1,2-Diethynylbenzene-Bridged [Cp*(dppe)Fe]n+ Units: Effect of Steric Hindrance on the Chemical and Physical Properties

The binuclear complex [{Cp*(dppe)Fe–C≡C−}2-μ-(1,2-C6H4)] (o-1) was prepared via the bis(vinylidene) [{(Cp*(dppe)Fe═C═CH−}2-μ-(1,2-C6H4)](PF6)2 (o-1H2(PF6)2) in good yield. The new complex was characterized by ESI-mass spectrometry, IR, multinuclear NMR, and Mossbauer spectroscopies, X-ray diffraction on a single crystal, and cyclic voltammetry. The data are consistent with a strong steric interaction between the vicinal organoiron centers responsible for the very long time of reaction for the preparation of o-1. The singly and doubly oxidized forms o-1(PF6) and o-1(PF6)2 were prepared by oxidation of o-1 with 1 and 2 equiv of ferrocenium salt. These salts were characterized by high-resolution ESI-mass spectra, XRD analyses on single crystals, and IR, Mossbauer, ESR, UV–vis, and NIR spectroscopies. In addition, the magnetic properties of compound o-1(PF6)2 were investigated by 1H and 31P NMR. The data were analyzed with the support of quantum chemistry calculations at the DFT level of theory. The radical c...