Vanadocene


Vanadocene, bis vanadium, is the organometallic compound with the formula V2, 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

V2 is a metallocene, 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 center resides equidistant between the center of the two cyclopentadienyl 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 2 with cyclopentadienylsodium.

Properties

Vanadocene is a reactive molecule. One reaction involves carbon monoxide, leading to an ionic vanadocene derivative when performed in inert atmosphere:
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.
Vanadocene reacts with high pressures of carbon monoxide to give CpV4.