Osmocene

Osmocene is an organoosmium compound found as a white solid. It is a metallocene with the formula Os(C5H5)2.

Osmocene
Names
IUPAC name
osmocene, bis(η5-cyclopentadienyl)osmium
Other names
di(cyclopentadienyl)osmium
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.013.687
Properties
C10H10Os
Molar mass 320.42 g·mol−1
Appearance white solid
Melting point 234 °C
Boiling point 298 °C
Structure[1]
orthorhombic
Pnma, No. 62
D5h
Related compounds
Related compounds
 ferrocene, ruthenocene
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Synthesis

Osmocene is commercially available. It may be prepared by the reaction of osmium tetroxide with hydrobromic acid followed by zinc and cyclopentadiene.[1]

It was first synthesized by Ernst Otto Fischer and Heinrich Grumbert via the reaction of osmium(IV) chloride with excess sodium cyclopentadienide in dimethoxyethane, where osmium(II) chloride is presumed to be an intermediate formed in situ. Alternatively, cyclopentadienyl magnesium bromide could be reacted with osmium(IV) chloride, though this has worse yields.[2]

Properties

Osmocene is a white solid. The molecular structure features an osmium ion sandwiched between two cyclopentadienyl rings. It is isomorphous to the lighter homologue ruthenocene, both crystallizing in an eclipsed conformation. This is in contrast to ferrocene, which crystallizes with its rings staggered.[1]

Compared to ferrocene and ruthenocene, osmocene is less reactive towards electrophilic aromatic substitution but has the greatest tendency towards adduct formation with Lewis acids.[3]

The osmocenium cation [Os(C5H5)2]+ dimerizes, forming a binuclear complex with an Os-Os bond.[4] In contrast, the decamethylosmocenium cation [Os(C5(CH3)5)2]+ is stable as the monomer.[5]

Uses

In 2009, Horst Kunkely and Arnd Vogler reported the possibility of photocatalytic water splitting with osmocene as a catalyst.[6]

References
  1. Bobyens, J. C. A.; Levendis, D. C.; Bruce, Michael I.; Williams, Michael L. (1986). "Crystal structure of osmocene, Os(η-C5H5)2". Journal of Crystallographic and Spectroscopic Research. 16 (4): 519. doi:10.1007/BF01161040.
  2. Fischer, Ernst Otto; Grumbert, Heinrich (1959). "Über Aromatenkomplexe von Metallen, XXIX. Di-cyclopentadienyl-osmium". Chem. Ber. 92 (9): 2302–2309. doi:10.1002/cber.19590920948.
  3. Kur, Sally A.; Rheingold, Arnold L.; Winter, Charles H. "Synthesis, Characterization, and Halogenation of Decakis( acetoxymercurio)osmoene. Crystal and Molecular Structure of Decachloroosmocene". Inorg. Chem. 34 (1): 414-416. doi:10.1021/ic00105a067.
  4. Droege, Michael W.; Harman, W. Dean; Taube, Henry. "Higher Oxidation State Chemistry of Osmocene: Dimeric Nature of the Osmocenium Ion". Inorg. Chem. 26 (8): 1309–1315. doi:10.1021/ic00255a023.
  5. Astruc, Didier (2007). "Metallocenes and Sandwich Complexes". Organometallic Chemistry and Catalysis. Springer-Verlag. p. 263. doi:10.1007/978-3-540-46129-6_13. ISBN 978-3-540-46128-9.
  6. Kunkely, Horst; Vogler, Arnd (2009). "Water Splitting by Light with Osmocene as Photocatalyst". Angew. Chem. Int. Ed. 48 (9): 1685–1687. doi:10.1002/anie.200804712.
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