access = free }}</ref> This is most likely due to the presence of the impurity ], which is yellow-brown in colour.<ref>Cotton and Wilkinson, Advanced Inorganic Chemistry, p.1002</ref> In biology, its property of binding to lipids has made it a widely-used stain in electron microscopy. |
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==Physical properties== |
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==Physical properties== |
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Osmium tetroxide exists as a pale yellow-brown crystalline solid (] crystal symmetry<ref name=s1/>) with a characteristic acrid ]-like odor.<ref name=niosh/> The ] name osmium is derived from ''osme'', ] for ''odor''. OsO<sub>4</sub> is volatile: it ] at ]. It is soluble in a wide range of organic solvents, and moderately soluble in water, with which it reacts reversibly to form osmic acid (see below).<ref name = thomson>{{cite web|author = Mike Thompson|publisher = ]|title = Osmium tetroxide (OSO<sub>4</sub>)|url = http://www.chm.bris.ac.uk/motm/oso4/oso4h.htm|accessdate = 2007-08-24}}</ref> ''Pure'' osmium tetroxide is probably colourless<ref>{{cite book|author1=Ian S. Butler|author2=John Frank Harrod|title=Inorganic chemistry: principles and applications|url=http://books.google.com/books?id=Nd3vAAAAMAAJ|accessdate=21 June 2011|year=1989|publisher=Benjamin/Cummings|isbn=9780805302479|page=343}}</ref> and it has been suggested that its yellow hue is due to ] (OsO<sub>2</sub>) impurities<ref>{{cite book|author=Cotton|title=Advanced Inorganic Chemistry, 6Th Ed|url=http://books.google.com/books?id=U3MWRONWAmMC|accessdate=21 June 2011|date=31 August 2007|publisher=Wiley India Pvt. Ltd.|isbn=9788126513383|page=1002}}</ref> although osmium dioxide normally exists as a black powder.<ref>{{cite web| url = http://www.alfa.com/content/msds/USA/39497.pdf|title = Alfa Aesar MSDS| accessdate = 2010-10-25}}</ref> Osmium tetroxide molecule is tetrahedral and therefore non-polar. This nonpolarity helps OsO<sub>4</sub> penetrate charged cell membranes. OsO<sub>4</sub> is 518 times more soluble in CCl<sub>4</sub> than in water. |
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Osmium(VIII) oxide forms ] crystals.<ref name=s1/><ref name=niosh/> It has a characteristic acrid ]-like odor. The ] name osmium is derived from ''osme'', ] for ''odor''. OsO<sub>4</sub> is volatile: it ] at ]. It is soluble in a wide range of organic solvents. It is moderately soluble in water, with which it reacts reversibly to form osmic acid (see below).<ref name=thompson>{{ cite web | author = Thompson, M. | publisher = ] | title = Osmium tetroxide (OsO<sub>4</sub>) | url = http://www.chm.bris.ac.uk/motm/oso4/oso4h.htm | access-date = 2012-04-07 }}</ref> ''Pure'' osmium(VIII) oxide is probably colourless;<ref>{{ cite book |author1=Butler, I. S. |author2=Harrod, J. F. | title = Inorganic Chemistry: Principles and Applications | year = 1989 | publisher = Benjamin / Cummings | isbn = 978-0-8053-0247-9 | page = 343 | url = https://books.google.com/books?id=Nd3vAAAAMAAJ | access-date= 2012-04-07 }}</ref> it has been suggested that its yellow hue is attributable due to ] (OsO<sub>2</sub>) impurities.<ref>{{ cite book | author = Cotton, F. A. | title = Advanced Inorganic Chemistry | edition = 6th | url = https://books.google.com/books?id=U3MWRONWAmMC | year = 2007 | publisher = J. Wiley | location = New Delhi, India | isbn = 978-81-265-1338-3 | page = 1002 }}</ref> The osmium tetroxide molecule is tetrahedral and therefore nonpolar. This nonpolarity helps OsO<sub>4</sub> penetrate charged cell membranes. |
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==Structure and electron configuration== |
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==Structure and electron configuration== |
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The ] of OsO<sub>4</sub> has an ] of VIII; however, the metal does not possess a corresponding 8+ charge as the bonding in the compound is largely ] in character (the ] required to produce a formal 8+ charge also far exceeds the energies available in normal chemical reactions). The osmium atom exhibits double bonds to the four ] ], resulting in a ]. OsO<sub>4</sub> is isoelectronic with ] and ] ions. |
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]With a d<sup>0</sup> configuration, Os(VIII) is expected to form tetrahedral complexes when bound to four ligands. Tetrahedral structures are seen for the electronically related oxides ] and ]. |
