Decamethylcobaltocene is an
organocobalt compound with the formula Co(C
5(CH
3)
5)
2, abbreviated CoCp{{su, p=∗, b=2. It is a dark brown solid. This compound is used as a strong reducing agent in
organometallic chemistry
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
.
Synthesis
Decamethylcobaltocene is prepared by treatment of LiCp* with CoCl
2:
:2 LiCp* + CoCl
2 → 2 LiCl + CoCp*
2
The permethylated form is more air-sensitive than the parent
cobaltocene, owing to the inductive effects of methyl groups. It is a thermally stable compound and undergoes vacuum
sublimation
Sublimation or sublimate may refer to:
* ''Sublimation'' (album), by Canvas Solaris, 2004
* Sublimation (phase transition), directly from the solid to the gas phase
* Sublimation (psychology), a mature type of defense mechanism
* Sublimate of mer ...
.
Bonding
Co(C
5Me
5)
2 is a
metallocene, having idealized D
5d symmetry. Like cobaltocene, decamethylcobaltocene has a 19 electron count in its valence shell and is paramagnetic.
It is used as a one-electron
reducing agent. Relative to the
ferrocene
Ferrocene is an organometallic compound with the formula . The molecule is a complex consisting of two cyclopentadienyl rings bound to a central iron atom. It is an orange solid with a camphor-like odor, that sublimes above room temperature, a ...
/
ferrocenium couple, the redox potential for the
oCp*2sup>+/0 couple is -1.94 V compared to the
oCp2sup>+/0 couple of -1.33 V (in
dichloromethane
Dichloromethane (DCM or methylene chloride, methylene bichloride) is an organochlorine compound with the formula . This colorless, volatile liquid with a chloroform-like, sweet odour is widely used as a solvent. Although it is not miscible with ...
). For comparison, the difference between the redox ferrocene and its permethylated derivative FeCp*
2+/0 couple is -0.59 V (also in dichloromethane).
Structure
Decamethylcobaltocene and
decamethylferrocene
Decamethylferrocene or bis(pentamethylcyclopentadienyl)iron(II) is a chemical compound with formula or . It is a sandwich compound, whose molecule has an iron(II) cation attached by coordination bonds between two pentamethylcyclopentadienyl ani ...
have very similar structures. The additional electron occupies an orbital that is anti-bonding with respect to the Co-C bonds. Co-C distances of 2.118 Å at room temperature are slightly longer than seen in other metallocenes such as the Fe-C bonds in ferrocene, and fairly longer than its parent cobaltocene at 2.096 Å at room temperature (in the gas-phase, the Co-C distances in Cp
2Co is 2.119 Å, closely resembling the Co-C bond lengths of decamethylcobaltocene.
[Antipin, Yu M., Augart, N., Boese, R., Schmid, G. Redetermination of the cobaltocene crystal structure at 100K and 297K. Structural Chemistry. Volume 4, No. 2. 1993. P. 91-101.]
An illustrative redox reaction of decamethylcobaltocene is:
:2 CoCp*
2 + C
60 → 2
oCp*2sup>+ +
60sup>2−
References
Organocobalt compounds
Metallocenes
Pentamethylcyclopentadienyl complexes
One-electron reducing agents