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Organovanadium chemistry

From Wikipedia, the free encyclopedia

Organovanadium chemistry is the chemistry of organometallic compounds containing a carbon (C) 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

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Carbonyls

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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

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(Cycloheptatrienyl)(cyclopentadienyl)vanadium is one of many organovanadium compounds that is paramagnetic.

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 (Cp2V):

VCp2Cl2 + LiAlH4 → VCp2
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

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

VCl4 + Al + 2 C6H6 → [V(η6-C6H6)2]AlCl4
[V(η6-C6H6)2]AlCl4 + H2O → V(η6-C6H6)2 + ...

Alkyl and aryl derivatives

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A handful of alkyl and aryl complexes exist. The reactive species V(mesityl)3 forms from VCl3:[7]

VCl3(THF)3 + 3 LiC6H2-2,4,6-Me3 → V(C6H2-2,4,6-Me3)3(THF) + 3 LiCl

This species binds CO and, under appropriate conditions, N2. V(mesityl)3 adds a fourth mesityl group and the resulting "ate complex" can be oxidized to the vanadium(IV) derivative:

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 organovanadium(IV) and organovanadium(V) compounds:

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

Catalysts and reagents

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Well-defined vanadium compounds do not appear as catalysts in any commercial process.[8] 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.[9][10]

References

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  1. ^ Synthesis of Organometallic Compounds: A Practical Guide Sanshiro Komiya Ed. 1997
  2. ^ Kotohiro Nomura; Shu Zhang (2011). "Design of Vanadium Complex Catalysts for Precise Olefin Polymerization". Chem. Rev. 111 (3): 2342–2362. doi:10.1021/cr100207h. PMID 21033737.
  3. ^ Wilkinson, G.; Birmingham, J. G. (1954). "Bis-cyclopentadienyl Compounds of Ti, Zr, V, Nb and Ta". Journal of the American Chemical Society. 76 (17): 4281–4284. doi:10.1021/ja01646a008.
  4. ^ Fischer, Ernst Otto; Schneider, Robert J. J. (1970). "Über Aromatenkomplexe von Metallen, CXIV. Darstellung und Reaktionen von Dicyclopentadienyl-divanadin-pentacarbonyl, (C 5 H 5 ) 2 V 2 (CO) 5". Chemische Berichte. 103 (11): 3684–3695. doi:10.1002/cber.19701031133.
  5. ^ Robert Choukroun, Christian Lorber (2005). "Adventures in Vanadocene Chemistry". Eur. J. Inorg. Chem. 2005 (23): 4683–4692. doi:10.1002/ejic.200500371.
  6. ^ King, R.B.; Stone, F.G.A (1963). "Cyclopentadienyl Metal Carbonyls and Some Derivatives". Inorganic Syntheses. Vol. 7. pp. 99–115. doi:10.1002/9780470132388.ch31. ISBN 978-0-470-13238-8. {{cite book}}: |journal= ignored (help)
  7. ^ Vivanco, M.; Ruiz, J.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. "Chemistry of the vanadium-carbon .sigma. bond. 1. Insertion of carbon monoxide, isocyanides, carbon dioxide, and heterocumulenes into the V-C bond of Tris(mesityl)vanadium(III)" Organometallics 1993 volume 12, 1794–1801. doi:10.1021/om00029a042
  8. ^ Toshikazu Hirao (1997). "Vanadium in Modern Organic Synthesis". Chemical Reviews. 97 (8): 2707–2724. doi:10.1021/cr960014g. PMID 11851478.
  9. ^ Kotohiro Nomura; Shu Zhang (2011). "Design of Vanadium Complex Catalysts for Precise Olefin Polymerization". Chem. Rev. 111 (3): 2342–2362. doi:10.1021/cr100207h. PMID 21033737.
  10. ^ Werner Obrecht; Jean-Pierre Lambert; Michael Happ; Christiane Oppenheimer-Stix; John Dunn; Ralf Krüger (2012). "Rubber, 4. Emulsion Rubber". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.o23_o01. ISBN 978-3527306732.
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