Ferrocenecarboxylic acid
Ferrocenecarboxylic acid is the organoiron compound with the formula .  It is the simplest carboxylic acid derivative of ferrocene.  It can be prepared in two steps from ferrocene by acylation with a 2-chlorobenzoyl chloride followed by hydrolysis.

Reactions and derivatives
The pKa of ferrocenecarboxylic acid is 7.8.  The acidity increases more than a thousand-fold, to pH 4.54 upon oxidation to the ferrocenium cation.

By treatment with thionyl chloride, the carboxylic acid anhydride () is produced.

Derivatives of ferrocenecarboxylic acid are components of some redox switches.

Related compounds
 1,1'-Ferrocenedicarboxylic acid

References

Ferrocenes
Cyclopentadienyl complexes
Carboxylic acids