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二茂钒

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二茂钒
IUPAC名
Bis(cyclopentadienyl)vanadium
别名 Vanadocene
识别
CAS号 1277-47-0  ✓
PubChem 18667909
SMILES
性质
化学式 V(C5H5)2
摩尔质量 181.128 g/mol g·mol⁻¹
外观 紫色晶体
熔点 166 °C(439 K)[1]
若非注明,所有数据均出自一般条件(25 ℃,100 kPa)下。

二茂钒,又称双(η5-环戊二烯)钒,是一种有机金属化合物,化学式为V(C5H5)2,一般简称为 Cp2V。它是紫色的顺磁性晶体。二茂钒的实际应用相对有限,但是已经进行了广泛的研究。

结构和成键

V(C5H5)2茂金属的一种,为夹心化合物,金属离子位于两个茂环中间。在固态,这个分子有 D5d对称性,V-C 键的平均键长为 226 pm。[2] 二茂钒的茂环在高于170 K的温度下会动态无序,只有在108 K时才完全有序。

制备

二茂钒首次在1954年由Birmingham、Fischer和Wilkinson合成,他们先用氢化铝二氯化二茂钒还原,再在真空中于100 ˚C升华得到。[3]现在一般通过[V2Cl3(THF)6]2[Zn2Cl6]和环戊二烯钠的加热反应来得到更高产量的二茂钒。[4]

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

性质

二茂钒的化学性质活泼。在惰性气氛中,它和六羰基钒反应,生成离子型二茂钒的衍生物:

Cp2V + V(CO)6 → [Cp2V(CO)2][V(CO)6]

当在甲苯中用二茂铁𬭩盐处理时,二茂钒容易被氧化成单阳离子:[5]

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

这种单阳离子的还原电位为-1.10 V,对空气非常敏感。[5]

参考资料

  1. ^ De Liefde Meijer, H. J.; Van der Kerk, G. J. M. Studies in transition metal chemistry. IV. The suitability of cyclopentadienylvanadium compounds as components of Ziegler-​type polymerization catalysts. Recueil des Travaux Chimiques des Pays-Bas, 1966. 85 (9-10). 1007-1017.
  2. ^ Robin D. Rogers; Jerry L. Atwood; Don Foust & Marvin D. Rausch. Crystal Structure of Vanadocene. Journal of Crystal and Molecular Structure. 1981, 11 (5–6): 183–188. doi:10.1007/BF01210393. 
  3. ^ Birmingham, J. M., A. K. Fischer, and G. Wilkinson. The Reduction of Bis-cyclopentadienyl Compounds. Naturwissenschaften. 1955, 42 (4): 96. doi:10.1007/BF00617242. 
  4. ^ Lorber, C. "Vanadium Organometallics." Chapter 5.01. Comprehensive Organometallic Chemistry III. Elsevier, 2007. 1-60.
  5. ^ 5.0 5.1 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. 1999, 18 (13): 2452–2458. doi:10.1021/om9809320. 
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二茂钒
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