Discrete Rh<sup>III</sup>/Fe<sup>II</sup> and Rh<sup>III</sup>/Fe<sup>II</sup>/Co<sup>III</sup> Cyanide-Bridged Mixed Valence Compounds
作者:Paul V. Bernhardt、Manuel Martínez、Carlos Rodríguez、Marta Vazquez
DOI:10.1021/ic102061s
日期:2011.2.21
The heterotrinuclear complexes trans- and cis-[cis-VI-L15RhIII(mu-NC)}trans-III-L14SCoIII(mu-NC)}Fe-II(CN)(4)](2+) are unprecedented examples of mixed valence complexes based on ferrocyanide bearing three different metal centers. These complexes have been assembled in a stepwise manner from their trans-III-L14SCoIII}, cis-VI-L15RhIII}, and Fe-II(CN)(6)} building blocks. The preparative procedure follows that found for other known discrete assemblies of mixed valence dinuclear Cr-III/Fe-II and polynuclear Co-III/Fe-II complexes of the same family. A simple slow substitution process of [Fe-II(CN)(6)](4-) on inert cis-VI-[(RhL15)-L-III(OH)](2+) leads to the preparation of the new dinuclear mixed valence complex [cis-VI-L15RhIII(mu-NC)}Fe-II(CN)(5)](-) with a redox reactivity that parallels that found for dinuclear complexes from the same family. The combination of this dinuclear precursor with mononuclear trans-III-[(CoL14SCl)-L-III](2+) enables a redox-assisted substitution on the transient L14SCoII} unit to form [cis-VI-L15RhIII(mu-NC)}trans-III-(L14SCoL14SCoIII)-L-III (mu-NC)} Fe-II(CN)(4)](2+). The structure of the final cis-[cis-VI-L15RhIII(mu-NC)}trans-III-L14SCoIII(mu-NC)}Fe-II(CN)(4)](2+) complex has been established via X-ray diffraction and fully agrees with its solution spectroscopy and electrochemistry data. The new species [cis-VI-L15RhIII(mu-NC)}trans-III-L14SCoIII(mu-NC))Fe-II(CN)(4)](2+) and [cis-VI-L15RhIII(mu-NC)} Fe-II(CN)(5)](-) show the expected electronic spectra and electrochemical features typical of Class II mixed valence complexes. Interestingly, in the trinuclear complex, these features appear to be a simple addition of those for the Rh-III/Fe-II and Co-III/Fe-II moieties, despite the vast differences existant in the electronic spectra and electrochemical properties of the two isolated units.