Vanadium carbonyl
Encyclopedia
Vanadium carbonyl, also known as vanadium hexacarbonyl, is the inorganic compound
with the formula
V(CO)6. This highly reactive species is noteworthy from theoretical and scholarly perspectives. It is a rare isolable homoleptic
metal carbonyl
that is paramagnetic. Most species with the formula Mx(CO)y follow the 18e rule, whereas V(CO)6 has 17 valence electrons.
− . 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
:
The resulting anion is oxidized with acid:
An improved low pressure synthesis has been developed.
ligands, often leading to disproportionation
.
V(CO)6 reacts with sources of the cyclopentadienyl
anion to give the orange-coloured 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 C5H5.
.
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
V(CO)6. This highly reactive species is noteworthy from theoretical and scholarly perspectives. It is a rare isolable homoleptic
Homoleptic
In inorganic chemistry, a homoleptic chemical compound is a metal compound with all ligands identical. The term uses a homo prefix to indicate that something is the same for all....
metal carbonyl
Metal carbonyl
Metal carbonyls are coordination complexes of transition metals with carbon monoxide ligands. These complexes may be homoleptic, that is containing only CO ligands, such as nickel carbonyl , but more commonly metal carbonyls contain a mix of ligands, such as Re3Cl...
that is paramagnetic. Most species with the formula Mx(CO)y follow the 18e rule, whereas V(CO)6 has 17 valence electrons.
Synthesis
Traditionally V(CO)6 is prepared in two-steps via the intermediacy of [V(CO)6]Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
under 200 atm CO at 160 °C. The solvent for this reduction is typically diglyme
Diglyme
Diglyme, or bis ether, is a solvent with a high boiling point. It is an organic compound which is the dimethyl ether of diethylene glycol. It is a clear, colorless liquid with a slight ether-like odor...
, CH3OCH2CH2OCH2CH2OCH3. This triether
Ether
Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...
solubilizes sodium salts, akin to the behavior of a crown ether
Crown ether
Crown ethers are cyclic chemical compounds that consist of a ring containing several ether groups. The most common crown ethers are oligomers of ethylene oxide, the repeating unit being ethyleneoxy, i.e., -CH2CH2O-. Important members of this series are the tetramer , the pentamer , and the hexamer...
:
- 4 Na + VCl3 + 6 CO + 2 diglyme → [Na(diglyme)2][V(CO)6] + 3 NaCl
The resulting anion is oxidized with acid:
- 2 [V(CO)6]- + H3PO4 → 2 V(CO)6 + H2 + 2 H2PO4-
An improved low pressure synthesis has been developed.
Reactions
The most characteristic reaction for V(CO)6 is a thermally sensitive material. 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 phosphinePhosphine
Phosphine is the compound with the chemical formula PH3. It is a colorless, flammable, toxic gas. Pure phosphine is odourless, but technical grade samples have a highly unpleasant odor like garlic or rotting fish, due to the presence of substituted phosphine and diphosphine...
ligands, often leading to disproportionation
Disproportionation
Disproportionation, also known as dismutation is used to describe a specific type of redox reaction in which a species is simultaneously reduced and oxidized so as to form two different products....
.
V(CO)6 reacts with sources of the cyclopentadienyl
Cyclopentadienyl
In organic chemistry, cyclopentadienyl is a cyclic group of atoms with the formula C5H5. Cyclopentadienyl are closely related to cyclopentadiene. Cyclopentadienyl have five carbon atoms bonded together in a pentagonal planar ring, all five of which are bonded to individual hydrogen atoms...
anion to give the orange-coloured 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 C5H5.
Structure
V(CO)6 adopts an octahedral coordination geometry. High resolution X-ray crystallography indicates that the molecule is slightly distorted with two (trans) shorter V-C distances of 1.993 (2) vs. four (equatorial) 2.005 (2) Å. Such a distortion could be due to a Jahn-Teller effectJahn-Teller effect
The Jahn–Teller effect, sometimes also known as Jahn–Teller distortion, or the Jahn–Teller theorem, describes the geometrical distortion of non-linear molecules under certain situations. This electronic effect is named after Hermann Arthur Jahn and Edward Teller, who proved, using group theory,...
.
Further reading
- Original synthesis: Calderazzo, F.; Ercoli, R., "Synthesis of V(CO)6 and Hexacarbonyl Vanadates" Chimica e l'Industria 1962, volume 44, 990-6.