[<i>closo</i>-B₁₀H₈-1,10-(CN)₂]^2– as a Conduit of Electronic Effects: Comparative Studies of Fe···Fe Communication in [{(<i>η</i>^<i>5</i>-Cp)(dppe)Fe}₂{μ_<i>2</i>-(NC-X-CN)}]^<i>n</i>+ (<i>n</i> = 0, 2)

Abstract

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 (∼70 mV) and comparable S–T energy gaps in the doubly oxidized species.