Vanadocene, bis(η⁵-cyclopentadienyl) vanadium, is the

organometallic compound Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...

with the formula V(C₅H₅)₂, commonly abbreviated Cp₂V. It is a violet crystalline, paramagnetic solid. Vanadocene has relatively limited practical use, but it has been extensively studied.

Structure and bonding

V(C₅H₅)₂ is a

metallocene A metallocene is a compound typically consisting of two cyclopentadienyl anions (, abbreviated Cp) bound to a metallic element, metal center (M) in the oxidation state II, with the resulting general formula Closely related to the metallocenes are ...

, a class of

organometallic compounds Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...

that typically have a metal ion sandwiched between two cyclopentadienyl rings. In the solid state, the molecule has D_5d

symmetry Symmetry (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definit ...

. The vanadium(II) center resides equidistant between the center of the two

cyclopentadienyl Cyclopentadienyl can refer to *Cyclopentadienyl anion, or cyclopentadienide, **Cyclopentadienyl ligand *Cyclopentadienyl radical, • *Cyclopentadienyl cation, See also *Pentadienyl In organic chemistry, pentadienyl refers to the organic radic ...

rings at a crystallographic center of inversion. The average V-C bond distance is 226 pm. The Cp rings of vanadocene are dynamically disordered at temperatures above 170 K and are only fully ordered at 108 K.

Preparation

Vanadocene was first prepared in 1954 by Birmingham, Fischer, and

Wilkinson Wilkinson may refer to: People * Wilkinson (surname), a surname (including a list of people with the name) Places in the United States * Wilkinson, Illinois * Wilkinson, Indiana, a town in Hancock County * Wilkinson, Minnesota * Wilkinson, Mis ...

via a reduction of

vanadocene dichloride Vanadocene dichloride is an organometallic complex with formula ( ''η''5- C5H5)2VCl2 (commonly abbreviated as Cp2VCl2). It is a structural analogue of titanocene dichloride but with vanadium(IV) instead of titanium(IV). This compound has one unpa ...

with aluminum hydride, after which vanadocene was sublimed in vacuum at 100 ˚C. A modern synthesis of vanadocene that allows production in higher quantities requires treating ₂Cl₃(THF)₆sub>2 n₂Cl₆with cyclopentadienylsodium. : 2 ₂Cl₃(THF)₆sub>2 n₂Cl₆ + 8 NaCp + THF → 4 Cp₂V

Properties

Vanadocene is a reactive molecule. As it only has 15 valence electrons available, it readily reacts with many ligands. With alkynes, for example, it reacts to yield the corresponding vanadium-cyclopropene complexes. : Vanadocene_ethin_reaction

One reaction involves carbon monoxide, leading to an ionic vanadocene derivative when performed in inert atmosphere: :Cp₂V + V(CO)₆ → p₂V(CO)₂V(CO)₆] Vanadocene is readily oxidized to the monocation when treated with a

ferrocenium Ferrocenium tetrafluoroborate is an organometallic compound with the formula e(C5H5)2F4. This salt is composed of the cation e(C5H5)2sup>+ and the tetrafluoroborate anion (). The related hexafluorophosphate is also a popular reagent with simil ...

salt in toluene. :VCp₂ + eCp₂R₄ → Cp₂R₄ + FeCp₂ (R = Ph or 4-C₆H₄F) These monocations are extremely

air-sensitive Air sensitivity is a term used, particularly in chemistry, to denote the reactivity of chemical compounds with some constituent of air. Most often, reactions occur with atmospheric oxygen (O2) or water vapor (H2O), although reactions with the other ...

and have a redox potential of -1.10 V. Vanadocene reacts with high pressures of carbon monoxide to give CpV(CO)₄.

References

{{Reflist Metallocenes Organovanadium compounds Cyclopentadienyl complexes