Vanadium hexacarbonyl

Structural formula
General
Surname	Vanadium hexacarbonyl
other names	Vanadium carbonyl
Molecular formula	V (CO) 6
Brief description	bluish green crystals
External identifiers / databases
CAS number 20644-87-5 EC number 243-937-2 ECHA InfoCard 100,039,928 PubChem 519800 Wikidata Q419078
properties
Molar mass	219.0 g mol −1
Physical state	firmly
Melting point	Decomposition from 70 ° C
solubility	almost insoluble in water and ethanol slightly soluble in hexane soluble in other organic solvents
safety instructions
GHS hazard labeling no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Vanadium hexarbonyl is a metal carbonyl with the chemical formula V (CO) ₆ . This highly reactive species is remarkable from a theoretical and scientific perspective. It is a rare example of an isolable homoleptic metal carbonyl that is paramagnetic . Most metal carbonyls with the formula Me _x (CO) _y follow the 18-electron rule , while V (CO) _{6 has} only 17 valence electrons .

synthesis

Traditionally, V (CO) _{6 is produced} in two steps via the intermediate H [V (CO) ₆ ]. In a first step, VCl ₃ is reduced with metallic sodium under 200 atm CO at 160 ° C. The solvent for this reduction is usually diglyme , CH ₃ OCH ₂ CH ₂ OCH ₂ CH ₂ OCH ₃ . This triether dissolves sodium salts in a similar way to a crown ether :

${\displaystyle \mathrm {VCl_{3}\ +\ 4\ Na\ +\ 6\ CO\ +\ Diglyme\ {\xrightarrow {(200\ bar,\ 433\ K,\ 48\ h)}}} }$ ${\displaystyle \mathrm {\ Na(digly)_{2}[V(CO)_{6}]\ +\ 3\ NaCl} }$

${\displaystyle \mathrm {[V(CO)_{6}]^{-}\ +\ H^{+}\ {\xrightarrow {\ }}H[V(CO)_{6}]\ {\xrightarrow {\ }}V(CO)_{6}\ +\ H_{2}} }$

In the meantime, Ellis and Liu have developed an improved low-pressure synthesis.

properties

Physical Properties

Vanadium hexacarbonyl is a solid, crystalline substance with a bluish-green color at room temperature. It does not dissolve in water or ethanol, little in saturated hydrocarbons such as hexane, but well in other organic solvents and the solution turns yellow. The wave number of the CO stretching vibration ν _{CO of} the free carbon monoxide is 1976 cm ⁻¹ .

V (CO) ₆ has an octahedral coordination geometry (O _h ). High resolution X-ray crystallography shows that the molecule is slightly distorted with two shorter V – C bonds of 199.3 pm and four equatorial ones of 200.5 pm. Such a distortion could be due to the Jahn-Teller effect .

Chemical properties

V (CO) ₆ reacts with cyclopentadienyl anions to form an orange complex (C ₅ H ₅ ) V (CO) ₄ (m.p. 136 ° C). Like many charge-neutral organometallic compounds, this half-sandwich complex is highly volatile.

V (CO) ₆ is a thermally sensitive material. Its primary reaction is the reduction to the monoanion [V (CO) ₆ ] ^- as well as the substitution by phosphanes , often with disproportionation . Vanadium hexacarbonyl can release toxic compounds such as carbon monoxide and vanadium oxides upon decomposition . The substance is a pyrophoric compound that can explode when heated.

use

Vanadium hexacarbonyl is used as a catalyst in isomerization and hydrogenation reactions .

Individual evidence

1. ↑ ^{a b c d e f g h i} Pradyot Patnaik: A Comprehensive Guide to the Hazardous Properties of Chemical Substances. 3rd edition, John Wiley and Sons, 2007, ISBN 978-0-470-13494-8 , p. 628.
2. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
3. ↑ ^{a b c} Christoph Elschenbroich : Organometallchemie , 6th edition, Teubner, Wiesbaden 2008, ISBN 978-3-8351-0167-8 , p. 330.
4. ^ X. Liu, JE Ellis: Hexacarbonylvanadate (1−) and Hexacarbonylvanadium (0). In: Inorganic Syntheses , 2004 , Volume 34, ISBN 0-471-64750-0 , pp. 96-103 ( limited preview in Google book search).
5. ↑ S. Bellard, KA Rubinson, GM Sheldrick: Crystal and molecular structure of vanadium hexacarbonyl. In: Acta Crystallographica , 1979 , Volume B35, pp. 271-274; doi : 10.1107 / S0567740879003332 .

literature

• F. Calderazzo, R. Ercoli: Synthesis of V (CO) ₆ and Hexacarbonylvanadaten. In: Chimica e l'Industria. 1962, Volume 44, pp. 990-996.