Mono- and disubstituted ferrocenes react with excess mercuric acetate (at least eight or nine equivalents) to afford highly insoluble mixtures of polymercurated ferrocenes. In the case of 1,1 -dimethylferrocene, the mercurated product is composed of minor amounts of the octamercurated and hexamercurated ferrocenes, with the heptamercurated ferrocene being the major product. This analysis is based upon results of chlorination and bromination studies of the mercurated species. It is proposed that exhaustive mercuration fails due to the extreme insolubility of the higher mercurated products.