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The ] of OsO<sub>4</sub> has a formal ] of +8, the highest oxidation state known for a ]. The osmium atom has eight ] electrons. If one assumes that two electrons are donated by each of the four ] ligands, the total electron count for the complex is 16, as also seen for the isoelectronic species ] and ]. |
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The high oxidation state of osmium in this compound can be rationalized by comparison of main-group and transition-metal chemistry. Just as the elements in groups 3 through 7 form compounds analogous to those formed by elements in groups 13 through 17 (e.g. TiCl<sub>4</sub> and GeCl<sub>4</sub>, VF<sub>5</sub> and AsF<sub>5</sub>, CrO<sub>4</sub><sup>2−</sup> and SeO<sub>4</sub><sup>2−</sup>, etc.), we might expect the elements in group 8 to form compounds analogous to those formed by the noble gases. This is the case, as demonstrated by the existence of compounds like OsO<sub>4</sub> and ]. |
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==Synthesis== |
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==Synthesis== |
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OsO<sub>4</sub> is formed slowly when osmium powder reacts with O<sub>2</sub> at ambient temperature. Reaction of bulk solid requires heating to 400 °C.<ref name = h&s>{{Housecroft2nd|pages=671–673, 710}}</ref> |
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OsO<sub>4</sub> is formed slowly when osmium powder reacts with O<sub>2</sub> at ambient temperature. Reaction of bulk solid requires heating to 400 °C.<ref name = h&s>{{Housecroft2nd|pages=671–673, 710}}</ref> |
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:Os + 2 O<sub>2</sub> → OsO<sub>4</sub> |
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:<chem>Os + 2O2 -> OsO4</chem> |
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==Reactions== |
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==Reactions== |
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===Oxofluorides=== |
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Osmium forms several oxofluorides, all of which are very sensitive to moisture. |
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Purple ''cis''-OsO<sub>2</sub>F<sub>4</sub> forms at 77 K in an anhydrous ] solution:<ref>{{cite journal|author = K. O. Christe, D. A. Dixon, H. G. Mack, H. Oberhammer, A. Pagelot, J. C. P. Sanders and G. J. Schrobilgen|title = Osmium tetrafluoride dioxide, cis-OsO<sub>2</sub>F<sub>4</sub>|year = 1993|journal = ]|volume = 115|issue = 24|pages = 11279–11284|doi = 10.1021/ja00077a029}}</ref> |
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: OsO<sub>4</sub> + 2 KrF<sub>2</sub> → ''cis''-OsO<sub>2</sub>F<sub>4</sub> + 2 Kr + O<sub>2</sub> |
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===Oxidation of alkenes=== |
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OsO<sub>4</sub> also reacts with F<sub>2</sub> to form yellow OsO<sub>3</sub>F<sub>2</sub>:<ref name=chem>{{cite book| author = Cotton, S. A.| title = Chemistry of Precious Metals| publisher = Chapman and Hall| location= London| year = 1997| isbn = 0-7514-0413-6}}</ref> |
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Alkenes add to OsO<sub>4</sub> to give ] species that hydrolyze to ''cis''-diols. The net process is called dihydroxylation. This proceeds via a ] reaction between the OsO<sub>4</sub> and alkene to form an intermediate osmate ester that rapidly hydrolyses to yield the ]. As the oxygen atoms are added in a concerted step, the resulting stereochemistry is '']''. |
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: 2 OsO<sub>4</sub> + 2 F<sub>2</sub> → 2 OsO<sub>3</sub>F<sub>2</sub> + O<sub>2</sub> |
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OsO<sub>4</sub> is expensive and highly toxic, making it an unappealing reagent to use in ] amounts. However, its reactions are made ] by adding ]s to reoxidise the Os(VI) by-product back to Os(VIII). Typical reagents include ] (]), ] (]) and ]/water. These reoxidants do not react with the alkenes on their own. Other osmium compounds can be used as catalysts, including osmate(VI) salts (<sup>2−</sup>, and osmium trichloride hydrate (OsCl<sub>3</sub>·''x''H<sub>2</sub>O). These species oxidise to osmium(VIII) in the presence of such oxidants.<ref>{{ cite journal | title = On the timing of hydrolysis / reoxidation in the osmium-catalyzed asymmetric dihydroxylation of olefins using potassium ferricyanide as the reoxidant |author1=Ogino, Y. |author2=Chen, H. |author3=Kwong, H.-L. |author4=Sharpless, K. B. | journal = ] | year = 1991 | volume = 32 | issue = 32 | pages = 3965–3968 | doi = 10.1016/0040-4039(91)80601-2 }}</ref> |
