Organocobalt chemistry

Organocobalt compounds are involved in several organic reactions and the important biomolecule vitamin B12 has a cobalt-carbon bond.

Many organocobalt compounds exhibit useful catalytic properties, the preeminent example being dicobalt octacarbonyl.

These synthetic compounds also form alkyl derivatives that undergo diverse reactions reminiscent of the biological processes.

In the Nicholas reaction an alkyne group is also protected and at the same time the alpha-carbon position is activated for nucleophilic substitution.

A famous sandwich compound is cobaltocene, a rare example of low-spin Co(II) complex.

Cobalt catalysts (together with iron) are relevant in the Fischer–Tropsch process in which it is assumed that organocobalt intermediates form.

Although really only dicobalt octacarbonyl has achieved commercial success, many reports have appeared promising applications.

Vitamin B12 and related cofactors are organocobalt compounds.
Vitamin B12 and related cofactors are organocobalt compounds.
Co(4-norbornyl) 4 is a rare example of a low-spin tetrahedral complex and a rare case of an organocobalt(V) derivative. [ 2 ]
Co(1,5-cyclooctadiene)(cyclooctenyl).
Mechanism proposed for trimerisation of alkyne to give arenes.
Mechanism proposed for trimerisation of alkyne to give arenes.
Mechanism of cobalt-catalyzed hydroformylation. The process begins with dissociation of CO from cobalt tetracarbonyl hydride to give the 16-electron species (step 1 ). Subsequent binding of alkene gives an 18e species (step 2 ). In step 3 , the olefin inserts to give the 16e alkyl tricarbonyl. Coordination of another equivalent of CO give alkyl tetracarbonyl (step 4 ). [ 8 ] Migratory insertion of CO gives the 16e acyl in step 5 . In step 6 , oxidative addition of hydrogen gives a dihydrido complex, which in step 7 releases aldehyde by reductive elimination . [ 9 ] Step 8 is unproductive and reversible.