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Osmocene - Wikipedia

From Wikipedia, the free encyclopedia

Osmocene
Names

Preferred IUPAC name Osmocene^[1]
Other names Di(cyclopentadienyl)osmium Bis(η⁵-cyclopentadienyl)osmium
Identifiers
CAS Number	1273-81-0^Y
3D model (JSmol)	Interactive image
ChemSpider	71493^N
ECHA InfoCard	100.013.687
PubChem CID	6432038
CompTox Dashboard (EPA)	DTXSID00925840
InChI InChI=1S/2C5H5.Os/c21-2-4-5-3-1;/h21-5H;/q2-1;+2^N Key: RMYKEUKAFJLONI-UHFFFAOYSA-N^N InChI=1/2C5H5.Os/c21-2-4-5-3-1;/h21-5H;/q2-1;+2 Key: RMYKEUKAFJLONI-UHFFFAOYAC
SMILES [cH-]1cccc1.[cH-]1cccc1.[Os+2]
Properties
Chemical formula	C₁₀H₁₀Os
Molar mass	320.42 g·mol⁻¹
Appearance	white solid
Melting point	234 °C
Boiling point	298 °C
Structure^[2]
Crystal structure	orthorhombic
Space group	Pnma, No. 62
Point group	D_5h
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

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

Synthesis

Osmocene is commercially available. It may be prepared by the reaction of osmium tetroxide with hydrobromic acid followed by zinc and cyclopentadiene.^[2]

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.^[3]

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.^[2]

Compared to ferrocene and ruthenocene, osmocene is less reactive towards electrophilic aromatic substitution but has the greatest tendency towards adduct formation with Lewis acids.^[4]

The osmocenium cation [Os(C₅H₅)₂]⁺ dimerizes, forming a binuclear complex with an Os-Os bond.^[5] In contrast, the decamethylosmocenium cation [Os(C₅(CH₃)₅)₂]⁺ is stable as the monomer.^[6]

Uses

In 2009, Horst Kunkely and Arnd Vogler reported the possibility of photocatalytic water splitting with osmocene as a catalyst.^[7]

References

^ International Union of Pure and Applied Chemistry (2014). Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. p. 1041. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
^ ^a ^b ^c 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. S2CID 96874978.
^ 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.
^ Kur, Sally A.; Rheingold, Arnold L.; Winter, Charles H. (1995). "Synthesis, Characterization, and Halogenation of Decakis( acetoxymercurio)osmoene. Crystal and Molecular Structure of Decachloroosmocene". Inorg. Chem. 34 (1): 414–416. doi:10.1021/ic00105a067.
^ Droege, Michael W.; Harman, W. Dean; Taube, Henry (1987). "Higher Oxidation State Chemistry of Osmocene: Dimeric Nature of the Osmocenium Ion". Inorg. Chem. 26 (8): 1309–1315. doi:10.1021/ic00255a023.
^ 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.
^ 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. PMID 19173275.