Vanadocene
Encyclopedia
Vanadocene, bisvanadium, is the organometallic compound 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.
, 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
. The vanadium(II) center resides equidistant between the center of the two cyclopentadienyl
rings at a crystallographic center of inversion. The average V-C bond distance is 2.26 Å. The Cp rings of vanadocene are dynamically disordered at temperatures above 170 K and are only fully ordered at 108 K.
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 [V2Cl3(THF)6]2[ZnCl6] with cyclopentadienylsodium.
Vanadocene is readily oxidized to the monocation when treated with a ferrocenium salt in toluene.
These monocations are extremely air-sensitive and have a redox potential of -1.10 V.
Structure and bonding
V(C5H5)2 is a metalloceneMetallocene
A metallocene is a compound typically consisting of two cyclopentadienyl anions bound to a metal center in the oxidation state II, with the resulting general formula 2M. Closely related to the metallocenes are the metallocene derivatives, e.g. titanocene dichloride, vanadocene dichloride...
, 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 group
The symmetry group of an object is the group of all isometries under which it is invariant with composition as the operation...
. The vanadium(II) center resides equidistant between the center of the two cyclopentadienyl
Cyclopentadienyl
In organic chemistry, cyclopentadienyl is a cyclic group of atoms with the formula C5H5. Cyclopentadienyl are closely related to cyclopentadiene. Cyclopentadienyl have five carbon atoms bonded together in a pentagonal planar ring, all five of which are bonded to individual hydrogen atoms...
rings at a crystallographic center of inversion. The average V-C bond distance is 2.26 Å. 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 WilkinsonGeoffrey Wilkinson
Sir Geoffrey Wilkinson FRS was a Nobel laureate English chemist who pioneered inorganic chemistry and homogeneous transition metal catalysis.-Biography:...
via a reduction of vanadocene dichloride
Vanadocene dichloride
Vanadocene dichloride, dichloro bisvanadium is 2VCl2 . It is a structural analoque of titanocene dichloride but with vanadium instead of titanium....
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 [V2Cl3(THF)6]2[ZnCl6] with cyclopentadienylsodium.
- 2 [V2Cl3(THF)6]2[ZnCl6] + 8 NaCp + THF → 4 Cp2V
Properties
Vanadocene is a reactive molecule. One reaction involves carbon monoxide, leading to an ionic vanadocene derivative when performed in inert atmosphere:- Cp2V + V(CO)6 → [Cp2V(CO)2][V(CO)6]
Vanadocene is readily oxidized to the monocation when treated with a ferrocenium salt in toluene.
- VCp2 + [FeCp2]BR4 → [VCp2]BR4 + FeCp2 (R = Ph or 4-C6H4F)
These monocations are extremely air-sensitive and have a redox potential of -1.10 V.