The solid decomposes slowly in air, and thus samples are typically stored cold under an inert atmosphere.

It was occasionally obtained from the thermolysis of Fe(CO)5: Traces of the compound are easily detected because of its characteristic deep green colour.

Early evidence for its distinctive C2v structure came from Mössbauer spectroscopic measurements that revealed two quadrupole doublets with similar isomer shifts but different (1.13 and 0.13 mm s−1) quadrupolar coupling constants.

Ten of the CO ligands are terminal and two span an Fe---Fe edge, resulting in C2v point group symmetry.

Fe3(CO)12 reacts with thiols and disulfides to give thiolate-bridged complexes, such as methylthioirontricarbonyl dimer:[6] Fe3(CO)12 is hazardous as a source of carbon monoxide.