Vanadium hexacarbonyl

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Vanadium hexacarbonyl
Vanadium hexacarbonyl
Names
IUPAC name
hexacarbonylvanadium(0)
Identifiers
3D model (
JSmol
)
ChEBI
ECHA InfoCard
 100.039.928 Edit this at Wikidata
UNII
  • O=C=[V](=C=O)(=C=O)(=C=O)(=C=O)=C=O
Properties
C6O6V
Molar mass 219.00 g/mol
Appearance blue-green crystals
yellow solutions
Density 1.7 g/cm3
Melting point decomposes
Boiling point sublimes at 50 °C (122 °F; 323 K) (15 mmHg)
insoluble
Solubility in other solvents 5 g/L hexane;
more soluble in dichloromethane
Structure
orthorhombic
octahedral
0 D
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 CO source
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Vanadium hexacarbonyl is the inorganic compound with the formula V(CO)6. It is a blue-black volatile solid. This highly reactive species is noteworthy from theoretical perspectives as a rare isolable homoleptic metal carbonyl that is paramagnetic. Most species with the formula Mx(CO)y follow the 18-electron rule, whereas V(CO)6 has 17 valence electrons.[1]

Synthesis

Traditionally V(CO)6 is prepared in two-steps via the intermediacy of V(CO)−
6. In the first step, VCl3 is reduced with metallic sodium under 200 atm CO at 160 °C. The solvent for this reduction is typically diglyme, CH3OCH2CH2OCH2CH2OCH3. This triether solubilizes sodium salts, akin to the behavior of a crown ether:

4 Na + VCl3 + 6 CO + 2 diglyme → [Na(diglyme)2][V(CO)6] + 3 NaCl

The resulting anion is oxidized with acid:[2]

2 V(CO)−
6 + 2 H3PO4 → 2 V(CO)6 + H2 + 2 H
2PO−
4

Reactions

Vanadium hexacarbonyl is thermally unstable. Its primary reaction is reduction to the monoanion V(CO)−
6, salts of which are well studied. It is also susceptible to substitution by tertiary

phosphine ligands, often leading to disproportionation
.

V(CO)6 reacts with sources of the cyclopentadienyl anion to give the orange four-legged piano stool complex (C5H5)V(CO)4 (m.p. 136 °C). Like many charge-neutral organometallic compounds, this half-sandwich species is volatile. In the original preparation of this species, C5H5HgCl was employed as the source of C
5H−
5.

Structure

V(CO)6 adopts an

octahedral coordination geometry and is isostructural with chromium hexacarbonyl, even though they have differing valence electron counts. High resolution X-ray crystallography indicates that the molecule is slightly distorted with two (axial) shorter V–C distances of 1.993(2) Å vs. four (equatorial) 2.005(2) Å. Even though V(−I) is a larger ion than V(0), the V–C distances in V(CO)−
6 are 0.07 Å shorter than in the neutral precursor.[3]

References

  1. ISBN 3-527-28165-7
    .
  2. ISBN 0-471-64750-0
    .
  3. doi:10.1107/S0567740879003332
    .

Further reading
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