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Vanadocene, bis(η5-cyclopentadienyl) vanadium, is the
Likewise, high carbon monoxide pressures give CpV(CO)4.
That piano-stool complex can rearrange to an ionic, mixed-valence, vanadium hexacarbonyl derivative:
:Cp2V + V(CO)6 → p2V(CO)2sup>+ (CO)6sup>−
Vanadocene is extremely air-sensitive, and either 12% (by mass)
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 ...
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 ametallocene
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 that typically have a metal ion sandwiched between two cyclopentadienyl rings. In the solid state, the molecule has D5d symmetry
Symmetry () in everyday life refers to a sense of harmonious and beautiful proportion and balance. In mathematics, the term has a more precise definition and is usually used to refer to an object that is Invariant (mathematics), invariant und ...
. 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
{{Chemistry index ...
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 via a reduction of vanadocene dichloride 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 Cp2VProperties
With only 15valence electron
In chemistry and physics, valence electrons are electrons in the outermost shell of an atom, and that can participate in the formation of a chemical bond if the outermost shell is not closed. In a single covalent bond, a shared pair forms with b ...
s, vanadocene is highly reactive. For example,it adds alkyne
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Acetylene
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Propyne
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1-Butyne
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...
s to yield the corresponding vanadium-cyclopropene complexes.
:
Likewise, high carbon monoxide pressures give CpV(CO)4.
That piano-stool complex can rearrange to an ionic, mixed-valence, vanadium hexacarbonyl derivative:
:Cp2V + V(CO)6 → p2V(CO)2sup>+ (CO)6sup>−
Vanadocene is extremely air-sensitive, and either 12% (by mass) hydrochloric acid
Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...
or ferrocenium in toluene will easily oxidize an electron from the complex:
:VCp2 + eCp2R4 → Cp2R4 + FeCp2 (R = Ph or 4-C6H4F)
The monocations themselves oxidize in air, having a redox potential of -1.10 V.
Related compounds
* (Cycloheptatrienyl)(cyclopentadienyl)vanadium (References
{{Cyclopentadienide complexes Metallocenes Organovanadium compounds Cyclopentadienyl complexes