Vanadocene

Vanadocene
Names
IUPAC name
Vanadocene
Systematic IUPAC name
Bis(η5-cyclopentadienyl)vanadium
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.149.756 Edit this at Wikidata
EC Number
  • 620-850-1
UNII
  • InChI=1S/2C5H5.V/c2*1-2-4-5-3-1;/h2*1-5H;/q2*-1;+2
    Key: YXQWGVLNDXNSJJ-UHFFFAOYSA-N
  • c1ccc[cH-]1.c2ccc[cH-]2.[V+2]
Properties
V(C5H5)2
Molar mass 181.128 g/mol
Appearance Violet crystals
Melting point 167 °C (333 °F; 440 K)
Hazards
GHS labelling:
GHS02: FlammableGHS06: Toxic
Danger
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. 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 [V2Cl3(THF)6]2[Zn2Cl6] with cyclopentadienylsodium.

2 [V2Cl3(THF)6]2[Zn2Cl6] + 8 NaCp + THF → 4 Cp2V

Properties

With only 15 valence electrons, vanadocene is highly reactive. For example, it adds alkynes 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:[citation needed]

Cp2V + V(CO)6 → [Cp2V(CO)2]+[V(CO)6]−

Vanadocene is extremely air-sensitive, and either 12% (by mass) hydrochloric acid or ferrocenium in toluene will easily oxidize an electron from the complex:

VCp2 + [FeCp2]BR4 → [VCp2]BR4 + FeCp2 (R = Ph or 4-C6H4F)

The monocations themselves oxidize in air, having a redox potential of -1.10 V.

Halocarbons oxidize vanadocene to the corresponding monohalide, e.g.:

VCp2 + MeI → VCp2I + Me2

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; G. Wilkinson (1955). "The Reduction of Bis-cyclopentadienyl Compounds". Naturwissenschaften. 42 (4): 96. Bibcode:1955NW.....42Q..96B. doi:10.1007/BF00617242. S2CID 44523847.
  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. ↑ King, R. B.; Stone, F. G. A. (1963). "Cyclopentadienyl Metal Carbonyls and Some Derivatives". Inorganic Syntheses. Vol. 7. p. 99. doi:10.1002/9780470132388.ch31.
  6. ↑ Birmingham, John M. (1965). Synthesis of cyclopentadienyl metal compounds. Advances in Organometallic Chemistry. Vol. 2. p. 384. doi:10.1016/S0065-3055(08)60082-9. ISBN 978-0-12-031102-6.
  7. 1 2 Calderazzo, Fausto; Isabella Ferri; Guido Pampaloni; 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.
  8. ↑ de Liefde Meijer, H. J.; Janssen, M. J.; van der Kerk, G. J. M. "Studies in transition metal chemistry, part II: The addition of organic halides to bis-cyclopentadienyl vanadium(II)". Recueil des Travaux Chimiques des Pays-Bas. 80 (8): 831–845. doi:10.1002/recl.19610800805.