A missing high-spin molecule in the family of cyanido-bridged heptanuclear heterometal complexes, [(LCuII)6FeIII(CN)6]3+, and its CoIII and CrIII analogues, accompanied in the crystal by a novel octameric water cluster

Three isostructural cyanido-bridged heptanuclear complexes, [{Cu II(saldmen)(H2O)}6{MIII(CN) 6}](ClO4)3·8H2O (M = Fe III2; CoIII, 3; CrIII4), have been obtained by reacting the dinuclear copper(ii) complex, [Cu2(saldmen) 2(μ-H2O)(H2O)2](ClO 4)2·2H2O 1, with K3[Co(CN) 6], K4[Fe(CN)6], and K3[Cr(CN) 6], respectively (Hsaldmen is the Schiff base resulting from the condensation of salicylaldehyde with N,N-dimethylethylenediamine). A unique octameric water cluster, with bicyclo[2,2,2]octane-like structure, is sandwiched between the heptanuclear cations in 2, 3 and 4. The cryomagnetic investigations of compounds 2 and 4 reveal ferromagnetic couplings of the central Fe III or CrIII ions with the CuII ions (J CuFe = +0.87 cm-1, JCuCr = +30.4 cm -1). The intramolecular Cu⋯Cu exchange interaction in 3, across the diamagnetic cobalt(iii) ion, is -0.3 cm-1. The solid-state 1H-NMR spectra of compounds 2 and 3 have been investigated.