Rhodocene is an organometallic compound with the formula [Rh(C5H5)2]. Each molecule contains an atom of rhodium bound between two planar systems of five carbon atoms known as cyclopentadienyl rings in a sandwich arrangement. The [Rh(C5H5)2] radical is found above 150 °C or when trapped by cooling to liquid nitrogen temperatures (−196 °C). At room temperature, pairs of these radicals join via their cyclopentadienyl rings to form a dimer, a yellow solid. Biomedical researchers have examined the applications of rhodium compounds and their derivatives in medicine and reported one potential application for a rhodocene derivative as a radiopharmaceutical to treat small cancers. Rhodocene derivatives are also used to study metal–metal interactions in linked metallocenes which can potentially be used to make molecular electronics. Rhodocene can be synthesized by reacting rhodium chloride hydrate, cyclopentadiene, and ammonium hexafluorophosphate. (Full article...)