The behaviour of iron carbonyl, Fe(CO)5, at high pressure

Iron pentacarbonyl is an iconic molecule with widespread applications in organometallic chemistry. However, its behaviour at non-ambient conditions is poorly known. In 2020 we carried out a low-temperature study using HRPD, from which we identified a new polymorph that becomes stable below 105 K. At high pressure, there is only a single study carried out in a diamond anvil cell using Raman spectroscopy [Ryu et al., Sci. Rep., 5, 15139: 2015], which found two high-P polymorphs, phases II and III, followed by decomposition at ~ 15 GPa. We aim to test the hypothesis that our low-T structure corresponds with the first high-pressure polymorph (phase II, stable above 1 GPa at room temperature), to determine the structure of the unknown phase III (stable above 5 GPa at room-T), and to measure the equations of state of phases I, II and III.