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OsO<sub>4</sub> reacts with one equivalent of F at 298 K and 2 equivalents at 253 K:<ref name = h&s/> |
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Lewis bases such as tertiary ]s and ]s increase the rate of dihydroxylation. This "ligand-acceleration" arises via the formation of ] OsO<sub>4</sub>L, which adds more rapidly to the alkene. If the amine is chiral, then the dihydroxylation can proceed with enantioselectivity (see ]).<ref name=catalysis>{{ cite journal |author1=Berrisford, D. J. |author2=Bolm, C. |author3=Sharpless, K. B. | title = Ligand-Accelerated Catalysis | year = 1995 | journal = ] | volume = 34 | issue = 10 | pages = 1059–1070 | doi = 10.1002/anie.199510591 }}</ref> OsO<sub>4</sub> does not react with most carbohydrates.<ref name=stain/> |
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: OsO<sub>4</sub> + F → |
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The process can be extended to give two ]s in the ], which uses ] to achieve ] and to regenerate the catalytic loading of OsO<sub>4</sub>. This process is equivalent to that of ]. |
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: OsO<sub>4</sub> + 2 F → <sub>2</sub> |
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:] |
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===Oxidation of alkenes=== |
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OsO<sub>4</sub> 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<ref name=catalysis>{{cite journal|author = D. J. Berrisford, C. Bolm and K. B. Sharpless|title = Ligand-Accelerated Catalysis|year = 1995|journal = ]|volume = 34|issue = 10|pages = 1059–1070|doi = 10.1002/anie.199510591}}</ref> |
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:R<sub>2</sub>C=CR<sub>2</sub> + H<sub>2</sub>O<sub>2</sub> → R<sub>2</sub>C(OH)-C(OH)R<sub>2</sub>. |
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===Coordination chemistry=== |
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In terms of mechanism, Os<sup>VIII</sup>O<sub>4</sub> adds to alkenes R<sub>2</sub>C=CR<sub>2</sub> to afford cyclic "esters" R<sub>4</sub>C<sub>2</sub>O<sub>2</sub>Os<sup>VI</sup>O<sub>2</sub>, which undergo hydrolysis to give the ] ] and release a reduced osmium oxide (Os<sup>VI</sup>): |
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<sup>+</sup><sup>–</sup>, OsO(NBu<sup>t</sup>)(2,4,6-Me<sub>3</sub>C<sub>6</sub>H<sub>2</sub>)<sub>2</sub>, OsO<sub>3</sub>(NBu<sup>t</sup>), and ReO<sub>3</sub>|author=Brian S. McGilligan |author2=John Arnold |author3=Geoffrey Wilkinson |author4=Bilquis Hussain-Bates |author5=Michael B. Hursthouse |journal=J. Chem. Soc., Dalton Trans.|year=1990|issue=8|pages=2465–2475 |doi=10.1039/DT9900002465}}</ref>]]OsO<sub>4</sub> is a ] and a mild oxidant. It reacts with alkaline ] to give the perosmate anion {{chem|OsO|4|(OH)|2|2−}}.<ref>{{Greenwood&Earnshaw2nd}}</ref> This species is easily reduced to ] anion, {{chem|OsO|2|(OH)|4|2-}}. |
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Lewis bases such as tertiary ]s and ]s increase the reaction rate. This "ligand-acceleration" arises via the formation of ] OsO<sub>4</sub>L, which adds more rapidly to the alkene. If the amine is chiral, then the dihydroxylation can proceed with enantioselectivity (see ]).<ref name=catalysis/> |
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When the ] is an ], adducts are also formed. Thus OsO<sub>4</sub> can be stored in the form of '''osmeth''', in which OsO<sub>4</sub> is ] with ]. Osmeth can be dissolved in ] (THF) and diluted in an aqueous ] to make a dilute (0.25%) working ] of OsO<sub>4</sub>.<ref>{{ cite web | author = Kiernan, J. A. | publisher = Department of Anatomy & Cell Biology, The University of Western Ontario | url = http://www.histosearch.com/histonet/Nov00A/Re.quotDisposalquotofOsmi.html | title = Re: "Disposal" of Osmium Tetroxide "Waste" }}</ref> |
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OsO<sub>4</sub> is used in catalytic amounts due to its toxicity and high cost. The osmium ] is regenerated by oxidizing agents, such as ], ] (NMO, see ]), and ]. These oxidizing reagents do not react with the alkenes on their own. Other sources of osmium tetroxide include potassium osmate(VI) dihydrate (K<sub>2</sub>OsO<sub>4</sub>·2H<sub>2</sub>O) and osmium(III) chloride hydrate (OsCl<sub>3</sub>·''x''H<sub>2</sub>O) which oxidise to osmium(VIII) in the presence of such oxidants.<ref>{{cite journal|title = On the timing of hydrolysis / reoxidation in the osmium-catalyzed asymmetric dihydroxylation of olefins using potassium ferricyanide as the reoxidant|author = Yasukazu Ogino, Hou Chen, Hoi-Lun Kwong and K. Barry Sharpless|journal = ]|year = 1991|volume = 32|issue = 32|pages = 3965|doi = 10.1016/0040-4039(91)80601-2}}</ref> |
