| 词条 | Draft:Vanadocene |
| 释义 |
Vanadocene, bis(η5-cyclopentadienyl)vanadium(II) is the organometallic compound with the formula V(C5H5)2 (commonly abbreviated Cp2V). This violet crystal has 15 valence electrons with only one unpaired electron, making it paramagnetic. Vanadocene has relatively limited practical use, but it has been extensively studied. Like most metallocenes, vanadocene is a stable compound. Structure and bondingV(C5H5)2 is a metallocene, a group 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 at the center of the two cyclopentadienyl rings at a crystallographic center of inversion. The average bond distance of vanadium to carbon is 2.26 Å.[1] The Cp rings of vanadocene are dynamically disordered at temperatures above 170 K and are only fully ordered at 108 K. PreparationVanadocene was first prepared in 1954 by Birmingham, Fischer and Wilkinson via a reduction of vanadocene dichloride in THF 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[ZnCl6] with NaCp.[3] Chemical PropertiesVanadocene is a reactive molecule that can add many reagents. One reaction involves vanadium monoxide, leading to an ionic vanadocene derivative when performed in inert atmosphere.2 Cp2V + V(CO)6 → [Cp2V(CO)2][V(CO)6] Vanadocene is readily oxidized . A good example of this would be it being oxidized to the monocation when treated with a ferrocenium salt in toluene.[4] VCp2 +[FeCp2]BR4 → [VCp2]BR4 + FeCp2 Where R = Ph or 4-C6H4F These monocation compounds are extremely air sensitive and have a redox potential of -1.10 V.[4] {{Chembox| ImageFile = | ImageSize = | ImageAlt = | IUPACName = Bis(cyclopentadienyl)vanadium | OtherNames = Vanadocene | Section1 = {{Chembox Identifiers | CASNo = 1277-47-0 | PubChem = | SMILES = }} | Section2 = {{Chembox Properties | Formula = V(C5H5)2 | MolarMass = 181.128 g/mol | Appearance = Violet Crystal | Density = | MeltingPt = 167 ˚C | BoilingPt = | Solubility = }} | Section3 = {{Chembox Hazards | MainHazards = | FlashPt = | Autoignition = }} }} References1. ^Rogers, Robin D., Jerry L. Atwood, Don Foust, and Marvin D. Rausch. "Crystal Stucture of Vanadocene." Journal of Crystal and Molecular Structure 11 (1981): 183-88. doi: 10.1007/BF01210393 2. ^Birmingham, J. M., A. K. Fischer, and G. Wilkinson. "The Reduction of Bis-cyclopentadienyl Compounds." Die Naturwissenschaften 42.4 (1955): 96. doi:10.1007/BF00617242 3. ^Lorber, C. "Vanadium Organometallics." Chapter 5.01. Comprehensive Organometallic Chemistry III. Elsevier, 2007. 1-60. 4. ^1 Calderazzo, Fausto, Isabella Ferri, Guido Pampaloni, and Ulli Englert. "Oxidation Products of Vanadocene and of Its Permethylated Analogue, Including the Isolation and the Reactivity of the Unsolvated [VCp]Cation." Organometallics 18.13 (1999): 2452-458. doi: 10.1021/om9809320 |
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