Chain‐Like Pentanuclear Complexes: Syntheses, Crystal Structures and Long‐Range Electronic Interactions of Cyanido‐Bridged M ₂ Ru ₃ (M=Fe, Ru)

In this work, we report the design and synthesis of two chain-like pentanuclear cyanido-bridged complexes trans-[Ru(bpy)₂(μ-CN)₂][cis-Ru(bpy)₂(μ-NC)M(dppe)Cp*]₂[PF₆]₄ (M=Fe, 1⁴⁺; M=Ru, 2⁴⁺) and the electronic communication properties of their oxidized products 1^m+ (m=6, 7, 8) and 2ⁿ⁺ (n=5, 6, 7, 8). The single-crystal X-ray diffraction analysis of 1^m+ (m=4, 6, 7) and 2⁴⁺ show that 1⁴⁺ and 2⁴⁺ possess a Z-type array structure, 1⁷⁺ is a U-type one, and 1⁶⁺ exhibits both the types. The investigations indicate that both 1 and 2 show an extraordinarily strong electronic interaction between the two side Ru across the central NC-Ru-CN, leading to the formation of a fully delocalized cyanidometal Ru-Ru-Ru bridge for both three-electron oxidized states 1⁷⁺ and 2⁷⁺. Moreover, it should be noted that in 1 there exists no electronic interaction between the two terminal Fe ions. Upon substitution of Fe by Ru, however, 2 exhibits an electronic interaction between the two terminal metal ions across the trinuclear cyanidometal CN-Ru-NC-Ru-CN-Ru-NC bridge which is up to 20 Å.