^2-as a Conduit of Electronic Effects: Comparative Studies of Fe···Fe Communication in [{(η⁵-Cp)(dppe)Fe}₂{μ₂-(NC-X-CN)}]ⁿ⁺(n = 0, 2)

Electronic communication between Fe centers in the diiron complexes [{(η5-Cp)(dppe)Fe}2{μ2-(NC-X-CN)}]n+ (n = 0, 2) in which X = [-B10H8-]2-,-C6H4-,-C8H12-, and-C2B10H10-was investigated by spectroscopic (UV-vis and IR), electrochemical (CV and DPV), and single-crystal XRD methods. All experimental results were supported by a DFT computational analysis (B3LYP/Def2SVP) of model complexes that included two other closo-boranes: X =-C2B8H8-and [-B12H10-]2-. The DFT analysis focused on the geometry, electronic excitations, IR spectra, charge and spin delocalization, and intramolecular spin-spin exchange interactions in the series of all six complexes and their singly and doubly oxidized analogues. The results demonstrate that [closo-B10H8-1,10-diyl]2- has the best ability among the closo-boranes to mediate electronic effects similar to those of 1,4-phenylene. This is evident from the observed separation of one-electron-oxidation waves (â 70 mV) and comparable S-T energy gaps in the doubly oxidized species.