1,2-Diethynylbenzene-Bridged [Cp*(dppe)Fe]^<i>n</i>+ 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 Mössbauer 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, Mössbauer, 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 cation o-1­(PF6) belongs to class IIB of the mixed-valence classification (Hab < 1500 cm–1). The narrowness of the IVCT bands is explained by the steric hindrance, which limits the number of conformers. The singlet/triplet states ratio is independent of the temperature for the doubly oxidized complex o-1­(PF6)2.双核配合物[{Cp*­(dppe)­Fe–C≡C−}₂-μ-(1,2-C₆H₄)] (o-1) 经由双(亚乙烯基)配合物[{(Cp*­(dppe)­Fe=C=CH−}₂-μ-(1,2-C₆H₄)]­(PF₆)₂ (o-1H₂(PF₆)₂) 以优异收率制备得到。该新型配合物采用电喷雾电离质谱（ESI-mass spectrometry）、红外光谱（IR）、多核核磁共振波谱、穆斯堡尔谱学、单晶X射线衍射以及循环伏安法进行了表征。实验数据表明，相邻有机铁中心间存在强烈的空间位阻相互作用，这正是导致o-1制备反应时长极长的原因。单氧化与双氧化形式的o-1(PF₆)和o-1(PF₆)₂，可通过o-1分别与1当量和2当量的二茂铁鎓盐（ferrocenium salt）反应制得。上述盐类采用高分辨电喷雾电离质谱（high-resolution ESI-mass spectra）、单晶X射线衍射分析、红外光谱、穆斯堡尔谱、电子自旋共振波谱（ESR）、紫外-可见光谱（UV–vis）以及近红外光谱（NIR）进行了表征。此外，通过1H和31P核磁共振波谱对双氧化产物o-1(PF₆)₂的磁学性质展开了研究。实验数据依托密度泛函理论（DFT）水平的量子化学计算完成分析。自由基阳离子o-1(PF₆)属于混合价态分类（mixed-valence classification）的IIB类（Hab < 1500 cm⁻¹）。区间电荷转移（IVCT）带的窄化可归因于空间位阻：空间位阻限制了构象异构体的数量。对于双氧化产物o-1(PF₆)₂，其单重态与三重态的比例与温度无关。