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With ], the ] derivative is produced: |
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===Miscellaneous reactions=== |
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:OsO<sub>4</sub> + Me<sub>3</sub>CNH<sub>2</sub> → OsO<sub>3</sub>(NCMe<sub>3</sub>) + H<sub>2</sub>O |
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OsO<sub>4</sub> does not react with most carbohydrates.<ref name=stain/> It dissolves in alkaline aqueous solution to give the osmate anion OsO<sub>2</sub>(OH)<sub>4</sub><sup>2−</sup>.<ref>Thomas R. Dulski , ASTM International, 1996, ISBN 0803120664 p. 130</ref> OsO<sub>4</sub> is a ], and when the ]s are ]s, the oxides can undergo substitution. Thus with ] one obtains the nitrido-oxide: |
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Similarly, with ] one obtains the ]: |
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:OsO<sub>4</sub> + NH<sub>3</sub> + KOH → K + 2 H<sub>2</sub>O |
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:OsO<sub>4</sub> + NH<sub>3</sub> + KOH → K + 2 H<sub>2</sub>O |
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The <sup>-</sup> anion is isoelectronic and isostructural with OsO<sub>4</sub>. Using primary amine tert-BuNH<sub>2</sub> one obtains the corresponding imido derivative: |
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The <sup>−</sup> anion is isoelectronic and isostructural with OsO<sub>4</sub>. |
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:OsO<sub>4</sub> + 4 Me<sub>3</sub>CNH<sub>2</sub> → Os(NCMe<sub>3</sub>)<sub>4</sub> + 4 H<sub>2</sub>O |
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OsO<sub>4</sub> is very soluble in ] and in solution is readily reduced by molecular hydrogen to osmium metal. The suspended osmium metal can be used to ] ] of a wide variety of organic chemicals containing double or triple bonds. |
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OsO<sub>4</sub> is very soluble in ]. In solution, it is readily reduced by hydrogen to osmium metal. The suspended osmium metal can be used to ] ] a wide variety of organic chemicals containing double or triple bonds. |
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:OsO<sub>4</sub> + 4 H<sub>2</sub> → Os + 4 H<sub>2</sub>O |
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OsO<sub>4</sub> undergoes "reductive carbonylation" with ] in methanol at 400 K and 200 sbar to produce the triangular cluster ]: |
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:OsO<sub>4</sub> + 4 H<sub>2</sub> (g) → Os (s) + 4 H<sub>2</sub>O |
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OsO<sub>4</sub> undergoes "reductive carbonylation" with ] in methanol at 400 K and 200 bar of pressure to produce the triangular cluster Os<sub>3</sub>(CO)<sub>12</sub>: |
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:3 OsO<sub>4</sub> + 24 CO → Os<sub>3</sub>(CO)<sub>12</sub> + 12 CO<sub>2</sub><ref name = "h&s"/> |
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====Oxofluorides==== |
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:3 OsO<sub>4</sub> + 24 CO → Os<sub>3</sub>(CO)<sub>12</sub> + 12 CO<sub>2</sub><ref name = "h&s"/> |
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Osmium forms several oxofluorides, all of which are very sensitive to moisture. |
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Purple ''cis''-OsO<sub>2</sub>F<sub>4</sub> forms at 77 K in an anhydrous ] solution:<ref>{{ cite journal |author1=Christe, K. O. |author2=Dixon, D. A. |author3=Mack, H. G. |author4=Oberhammer, H. |author5=Pagelot, A. |author6=Sanders, J. C. P. |author7=Schrobilgen, G. J. | title = Osmium tetrafluoride dioxide, ''cis''-OsO<sub>2</sub>F<sub>4</sub> | year = 1993 | journal = ] | volume = 115 | issue = 24 | pages = 11279–11284 | doi = 10.1021/ja00077a029 }}</ref> |
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: OsO<sub>4</sub> + 2 KrF<sub>2</sub> → ''cis''-OsO<sub>2</sub>F<sub>4</sub> + 2 Kr + O<sub>2</sub> |
