Vanadocene
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| IUPAC name
Vanadocene
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| Systematic IUPAC name
Bis(η5-cyclopentadienyl)vanadium | |
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3D model (JSmol)
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PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| V(C5H5)2 | |
| Molar mass | 181.128 g/mol |
| Appearance | Violet crystals |
| Melting point | 167 °C (333 °F; 440 K) |
| Hazards | |
| GHS labelling:[1] | |
| 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
[edit | edit source]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 | edit source]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 | edit source]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 | edit source]- (Cycloheptatrienyl)(cyclopentadienyl)vanadium (V(C5H5)(C7H7)
References
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- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ Lorber, C. "Vanadium Organometallics." Chapter 5.01. Comprehensive Organometallic Chemistry III. Elsevier, 2007. 1-60.
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