Multistate-Mediated Rearrangements and FeCl2 Elimination in Dinuclear FePd Complexes.

Mass spectrometric, spectroscopic, and computational characterization of a novel bifunctional iron-palladium complex proves a change of coordination upon solvation. Collisional excitation reveals FeCl2 and HCl elimination in a solvent-modulated competition. Hereby, syn and anti isomers, identified by theoretical calculations, favor and disfavor FeCl2 elimination, respectively. The FeCl2 elimination likely proceeds by chlorido and Cp ligand exchange among the metallic centers in a concerted, ballet-like manner. A multitude of stationary points were identified along the computed multistep reaction coordinates of the three conceivable spin states. The quintet state shows a static Jahn-Teller type relaxation by a tilt away of the Cp ligand at the iron center. The direct singlet-quintet spin crossover is an unprecedented assumption, leaving behind the triplet state as a spectator without involvement. The FeCl2 elimination would decrease catalytic activity. It is kinetically hindered within a range of applicable temperatures in conceivable technical applications.