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OsO<sub>4</sub> also reacts with F<sub>2</sub> to form yellow OsO<sub>3</sub>F<sub>2</sub>:<ref name=chem>{{ cite book | author = Cotton, S. A. | title = Chemistry of Precious Metals | publisher = Chapman and Hall | location = London | year = 1997 | isbn = 0-7514-0413-6 }}</ref> |
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In this reaction osmium changes oxidation state by eight units. |
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: 2 OsO<sub>4</sub> + 2 F<sub>2</sub> → 2 OsO<sub>3</sub>F<sub>2</sub> + O<sub>2</sub> |
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OsO<sub>4</sub> reacts with one equivalent of F at 298 K and 2 equivalents at 253 K:<ref name = h&s/> |
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: OsO<sub>4</sub> + F → |
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: OsO<sub>4</sub> + 2 F → <sub>2</sub> |
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==Uses== |
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==Uses== |
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===Organic synthesis=== |
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===Organic synthesis=== |
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In organic synthesis OsO<sub>4</sub> is widely used to oxidise ]s to the vicinal diols, adding two ] groups at the same side (]). See reaction and mechanism above. This reaction has been made both catalytic (]) and asymmetric (]). |
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In organic synthesis OsO<sub>4</sub> is widely used to oxidize ]s to the ] diols, adding two ] groups at the same side (]). See reaction and mechanism above. This reaction has been made both catalytic (]) and asymmetric (]). |
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Osmium tetroxide is also used in catalytic amount in the ] to give vicinal amino-alcohols. |
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Osmium(VIII) oxide is also used in catalytic amounts in the ] to give ] amino-alcohols. |
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In combination with ], OsO<sub>4</sub> is used for the oxidative cleavage of ]s (]) when the periodate serves both to cleave the diol formed by dihydroxylation, and to reoxidize the OsO<sub>3</sub> back to OsO<sub>4</sub>. The net transformation is identical to that produced by ]. Below an example from the total synthesis of Isosteviol.<ref>{{cite journal|author = B. B. Snider, J. Y. Kiselgof and B. M. Foxman|title = Total Syntheses of (±)-Isosteviol and (±)-Beyer-15-ene-3β,19-diol by Manganese(III)-Based Oxidative Quadruple Free-Radical Cyclization|year = 1998|journal = ]|volume = 63|issue = 22|pages = 7945–7952|doi = 10.1021/jo981238x}}</ref> |
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In combination with ], OsO<sub>4</sub> is used for the oxidative cleavage of ]s (]) when the periodate serves both to cleave the diol formed by dihydroxylation, and to reoxidize the OsO<sub>3</sub> back to OsO<sub>4</sub>. The net transformation is identical to that produced by ]. Below an example from the total synthesis of Isosteviol.<ref>{{ cite journal |author1=Snider, B. B. |author2=Kiselgof, J. Y. |author3=Foxman, B. M. | title = Total Syntheses of (±)-Isosteviol and (±)-Beyer-15-ene-3β,19-diol by Manganese(III)-Based Oxidative Quadruple Free-Radical Cyclization | year = 1998 | journal = ] | volume = 63 | issue = 22 | pages = 7945–7952 | doi = 10.1021/jo981238x }}</ref> |
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===Biological staining=== |
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===Biological staining=== |
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OsO<sub>4</sub> is a widely used ] agent used in ] (TEM) to provide contrast to the image.<ref name="Bozzola">{{cite book|isbn = 9780763701925|chapter = Specimen Preparation for Transmission Electron Microscopy|pages = 21–31|url = http://books.google.com/?id=RqSMzR-IXk0C&pg=PA21|last = Bozzola|coauthor = Russell, Lonnie D.| year = 1999|publisher = Jones and Bartlett|location = Sudbury, Mass.|title = Electron microscopy : principles and techniques for biologists|first = John J.}}</ref> As a ] stain, it is also useful in ] (SEM) as an alternative to ]. It embeds a heavy metal directly into cell membranes, creating a high secondary ] emission without the need for coating the membrane with a layer of metal, which can obscure details of the cell membrane. In the staining of the ], osmium tetroxide binds ] head regions, thus creating contrast with the neighbouring ] (cytoplasm). Additionally, osmium tetroxide is also used for fixing biological samples in conjunction with HgCl<sub>2</sub>. Its rapid killing abilities are used to quickly kill specimen like protozoa. OsO<sub>4</sub> stabilizes many proteins by transforming them into gels without destroying structural features. Tissue proteins that are stabilized by OsO<sub>4</sub> are not coagulated by alcohols during dehydration.<ref name=stain>{{cite book| pages = 45–61| url = http://books.google.com/?id=nfsVMH8it1kC| title = Principles and techniques of electron microscopy: biological applications| author = M. A. Hayat |
