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Ruthenocene Eclipsed Conformer Structural Formula.svg
IUPAC names
Other names
ruthenium cyclopentadienyl, cp2Ru
3D model (JSmol)
ECHA InfoCard 100.013.696
Molar mass 231.26 g/mol
Appearance pale yellow powder
Density 1.86 g/cm3 (25 °C)
Melting point 195 to 200 °C (383 to 392 °F; 468 to 473 K)
Boiling point 278 °C (532 °F; 551 K)
Insoluble in water, soluble in most organic solvents
Irritant Xi
R-phrases (outdated) R36/37/38
S-phrases (outdated) S26, S28, S37/39, S45
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Related compounds
Related compounds
cobaltocene, nickelocene, chromocene, ferrocene, osmocene, bis(benzene)chromium
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Ruthenocene is an organoruthenium compound with the formula (C5H5)2Ru. This pale yellow, volatile solid is classified as a sandwich compound and more specifically, as a metallocene.

Structure and bonding[edit]

Ruthenocene consists of a ruthenium ion sandwiched in between two cyclopentadienyl rings. It features ruthenium centre bound symmetrically to the planes of two cyclopentadienyl rings. It is closely related to the isoelectronic ferrocene.

In contrast to ferrocene, wherein the cyclopentadienyl rings are in a staggered conformation, those of ruthenocene crystallise with an eclipsed conformation. This difference is due to the larger ionic radius of ruthenium, which increases the distance between the cyclopentadienyl rings, decreasing steric interactions and allowing an eclipsed conformation to prevail. In solution, these rings rotate with a very low barrier.


Ruthenocene was first synthesized in 1952 by Geoffrey Wilkinson, a Nobel laureate who had collaborated in assigning the structure of ferrocene only a year earlier.[1] Originally, ruthenocene was prepared by the reaction of ruthenium trisacetylacetonate with excess of cyclopentadienylmagnesium bromide.[1]

Ru(acac)3 + 3 C5H5MgBr → Ru(C5H5)2 + 3 "acacMgBr" + "C5H5"

Ruthenocene may also be prepared by the reaction of sodium cyclopentadienide with "ruthenium dichloride" (prepared from ruthenium metal and ruthenium trichloride in situ).[2]

Chemical properties[edit]

Ruthenocene typically oxidises via two electron change, instead of one.[3] With weakly coordinating anions as electrolyte, the oxidation proceeds via a 1e step.[4]

Ruthenocene has been investigated as a photoinitiator for polymerization reactions.[5]


  1. ^ a b Wilkinson, G. (1952). "The Preparation and Some Properties of Ruthenocene and Ruthenicinium Salts". J. Am. Chem. Soc. 74 (23): 6146. doi:10.1021/ja01143a538. .
  2. ^ Bublitz, D. E; McEwen, W. E.; Kleinberg, J. (1973). "Ruthenocene". Organic Syntheses.  ; Collective Volume, 5, p. 1001 
  3. ^ Smith, T. P; Taube, H.; Bino, A.; Cohen, S. (1984). "Reactivity of Haloruthenocene(IV) complexes". Inorg. Chem. 23 (13): 1943. doi:10.1021/ic00181a030. 
  4. ^ Geiger, W. E. and Barrière, F., "Organometallic Electrochemistry Based on Electrolytes Containing Weakly-Coordinating Fluoroarylborate Anions", Accounts of Chemical Research, 2010. doi:10.1021/ar1000023.
  5. ^ Cynthia T. Sanderson, Bentley J. Palmer, Alan Morgan, Michael Murphy, Richard A. Dluhy, Todd Mize, I. Jonathan Amster, and Charles Kutal "Classical Metallocenes as Photoinitiators for the Anionic Polymerization of an Alkyl 2-Cyanoacrylate" Macromolecules 2002, volume 35, pp. 9648-9652.doi:10.1021/ma0212238