Vanadium hexacarbonyl

Vanadium hexacarbonyl
Names

IUPAC name hexacarbonylvanadium(0)
Identifiers
CAS Number	20644-87-5^Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:37857^Y
ECHA InfoCard	100.039.928
PubChem CID	519800
UNII	WA8Q7FLK2X^Y
SMILES O=C=[V](=C=O)(=C=O)(=C=O)(=C=O)=C=O
Properties
Chemical formula	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)
Solubility in water	insoluble
Solubility in other solvents	5 g/L hexane; more soluble in dichloromethane
Structure
Crystal structure	orthorhombic
Coordination geometry	octahedral
Dipole moment	0 D
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	CO source
Related compounds
Related compounds	Chromium hexacarbonyl Molybdenum hexacarbonyl Tungsten hexacarbonyl Seaborgium hexacarbonyl Dimanganese decacarbonyl Dirhenium decacarbonyl Iron pentacarbonyl Diiron nonacarbonyl Triruthenium dodecacarbonyl Triosmium dodecacarbonyl Dicobalt octacarbonyl Tetrarhodium dodecacarbonyl Tetrairidium dodecacarbonyl Nickel tetracarbonyl
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is ^YN ?) Infobox references

Chemical compound

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 M_x(CO)_y follow the 18-electron rule, whereas V(CO)₆ has 17 valence electrons.^[1]

Synthesis

According to the original synthesis by Calderazzo, 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

^ Elschenbroich, C.; Salzer, A. (1992). Organometallics: A Concise Introduction (2nd ed.). Weinheim: Wiley-VCH. ISBN 3-527-28165-7.
^ Liu, X.; Ellis, J. E. (2004). "Hexacarbonylvanadate(1−) and Hexacarbonylvanadium(0)". Inorg. Synth. 34: 96–103. doi:10.1002/0471653683.ch3. ISBN 0-471-64750-0.
^ Bellard, S.; Rubinson, K. A.; Sheldrick, G. M. (1979). "Crystal and Molecular Structure of Vanadium Hexacarbonyl". Acta Crystallographica. B35 (2): 271–274. Bibcode:1979AcCrB..35..271B. doi:10.1107/S0567740879003332.