Novel heterometallic Fe-Ru₂-Fe arrays via "complex of complexes" approach

Four tetranuclear heterometallic compounds, [(Tp)Fe(CN)₃] ₂(Ru₂(DMBA)₄] (1), [(MeTp)Fe(CN) ₃]₂[Ru₂(DMBA)₄] (2), [( ⁱBuTp)Fe(CN)₃]₂[Ru₂(DMBA) ₄] (3), and [(PhTp)Fe(CN)₃]₂[Ru ₂(DMBA)₄] (4) [DMBA = N,N′-dimethylbenzamidinate, Tp = (hydrotris(pyrazolyl)borate, MeTp = (methyltris(pyrazolyl)borate, ⁱBuTp = (2-methylpropyltris(pyrazolyl)borate, and PhTp = (tris(pyrazolyl)phenylborate)] were prepared from the combination of Ru ₂(DMBA)₄(NO₃)₂ and an appropriate [(RTp)Fe(CN)₃]^-. Molecular structures of compounds 1-4 were established using single-crystal X-ray diffraction, and all feature a linear Fe-C≡N-Ru-Ru-N≡C-Fe array. The magnetic study revealed that the temperature dependence of _χMT is mostly attributed to the zero-field splitting of the Ru₂ center, indicating the absence of strong spin coupling among three metallic centers. The electronic independence was further confirmed by the vis-NIR spectroscopic studies. Also described are the voltammetric properties of these compounds.