Organovanadium chemistry

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Organovanadium chemistry is the chemistry of organometallic compounds containing a carbon to vanadium (V) chemical bond.[1] Organovanadium compounds find only minor use as reagents in organic synthesis but are significant for polymer chemistry as catalysts.[2]

Oxidation states for vanadium are +2, +3, +4 and +5. Low valency vanadium is usually stabilized with carbonyl ligands. Oxo derivatives are relatively common, unlike the organic complexes of neighboring elements.

Compound classes

Carbonyls

Vanadium carbonyl can be prepared by reductive carbonylation of vanadium salts:

4 Na + VCl3 + 6 CO → Na[V(CO)6] + 3 NaCl

The salt can be oxidized to the 17e binary carbonyl V(CO)6.

Cyclopentadienyl derivatives

Vanadocene dichloride, the first organovanadium complexes to be reported,[3] is prepared from sodium cyclopentadienyl and vanadium tetrachloride:

2 NaC5H5 + VCl4 → VCp2Cl2 + 2NaCl

Reduction of this compound gives the parent vanadocene (Cp)2V:

VCp2Cl2 + LiAlH4 → V(Cp)2
Cp2V2(CO)5 featuring a pair of semi-bridging CO ligands.[4]

Vanadocene is the lightest transition metal metallocene that is isolable at room temperature.[5] Vanadocene reacts with high pressures of carbon monoxide to give CpV(CO)4.[6] Photolysis of the tetracarbonyl gives Cp2V2(CO)5. Several analogous indenyl complexes are known.

Monocyclopentadienyl vanadium chlorides include CpVCl3 and the diamagnetic CpVOCl2.

Arene complexes

Vanadium forms a variety of arene complexes, e.g. with benzene:

VCl4 + AlCl3 + C6H6 → [V(η6C6H6)2][AlH4]
[V(η6C6H6)2][AlH4] + H2O → V(η6C6H6)2

Alkyl and aryl derivatives

A handful of alkyl and aryl complexes exist for example with mesitylene groups:

VCl3(THF)3 + (mes)MgBr → V(mes)3(THF)
V(mes)3(THF) + LiMes → Li[V(mes)4]
Li[V(mes)4] + air → V(mes)4(THF)

The tetrakis(norbornyl) complex is also known.

Vanadium oxytrichloride is a starting material for vanadium(V) compounds:

VOCl3 + Li(mes) → Li[VO(mes)3]
Li[VO(mes)3] + chloranil → VO(mes)3
VOCl3 + ZnPh2 → VOPhCl2

Catalysts and reagents

Well-defined vanadium compounds do not appear as catalysts in any commercial process.[7] However organovanadium species are clearly implicated as catalysts for the production of butadiene-based rubbers. These catalysts are generated in situ by treating soluble coordination complexes such as vanadium(III) acetylacetonate with organoaluminium activators.[8] [9]

References

  1. ^ Synthesis of Organometallic Compounds: A Practical Guide Sanshiro Komiya Ed. 1997
  2. ^ "Design of Vanadium Complex Catalysts for Precise Olefin Polymerization". Chem. Rev. 111: 2342–2362. 2011. doi:10.1021/cr100207h. {{cite journal}}: Cite uses deprecated parameter |authors= (help)
  3. ^ Wilkinson, G.; Birmingham, J. G. (1954). "Bis-cyclopentadienyl Compounds of Ti, Zr, V, Nb and Ta". J. Am. Chem. Soc. 76 (17): 4281–4284. doi:10.1021/ja01646a008.
  4. ^ "A Donor Semibridge? Molecular Structures of Dicyclopentadienyldivanadiumtetracarbonyltriphenylphosphine and Dicyclopentadienyldivanadiumpentacarbonyl". Inorganic Chemistry. 19: 2755–2762. 1980. doi:10.1021/ic50211a052. {{cite journal}}: Cite uses deprecated parameter |authors= (help)
  5. ^ Robert Choukroun, Christian Lorber (2005). "Adventures in Vanadocene Chemistry". Eur. J. Inorg. Chem.: 4683–4692. doi:10.1002/ejic.200500371.
  6. ^ King, R.B.; Stone, F.G.A (1963). "Cyclopentadienyl Metal Carbonyls and Some Derivatives". Inorg. Synth. 7: 99. doi:10.1002/9780470132388.ch31.
  7. ^ Toshikazu Hirao (1997). "Vanadium in Modern Organic Synthesis". Chemical Reviews. 97: 2707. doi:10.1021/cr960014g.
  8. ^ "Design of Vanadium Complex Catalysts for Precise Olefin Polymerization". Chem. Rev. 111: 2342–2362. 2011. doi:10.1021/cr100207h. {{cite journal}}: Cite uses deprecated parameter |authors= (help)
  9. ^ "Rubber, 4. Emulsion Rubber". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. 2012. doi:10.1002/14356007.o23_o01. ISBN 978-3527306732.
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