Ruthenocene

Ruthenocene, C₁₀H₁₀Ru, is an organometallic compound consisting of a ruthenium ion sandwiched in between two cyclopentadiene rings. This structure can be classified as a sandwich compound and more specifically, as a metallocene.

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History

Ruthenocene was first synthesized in 1952 by Geoffery Wilkinson, a nobel prize laureate for his contribution for the discovery of ferrocene a year earlier. ^[1]

Structure

This metallocene has ruthenium(II) bound symmetrically between the planes of two cyclopentadienyl rings with the π-electrons of which are involved in filling the 3d orbitals of the ruthenium. ^[1]Ferrocene, the first metallocene discovered as well as the first metallocene with its x-ray crystal structure solved, is analogous to ruthenocene.

Chemical Properties

Ruthenocene is analogous to ferrocene and undergoes many of the same reactions such as oxidation with bromine water and aqueous silver sulfate. However, there are some small differences between the two. Ruthenocene, when oxidized electrochemically, produces a two electron change instead of one. ^[2] Additionally, ruthenocene is different from some other metallocenes such as nickelocene due to its electron count. Nickelocene has an electron count of 20 while ruthenocene has 18 electrons. This allows for a "more stable" compound when the 18 electron rule is invoked.

Preparation

Originally, ruthenocene was prepared by the reaction of ruthenium(III) acetylacetonate with a fivefold excess of cyclopentadienylmagnesium bromide. ^[1]

Ruthenocene may also be prepared by the following synthesis ^[3]

Uses

Several of the uses for ruthenocene exploit its ability to transfer electrons and therefore is a good photoinitiator for polymerization reactions. ^[4]

Additionally, ruthenocene forms a complex with halogens, Ru(cp)₂X⁺ in which the metal is in the oxidation state 4+. This allows for the exploration of chemistry with metals of such high oxidation state. ^[2]

References

1. ^ ^{a b c} Wilkinson, G. (1952). "The Preparation and Some Properties of Ruthenocene and Ruthenicinium Salts" J. Am. Chem. Soc. 74: 6146.
2. ^ ^{a b} Smith, T. P; Taube, H.; Bino, A.; Cohen, S. (1984). "Reactivity of Haloruthenocene(IV) complexes" Inorg. Chem. 23: 1943.
3. ^ Bublitz, D. E; McEwen, W. E.; Kleinberg, J. (1973). "Ruthenocene" Organic Syntheses 5: 1001.
4. ^ Sanderson, C., et al. (2002). "Classical Metallocenes as Photoinitiators for the Anionic Polymerization of an Alkyl 2-Cyanoacrylate" Macromolecules 35: 9648.