Cobalt carbonyl hydride

Structural formula
General
Surname	Cobalt carbonyl hydride
other names	Tetracarbonylhydridocobalt Cobalt carbonyl hydrogen Cobalt tetracarbonyl hydride Cobalt hydrocarbonyl
Molecular formula	[CoH (CO) 4 ]
Brief description	yellowish liquid
External identifiers / databases
CAS number 16842-03-8 PubChem 61848 Wikidata Q410517
properties
Molar mass	171.98 g mol −1
Physical state	liquid
Melting point	−26.2 ° C
boiling point	Decomposition from −18 ° C
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 .

Cobalt carbonyl hydride is a chemical compound of cobalt and is one of the carbonyl complexes . In addition to carbonyl ligands, a hydrogen atom is also bound to the cobalt atom. It is a yellowish, air-sensitive, easily decomposing liquid .

Extraction and presentation

Cobalt carbonyl hydride can be prepared from dicobalt octacarbonyl . For this purpose, dicobalt octacarbonyl is reacted with sodium , whereby the cobalt-cobalt bond is broken and sodium tetracarbonylcobaltate is formed. Reaction with an acid produces cobalt carbonyl hydride.

Technically, cobalt carbonyl hydride is produced by reductive carbonylation of cobalt oxides with carbon monoxide and hydrogen. At first, dicobalt octacarbonyl is formed, which is split by the hydrogen.

properties

The cobalt carbonyl hydride complex has a trigonal-bipyramidal structure. The hydrogen atom and a carbonyl ligand are arranged axially , the three other carbonyl ligands equatorially. The cobalt-hydrogen distance is 114 pm, the cobalt-carbon distance 176 pm for the axial CO ligands and 182 pm for the equatorial CO ligands.

The hydrogen ligand is acidic and can easily be split off. The pKa value of the complex is 8.3, measured in acetonitrile . In water, the compound with a pKa value of 1 is a strong acid.

use

Cobalt carbonyl hydride is used industrially in hydroformylation . The complex serves as a catalyst for the production of aldehydes from alkenes . It enables the insertion of carbon monoxide into a C – H bond of the alkene.

Hydroformylation catalytic cycle

The synthesis using cobalt catalysts has, however, often been replaced by rhodium catalysts, as these allow milder reaction conditions and a more selective reaction.

Individual evidence

1. ↑ Entry on Hydrido…. In: Römpp Online . Georg Thieme Verlag, accessed on December 13, 2015.
2. ↑ ^{a b c} Entry on cobalt carbonyl hydrogen in the GESTIS substance database of the IFA , accessed on February 28, 2017(JavaScript required) .
3. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
4. ↑ Christoph Elschenbroich: Organometallchemie. 6th edition, Teubner Wiesbaden, 2008, ISBN 978-3-8351-0167-8 , p. 349.
5. ↑ ^{a b c} Christoph Elschenbroich: Organometallchemie. 6th edition, Teubner Wiesbaden, 2008, ISBN 978-3-8351-0167-8 , pp. 633-637.
6. ^ EA McNeill, FR Scholer: Molecular structure of the gaseous metal carbonyl hydrides of manganese, iron, and cobalt. In: Journal of the American Chemical Society. 99, 1977, pp. 6243-6249, doi : 10.1021 / ja00461a011 .
7. ↑ Eric J. Moore, Jeffrey M. Sullivan, Jack R. Norton: Kinetic and thermodynamic acidity of hydrido transition-metal complexes. 3. Thermodynamic acidity of common mononuclear carbonyl hydrides. In: Journal of the American Chemical Society. 108, 1986, pp. 2257-2263, doi : 10.1021 / ja00269a022 .
8. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 .