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OsO<sub>4</sub> is a widely used ] agent used in ] (TEM) to provide contrast to the image.<ref name="Bozzola">{{ cite book |author1=Bozzola, J. J. |author2=Russell, L. D. | chapter = Specimen Preparation for Transmission Electron Microscopy | title = Electron Microscopy: Principles and Techniques for Biologists | year = 1999 | publisher = Jones and Bartlett | location = Sudbury, MA | pages = 21–31 | isbn = 978-0-7637-0192-5 | chapter-url = https://books.google.com/books?id=RqSMzR-IXk0C&pg=PA21 }}</ref> This staining method may also be known in the literature as the OTO<ref>{{Cite journal|last1=Seligman|first1=Arnold M.|last2=Wasserkrug|first2=Hannah L.|last3=Hanker|first3=Jacob S.|title=A new staining method (OTO) for enhancing contrast of lipid--containing membranes and droplets in osmium tetroxide--fixed tissue with osmiophilic thiocarbohydrazide(TCH)|date=1966-08-01|journal=The Journal of Cell Biology|volume=30|issue=2|pages=424–432|doi=10.1083/jcb.30.2.424|issn=0021-9525|pmc=2106998|pmid=4165523}}</ref><ref>{{Citation |last1=Unger |first1=Ann-Katrin |date=2020 |work=Volume Microscopy : Multiscale Imaging with Photons, Electrons, and Ions |pages=165–178 |editor-last=Wacker |editor-first=Irene |place=New York, NY |publisher=Springer US |language=en |doi=10.1007/978-1-0716-0691-9_9 |isbn=978-1-0716-0691-9 |last2=Neujahr |first2=Ralph |last3=Hawes |first3=Chris |last4=Hummel |first4=Eric |title=Improving Serial Block Face SEM by Focal Charge Compensation |series=Neuromethods |volume=155 |s2cid=226563386 |editor2-last=Hummel |editor2-first=Eric |editor3-last=Burgold |editor3-first=Steffen |editor4-last=Schröder |editor4-first=Rasmus}}</ref> (osmium-thiocarbohydrazide-osmium) method, or osmium impregnation<ref>{{Cite journal|last1=Tapia|first1=Juan C.|last2=Kasthuri|first2=Narayanan|last3=Hayworth|first3=Kenneth|last4=Schalek|first4=Richard|last5=Lichtman|first5=Jeff W.|last6=Smith|first6=Stephen J|last7=Buchanan|first7=JoAnn|date=2012-01-12|title=High contrast en bloc staining of neuronal tissue for field emission scanning electron microscopy|journal=Nature Protocols|volume=7|issue=2|pages=193–206|doi=10.1038/nprot.2011.439|issn=1754-2189|pmc=3701260|pmid=22240582}}</ref> technique or simply as osmium staining. As a ] stain, it is also useful in ] (SEM) as an alternative to ]. It embeds a heavy metal directly into cell membranes, creating a high electron scattering rate without the need for coating the membrane with a layer of metal, which can obscure details of the cell membrane. In the staining of the ], osmium(VIII) oxide binds ] head regions, thus creating contrast with the neighbouring ] (cytoplasm). Additionally, osmium(VIII) oxide is also used for fixing biological samples in conjunction with HgCl<sub>2</sub>. Its rapid killing abilities are used to quickly kill live specimens such as protozoa. OsO<sub>4</sub> stabilizes many proteins by transforming them into gels without destroying structural features. Tissue proteins that are stabilized by OsO<sub>4</sub> are not coagulated by alcohols during dehydration.<ref name=stain>{{ cite book | author = Hayat, M. A. | title = Principles and Techniques of Electron Microscopy: Biological Applications | publisher = Cambridge University Press | year = 2000 | pages = 45–61 | isbn = 0-521-63287-0 | url = https://books.google.com/books?id=nfsVMH8it1kC }}</ref> Osmium(VIII) oxide is also used as a stain for lipids in optical microscopy.<ref>{{ cite journal | title = A simple protocol for paraffin-embedded myelin sheath staining with osmium(VIII) oxide for light microscope observation |author1=Di Scipio, F. |author2=Raimondo, S. |author3=Tos, P. |author4=Geuna, S. | journal = Microscopy Research and Technique | year = 2008 | volume = 71 | issue = 7 | pages = 497–502 | doi = 10.1002/jemt.20577 | pmid = 18320578 |s2cid=9404999 }}</ref> OsO<sub>4</sub> also stains the human cornea (see ]). |
