FeMo Heterobimetallic Dithiolate Complexes: Investigation of Their Electron Transfer Chemistry and Reactivity toward Acids, a Density Functional Theory Rationalization.

The electrochemical behavior of complexes [FeMo(CO)5(κ2-dppe)(µ-pdt)] (1) and [FeMo(CO)4(MeCN)(κ2-dppe)(µ-pdt)] (2), in the absence and in the presence of acid, has been investigated. The reduction of 1 follows at slow scan rates, in CH2Cl2-[NBu4][PF6] and acid-free media, an ECrevE mechanism that is supported by cyclic voltammetry (CV) experiments and digital CV simulations. In MeCN-[NBu4][PF6], the electrochemical reduction of 1 is the same as in dichloromethane and follows an ECE mechanism at slow scan rates, but with a positive shift of the redox potentials. In contrast, the oxidation of 1 is strongly solvent-dependent. In dichloromethane, the oxidation of 1 is reversible and involves a single electron, while in acetonitrile, it is irreversible at moderate and slow scan rates ( v ≤ ca. 1 V s-1), and some chemical reversibility is apparent at higher scan rates ( v = 10 V s-1). Density functional theory calculations revealed that the chemical step in the ECrevE mechanism corresponds to the dissociation of one PPh2 end of the diphosphine ligand and the transfer of the semibridging CO to the Fe atom, similarly to the mechanism observed in the FeFe analogue complex. However, in the case of 1, the subsequent coordination of the phosphine ligand to the other metal is an unfavorable process.

A new FeMo complex as a model of heterobimetallic assemblies in natural systems: Mössbauer and density functional theory investigations.

The design of the new FeMo heterobimetallic species [FeMo(CO)5(κ(2)-dppe)(µ-pdt)] is reported. Mössbauer spectroscopy and density functional theory calculations give deep insight into the electronic and structural properties of this compound.