Osmium oxide pentafluoride

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Osmium oxide pentafluoride
Names
Other names
Osmium oxypentafluoride
Identifiers
3D model (JSmol)
  • InChI=1S/5FH.O.Os/h5*1H;;/q;;;;;;+5/p-5
    Key: KMJGCQQKIWSRQV-UHFFFAOYSA-I
  • F[Os](F)(F)(F)(F)=O
Properties [1]
OsOF5
Molar mass 301.22 g·mol−1
Appearanceemerald green solid
Melting point 59.2 °C (138.6 °F; 332.3 K)
Boiling point 100.6 °C (213.1 °F; 373.8 K)
Vapor pressure 41.1 mmHg (304.8 K)
917×10−6 cm3/mol (293.8 K)
Structure [2]
Orthorhombic
Pnma
a = 9.540 Å, b = 8.669 Å, c = 5.019 Å
415.1 Å3
4 units per cell
Thermochemistry [1]
Enthalpy of fusion (ΔfH⦵fus)
1.62 kcal/mol
8.75 kcal/mol
10.37 kcal/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Osmium oxide pentafluoride is an inorganic compound with the chemical formula OsOF5. It is a paramagnetic [3] emerald green solid, notable for being a heptavalent osmium compound stable in molecular form under normal temperature and pressure. [1]

Contents

Structure

It is dimorphic, forming orthorhombic crystals and transitioning to a cubic disordered phase at 32.5 °C. [2] OsOF5, in its high temperature form, is indistinguishable crystallographically from OsF6. [2]

Preparation

Osmium oxide pentafluoride can be prepared in several ways.

From elements

It can be prepared by heating osmium metal in a stream of oxygen and fluorine (1:2 v/v). The reaction is self-sustaining after initiation by heat. The resulting product mixture is captured in a cold trap and the osmium hexafluoride byproduct is separated by difference in volatility. The yield is reported to be 50%. [1]

Fluorination of osmium dioxide

Anhydrous osmium dioxide is reacted with a slight excess of fluorine in a closed monel can. The product is separated from the osmium hexafluoride byproduct using the aforementioned technique with a yield of over 90%. [1]

OsO2 + 2.5 F2 → OsOF5 + 0.5 O2

Other fluorinating agents

OsO2 is fluorinated to OsOF5 by ClF3 with quantitative yields at ambient temperature. [4]

OsO4 is fluorinated into a mixture of OsO3F2 and OsOF5 by ClF3 at ambient temperature. [4] The formation of OsOF5 corresponds to a reduction of osmium from +8 to +7. [4]

Other oxide fluorides of osmium are known including: OsO3F2, OsO2F3, and OsOF4. [5] There is some evidence for the existence of OsO2F2. [5]

References

  1. 1 2 3 4 5 Bartlett, Neil; Jha, N. K. (1968-01-01). "The preparation and some physical properties of osmium oxide pentafluoride, OsOF5". Journal of the Chemical Society A: Inorganic, Physical, Theoretical: 536–543. doi:10.1039/J19680000536. ISSN   0022-4944.
  2. 1 2 3 Bartlett, Neil; Trotter, James (1968-01-01). "The structure of the orthorhombic phase of osmium oxide pentafluoride, OsOF5". Journal of the Chemical Society A: Inorganic, Physical, Theoretical: 543–547. doi:10.1039/J19680000543. ISSN   0022-4944.
  3. ↑ Holloway, John H.; Hope, Eric G.; Raynor, J. Barrie; Townson, Paul T. (1992-01-01). "Magnetic resonance studies on osmium pentafluoride oxide". Journal of the Chemical Society, Dalton Transactions (7): 1131–1134. doi:10.1039/DT9920001131. ISSN   1364-5447.
  4. 1 2 3 Bougon, R.; Cicha, W. V.; Isabey, J. (1994-06-01). "Low-temperature fluorination of ruthenium and osmium di- and tetra-oxides". Journal of Fluorine Chemistry. 67 (3): 271–276. Bibcode:1994JFluC..67..271B. doi:10.1016/0022-1139(93)02972-H. ISSN   0022-1139.
  5. 1 2 Hope, Eric G.; Levason, William; Ogden, J. Steven (1988-01-01). "Spectroscopic studies on matrix isolated osmium pentafluoride oxide, osmium tetrafluoride oxide, and osmium difluoride trioxide". Journal of the Chemical Society, Dalton Transactions (1): 61–65. doi:10.1039/DT9880000061. ISSN   1364-5447.
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