Berry Pseudorotation Enabled Photodissociation of Fe(CO)5 Observed by Ultrafast Electron Diffraction

The structural dynamics of metal carbonyls are central to diverse chemical processes, from catalysis to organometallic synthesis. Here we investigate the photodissociation process of a prototypical transition metal carbonyl, Fe(CO) ₅ , using mega-electron-volt ultrafast electron diffraction. By analyzing the structural evolution separately in the axial and equatorial directions of Fe(CO) ₅ , we provide a 3-D atomistic view of the internal conversion process prior to dissociation, and constructed an excited state potential energy surface based on our observation. Additionally, we highlight the significance of wavepacket decoherence preceding the conical intersection, leading to the dissociation of a random carbonyl ligand via Berry pseudorotation mechanism.