Vanadocene

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Vanadocene
Names
IUPAC name
Bis(cyclopentadienyl)vanadium
Other names
Vanadocene
Identifiers
3D model (JSmol)
ECHA InfoCard 100.149.756 Edit this at Wikidata
UNII
  • c1ccc[cH-]1.c2ccc[cH-]2.[V+2]
Properties
V(C5H5)2
Molar mass 181.128 g/mol
Appearance Violet Crystal
Melting point 167 °C (333 °F; 440 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Vanadocene, bis(η5-cyclopentadienyl) vanadium, 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.

Structure and bonding

V(C5H5)2 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(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 226 pm.[1] 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.[2] A modern synthesis of vanadocene that allows production in higher quantities requires treating [V2Cl3(THF)6]2[Zn2Cl6] with cyclopentadienylsodium.[3]

2 [V2Cl3(THF)6]2[Zn2Cl6] + 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.[4]

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.[5]

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.[5]

Vanadocene reacts with high pressures of carbon monoxide to give CpV(CO)4.[6]

References

  1. ^ Robin D. Rogers; Jerry L. Atwood; Don Foust & Marvin D. Rausch (1981). "Crystal Structure of Vanadocene". Journal of Crystal and Molecular Structure. 11 (5–6): 183–188. doi:10.1007/BF01210393. S2CID 93048446.
  2. ^ Birmingham, J. M., A. K. Fischer, and G. Wilkinson (1955). "The Reduction of Bis-cyclopentadienyl Compounds". Naturwissenschaften. 42 (4): 96. Bibcode:1955NW.....42Q..96B. doi:10.1007/BF00617242. S2CID 44523847.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. ^ Lorber, C. "Vanadium Organometallics." Chapter 5.01. Comprehensive Organometallic Chemistry III. Elsevier, 2007. 1-60.
  4. ^ Jordan, Markus (2009). Azine in der Koordinationssphäre von Vanadocenderivaten unterschiedlicher Oxidationsstufen (PhD thesis). Universität Oldenburg.
  5. ^ a b Calderazzo, Fausto, Isabella Ferri, Guido Pampaloni, and Ulli Englert (1999). "Oxidation Products of Vanadocene and of Its Permethylated Analogue, Including the Isolation and the Reactivity of the Unsolvated [VCp]Cation". Organometallics. 18 (13): 2452–2458. doi:10.1021/om9809320.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  6. ^ King, R.B.; Stone, F.G.A. (1963). "Cyclopentadienyl Metal Carbonyls and Some Derivatives". Inorganic Syntheses. Vol. 7. pp. 99–115. doi:10.1002/9780470132388.ch31. ISBN 9780470132388. {{cite book}}: |journal= ignored (help)
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