Organovanadium chemistry
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
[edit]Carbonyls
[edit]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
[edit]![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Trovacene.svg/130px-Trovacene.svg.png)
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
![](http://upload.wikimedia.org/wikipedia/commons/thumb/7/74/CPPCDV01.png/220px-CPPCDV01.png)
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
[edit]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
[edit]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
[edit]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
[edit]- ^ Synthesis of Organometallic Compounds: A Practical Guide Sanshiro Komiya Ed. 1997
- ^ 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.
- ^ 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.
- ^ 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.
- ^ Robert Choukroun, Christian Lorber (2005). "Adventures in Vanadocene Chemistry". Eur. J. Inorg. Chem. 2005 (23): 4683–4692. doi:10.1002/ejic.200500371.
- ^ 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}}
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ignored (help) - ^ 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
- ^ Toshikazu Hirao (1997). "Vanadium in Modern Organic Synthesis". Chemical Reviews. 97 (8): 2707–2724. doi:10.1021/cr960014g. PMID 11851478.
- ^ 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.
- ^ 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.