Vanadium, hexacarbonyl

The O oxidation state is known in vanadium hexacarbonyl. V(CO)(,. a blue-green, sublimable solid. In the molecule VfCO), if each CO molecule is assumed to donate two electrons to the vanadium atom, the latter is still one electron short of the next noble gas configuration (krypton) the compound is therefore paramagnetic, and is easily reduced to form [VfCO, )]. giving it the... 

Mono- and diphenylphosphine also give the corresponding dimeric complexes with vanadium hexacarbonyl. 

The doubly charged Mn(II) cation is paramagnetic and isoelectronic with vanadium hexacarbonyl and neutral chromium pentacarbonyl iodide. These are examples of some of the few carbonyl compounds which contravene the rare gas formalism (/, 57). 

Vanadium hexacarbonyl readily reverts to its anionic form, thereby filling all of its bonding orbitals, and is consequently a useful, albeit expensive, one-electron oxidizing agent. 

The known vanadium carbonyl cations are of two types, namely a tetracarbonyl, [AreneV(CO)4]+, and a dicarbonyl, [Cp2V(CO)2]+. The tetracarbonyl derivatives are readily prepared under mild conditions by the reaction of an arene with vanadium hexacarbonyl. The arenes used include benzene, its methyl derivatives 28, 29), naphthalene, and anisole 29). The cation is probably formed by oxidation of the intermediary arene vanadium tricarbonyl. 

No carbonyl cations of vanadium with a-donor ligands have been reported. When Lewis bases react with vanadium hexacarbonyl, either a substituted derivative or a hexacarbonylvanadate salt is obtained. The latter is formed by disproportionation, which also produces a carbonyl-free cation. 

J. C. Bernier, and O. Kahn, Magnetic Behaviour of Vanadium Hexacarbonyl, Chem. Phys. Lett. 19, 414-417 (1973). 

Vanadium hexacarbonyl reacts with various arenes yielding complexes [(arene)V(CO)4]" [V(CO)6] from which hexafluorphosphate or tetra-phenylborate salts can be prepared by metathesis reaction (50, 52). The cation [(CeHe)V(CO)4] reacts with NaBH4 to give the neutral cyclo-hexadienyl compound (CeH7)V(CO)4 (51). Similar results are observed with methyl-substituted derivatives. The addition of the hydride ion was shown to occur preferentially at unsubstituted positions of the aromatic ring. 

Use Source of vanadium hexacarbonyl by treatment with phosphoric acid under special conditions. 

Vanadium, hexaaqua-electron transfer, 367, 369 Vanadium, hexacarbonyl-exchange reactions, 288... 

Vanadium hexacarbonyl is a pyrophoric compound. It can explode on heating. 

Cycloheptatriene reacts with vanadium hexacarbonyl to afford in 21% yield a dark green, diamagnetic 7r-tropylium-vanadium tricarbonyl [7t-C7H7V(CO)3] which is isoelectronic with [7r-C7H7Cr(CO)3]+ (132). Infrared and NMR spectra suggest, and an X-ray study (6) confirms, the presence of the tropylium cation symmetrically bound to the metal. The stability order (indicated qualitatively by sensitivity to air in solid state and in solution) in the isoelectronic series of aromatic metal tricarbonyls is 7r-C7H7V- (CO) < ir-C H.Cr (CO)s < Tr-CsHsMnHCO),... 

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