Vanadocene
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| Names | |
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| IUPAC name
Vanadocene
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| Systematic IUPAC name
Bis(η5-cyclopentadienyl)vanadium | |
| Identifiers | |
3D model (JSmol)
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| ECHA InfoCard | 100.149.756 |
PubChem CID
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| UNII | |
CompTox Dashboard (EPA)
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| 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
[edit]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
[edit]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
[edit]With only 15 valence electrons, vanadocene is highly reactive. For example,it adds alkynes to yield the corresponding vanadium-cyclopropene complexes.[4]
Likewise, high carbon monoxide pressures give CpV(CO)4.[5] 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[6] or ferrocenium in toluene will easily oxidize an electron from the complex:[7]
- 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.[7]
Related compounds
[edit]- (Cycloheptatrienyl)(cyclopentadienyl)vanadium (V(C5H5)(C7H7)
References
[edit]- ^ 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.
- ^ 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.
- ^ Lorber, C. "Vanadium Organometallics." Chapter 5.01. Comprehensive Organometallic Chemistry III. Elsevier, 2007. 1-60.
- ^ Jordan, Markus (2009). Azine in der Koordinationssphäre von Vanadocenderivaten unterschiedlicher Oxidationsstufen (PhD thesis). Universität Oldenburg.
- ^ King, R. B.; Stone, F. G. A. (1963). "Cyclopentadienyl Metal Carbonyls and Some Derivatives". Inorganic Syntheses. 7: 99. doi:10.1002/9780470132388.ch31.
- ^ Birmingham, John M. "Synthesis of cyclopentadienyl metal compounds": 384. doi:10.1016/S0065-3055(08)60082-9.
{{cite journal}}: Cite journal requires|journal=(help) - ^ a b 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.