(Electrochemical) Properties and Computational Investigations of Ferrocenyl-substituted Fe(μ-PFc)(CO) and Co(μ-PFc)(CO) Clusters and Their Reduced Species.

The formation of ferrocenyl-functionalized iron and cobalt carbonyl clusters is reported, based on a reaction of FcPCl () (Fc = Fe(η-CH)(η-CH)) with Fe(CO) and Co(CO), respectively. Therein, Fe(CO)(μ-PFc) () and Co(CO)(μ-PFc) () clusters were obtained as the first diferrocenyl-substituted carbonyl clusters with a symmetrical cluster core. Cluster shows two reversible one-electron processes within the anodic region, based on Fc/Fc redox events, as well as two processes in the cathodic region. In situ IR and electron paramagnetic resonance (EPR) measurements of all electronic states confirmed an Fc-based oxidation and a core-based reduction. On the basis of the results of a single-crystal X-ray analysis of structures of and , computational studies of the highest occupied molecular orbital-lowest unoccupied molecular orbital energies, the spin density, quantum theory of atom-in-molecule delocalization indices, and the atomic charges were performed to explain the experimental results. The latter revealed a reorganization of the cluster core upon reduction and the existence of weak P···P interactions in and . Ferrocenyl-related redox processes, occurring reversibly in case of , were absent for , due to a different distribution of the HOMO energies. EPR measurements furthermore confirmed the core-based radical anion and the formation of a decomposition product at potentials lower than [M] (M = Fe, Co).