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| publisher = Cambridge University Press| year = 2000| isbn = 0521632870}}</ref> Osmium tetroxide is also used as a stain for lipids in optical microscopy.<ref>{{cite journal| title = A simple protocol for paraffin-embedded myelin sheath staining with osmium tetroxide for light microscope observation| author = F. Di Scipio ''et al.''| journal = Microscopy Research and Technique| volume = 71|page = 497| doi = 10.1002/jemt.20577| pmid = 18320578| year = 2008| issue = 7}}</ref> OsO<sub>4</sub> also stains the human cornea (see ]). |
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===Polymer staining=== |
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===Polymer staining=== |
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It is also used to stain ] preferentially, the best known example being block copolymers where one phase can be stained so as to show the ] of the material. For example, styrene-butadiene block copolymers have a central ] chain with polystyrene end caps. When treated with OsO<sub>4</sub>, the butadiene matrix reacts preferentially and so absorbs the oxide. The presence of a heavy metal is sufficient to block the electron beam, so the polystyrene domains are seen clearly in thin films in ]. |
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It is also used to stain ] preferentially, the best known example being block copolymers where one phase can be stained so as to show the ] of the material. For example, styrene-butadiene block copolymers have a central ] chain with polystyrene end caps. When treated with OsO<sub>4</sub>, the butadiene matrix reacts preferentially and so absorbs the oxide. The presence of a heavy metal is sufficient to block the electron beam, so the polystyrene domains are seen clearly in thin films in ]. |
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===Osmeth=== |
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OsO<sub>4</sub> can be recycled and stored in the form of '''osmeth''', a golden crystalline solid. Osmeth is OsO<sub>4</sub> complexed with ] and does not emit toxic fumes as opposed to pure OsO<sub>4</sub>. It can be dissolved in ] (THF) and diluted in an aqueous ] to make a dilute (0.25%) working ] of OsO<sub>4</sub>.<ref>Kiernan, J.A. Department of Anatomy & Cell Biology, The University of Western Ontario. </ref> |
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===Osmium ore refining=== |
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===Osmium ore refining=== |
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OsO<sub>4</sub> is an intermediate in osmium ore refining. Osmium residues are reacted with Na<sub>2</sub>O<sub>2</sub> forming <sup>2−</sup> anions, which, when reacted with ] (Cl<sub>2</sub>) gas and heated, form OsO<sub>4</sub>. The oxide is dissolved in alcoholic ] forming <sup>2−</sup> anions, which, when reacted with ], forms OsO<sub>2</sub>Cl<sub>2</sub>(NH<sub>4</sub>)<sub>4</sub>. This is ignited under ] (H<sub>2</sub>) gas leaving behind pure osmium (Os).<ref name = thomson/> |
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OsO<sub>4</sub> is an intermediate in the extraction of osmium from its ores. Osmium-containing residues are treated with sodium peroxide (Na<sub>2</sub>O<sub>2</sub>) forming Na<sub>2</sub>, which is soluble. When exposed to ], this salt gives OsO<sub>4</sub>. In the final stages of refining, crude OsO<sub>4</sub> is dissolved in alcoholic ] forming Na<sub>2</sub>, which, when treated with ], to give (NH<sub>4</sub>)<sub>4</sub>. This salt is reduced under ] to give osmium.<ref name=thompson/> |
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===Buckminsterfullerene adduct=== |
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===Buckminsterfullerene adduct=== |
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OsO<sub>4</sub> allowed for the confirmation of the soccer ball model of ], a 60 atom ] ]. The ], formed from a derivative of OsO<sub>4</sub>, was C<sub>60</sub>(OsO<sub>4</sub>)(4-''tert''-]])<sub>2</sub>. The adduct broke the fullerene's symmetry allowing for crystallization and confirmation of the structure of C<sub>60</sub> by ].<ref>{{cite journal|author = J. M. Hawkins, A. Meyer, T. A. Lewis, S. Loren and F. J. Hollander|title = Crystal Structure of Osmylated C60: Confirmation of the Soccer Ball Framework|year = 1991|journal = ]|volume = 252|issue = 5003|pages = 312–313|doi = 10.1126/science.252.5003.312|pmid = 17769278}}</ref> |
