Dicobalt octacarbonyl

[4] Each molecule consists of two cobalt atoms bound to eight carbon monoxide ligands, although multiple structural isomers are known.

Acidification produces cobalt tetracarbonyl hydride, HCo(CO)4, which degrades near room temperature to dicobalt octacarbonyl and hydrogen.

[3][7] It can also be prepared by heating cobalt metal to above 250 °C in a stream of carbon monoxide gas at about 200 to 300 atm:[3] It exist as a mixture of rapidly interconverting isomers.

[7] Halogens and related reagents cleave the Co–Co bond to give pentacoordinated halotetracarbonyls: Cobalt tricarbonyl nitrosyl is produced by treatment of dicobalt octacarbonyl with nitric oxide: The Nicholas reaction is a substitution reaction whereby an alkoxy group located on the α-carbon of an alkyne is replaced by another nucleophile.

In the asymmetric synthesis of the Lycopodium alkaloid huperzine-Q, Takayama and co-workers used an intramolecular Pauson–Khand reaction to cyclise an enyne containing a tert-butyldiphenylsilyl (TBDPS) protected primary alcohol.

[17] The preparation of the cyclic siloxane moiety immediately prior to the introduction of the dicobalt octacarbonyl ensures that the product is formed with the desired conformation.

[26] The National Institute for Occupational Safety and Health has recommended that workers should not be exposed to concentrations greater than 0.1 mg/m3 over an eight-hour time-weighted average, without the proper respiratory gear.

Dicobalt octacarbonyl, bridged C2v isomer
Dicobalt octacarbonyl, bridged C2v isomer
NFPA 704 four-colored diamond Health 4: Very short exposure could cause death or major residual injury. E.g. VX gas Flammability 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasoline Instability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calcium Special hazards (white): no code
The Nicholas reaction
The Nicholas reaction
Symmetric diphenylacetylene cyclotrimerization using dicobalt octacarbonyl
Symmetric diphenylacetylene cyclotrimerization using dicobalt octacarbonyl
Asymmetric diphenylacetylene cyclotrimerization using dicobalt octacarbonyl
Asymmetric diphenylacetylene cyclotrimerization using dicobalt octacarbonyl
Catalytic cycle for the hydroformylation of a terminal alkene ( RCH=CH 2 ) to an aldehyde ( RCH 2 CH 2 CHO ): [ 4 ]
  1. Carbon monoxide dissociates from cobalt tetracarbonyl hydride to form the active catalyst, HCo(CO) 3
  2. The cobalt centre π bonds to the alkene
  3. The alkene ligand inserts into the cobalt–hydride bond
  4. An additional carbonyl ligand coordinates
  5. A carbonyl ligand migrates into the cobalt–alkyl bond [ 21 ]
  6. Dihydrogen adds to the acyl complex
  7. The dihidrydo complex eliminates the aldehyde product, [ 22 ] regenerating the catalyst
  8. An unproductive and reversible side reaction
Methylidynetricobaltnonacarbonyl , HCCo 3 (CO) 9 , an organocobalt cluster compound structurally related to tetracobalt dodecacarbonyl