Cobaltocene

Cobaltocene is the organometallic compound with the formula Co(C5H5)2, a metallocene in which cobalt is sandwiched between two η5-cyclopentadienyl rings. It is the cobalt analog of ferrocene and is commonly referred to as bis(cyclopentadienyl)cobalt.

The neutral complex is paramagnetic and contains an unpaired electron, giving it a 19-electron count in the typical electron-counting scheme for metallocenes. This odd-electron configuration makes cobaltocene a one-electron reducing agent in chemical reactions, in contrast to the closed-shell ferrocene.

Synthesis of cobaltocene typically involves the reduction of the cobaltocenium cation, [Co(C5H5)2]+, using strong reductants such as alkali metals or related reagents. The corresponding salts, including Na[Co(C5H5)2], are well known and serve as stable sources of cobaltocene or its radical anion under appropriate conditions.

Properties and handling of cobaltocene include its sensitivity to air and moisture, requiring handling under inert atmosphere. It is soluble in nonpolar organic solvents such as toluene and hexane. The compound can be oxidized to the cobaltocenium cation, [Co(C5H5)2]+, which is diamagnetic and 18-electron.

Applications of cobaltocene center on its role as a strong one-electron donor in organic and organometallic synthesis, as a model system for electron-transfer studies, and in related areas of molecular electronics and redox chemistry. Its chemistry is often discussed in relation to ferrocene and other metallocenes.

See also: ferrocene, metallocene.