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OsO<sub>4</sub> allowed for the confirmation of the soccer ball model of ], a 60-atom ] ]. The ], formed from a derivative of OsO<sub>4</sub>, was C<sub>60</sub>(OsO<sub>4</sub>)(4-''tert''-]])<sub>2</sub>. The adduct broke the fullerene's symmetry, allowing for crystallization and confirmation of the structure of C<sub>60</sub> by ].<ref>{{ cite journal |author1=Hawkins, J. M. |author2=Meyer, A. |author3=Lewis, T. A. |author4=Loren, S. |author5=Hollander, F. J. | title = Crystal Structure of Osmylated C<sub>60</sub>: Confirmation of the Soccer Ball Framework | year = 1991 | journal = ] | volume = 252 | issue = 5003 | pages = 312–313 | doi = 10.1126/science.252.5003.312 | pmid = 17769278 |bibcode=1991Sci...252..312H |s2cid=36255748 }}</ref> |
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===Medicine=== |
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The only known clinical use of osmium tetroxide is for the treatment of arthritis.<ref>{{cite journal|last=Sheppeard|first=H.|author2=D. J. Ward|journal=Rheumatology|date=1980|volume=19|pages=25–29|doi=10.1093/rheumatology/19.1.25|pmid=7361025|title=Intra-articular osmic acid in rheumatoid arthritis: five years' experience|issue=1}}</ref> The lack of reports of long-term side effects from the local administration of osmium tetroxide (OsO<sub>4</sub>) suggest that osmium itself can be ], though this depends on the osmium compound administered. |
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==Safety considerations== |
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==Safety considerations== |
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]OsO<sub>4</sub> 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 ], and subsequent death. Noticeable symptoms can take hours to appear after exposure. |
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OsO<sub>4</sub> also stains the human ], which can lead to blindness if proper safety precautions are not observed. The permissible exposure limit for osmium tetroxide (8 hour time-weighted average) is 2 µg/m<sup>3</sup>.<ref name=niosh>{{cite news| url = http://www.cdc.gov/niosh/idlh/20816120.html| accessdate= 2010-10-25| title = Documentation for Immediately Dangerous to Life or Health Concentrations (IDLHs)| publisher = Centers for Disease Control}}</ref> Osmium tetroxide can penetrate plastics and therefore is stored in glass in a cold place.<ref name=stain/> |
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OsO<sub>4</sub> will irreversibly stain the human ], which can lead to blindness. The permissible exposure limit for osmium(VIII) oxide (8 hour time-weighted average) is 2 μg/m<sup>3</sup>.<ref name=niosh>{{ cite web | url = https://www.cdc.gov/niosh/idlh/20816120.html | title = Osmium tetroxide (as Os) | work = Documentation for Immediately Dangerous to Life or Health Concentrations (IDLHs)| date = 2 November 2018 | publisher = Centers for Disease Control }}</ref> Osmium(VIII) oxide can penetrate plastics and food packaging, and therefore must be stored in glass under refrigeration.<ref name=stain/> |
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On April 6, 2004 British intelligence sources believed they had foiled a plot to detonate a bomb involving OsO<sub>4</sub>.<ref>{{cite news|title = Chemical 'bomb plot' in UK foiled|url = http://news.bbc.co.uk/1/hi/uk/3603961.stm|publisher = ]|date = 2004-04-06}}</ref> Experts interviewed by ] affirmed osmium tetroxide's toxicity, though some highlighted the difficulties of using it in a weapon: osmium tetroxide is very expensive. The osmium tetroxide may be destroyed by the blast; what remaining toxic fumes may also be dispersed by the blast as well.<ref>{{cite news|url = http://technology.newscientist.com/article/dn4863-experts-divided-over-poison-bomb-claim.html|publisher = ]|title = Experts divided over poison bomb claim|author = Shaoni Bhattacharya|date = 2004-04-07}}</ref> |
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==References== |
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==References== |
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{{reflist|2}} |
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{{reflist}} |
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==External links== |
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==External links== |
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{{Osmium compounds}} |
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{{Osmium compounds}} |
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{{Oxides}} |
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{{DEFAULTSORT:Osmium Tetroxide}} |
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