Self-assembly of tetrahedral and trigonal antiprismatic clusters [Fe₄(L⁴)₄] and [Fe₆(L⁵)₆] on the basis of trigonal tris-bidentate chelators

In a one-pot reaction, the tetranuclear iron chelate complex [Fe₄(C⁴)₄] 6 was generated from benzene-1,3,5-tricarboxylic acid trichloride (4), bis-tert-butyl malonate (5a), methyllithium, and iron(II) dichloride under aerobic conditions. Alternatively, hexanuclear iron chelate complex. [Fe₆(L⁵)₆] 7 was formed starting from bis-para-tolyl malonate (5b) by employing identical reaction conditions to those applied for the synthesis of 6. The clusters 6 and 7 are present as racemic mixtures of homoconfigurational (Δ,Δ,Δ,Δ)/(Λ,Λ,Λ,Λ)-fac or (Δ,Δ,Δ,Δ,Δ,Δ)/ (Λ,Λ,Λ,Λ,Λ,Λ)-fac stereoisomers. The structures of 6 and 7 were unequivocally resolved by single-crystal X-ray analyses. The all-iron(III) character of 6 and 7 was determined by Mössbauer spectroscopy.