A missing high-spin molecule in the family of cyanido-bridged heptanuclear heterometal complexes, [(LCu~(II))_6Fe~(III)(CN) _6]~(3+), and its Co~(III) and Cr~(III) analogues, accompanied in the crystal by a novel octameric water cluster

摘要

Three isostructural cyanido-bridged heptanuclear complexes, [{Cu ~(II)(saldmen)(H_2O)}_6{M~(III)(CN) _6}](ClO_4)_3·8H_2O (M = Fe ~(III)2; Co~(III), 3; Cr~(III)4), have been obtained by reacting the dinuclear copper(ii) complex, [Cu_2(saldmen) _2(μ-H_2O)(H_2O)_2](ClO _4)_2·2H_2O 1, with K_3[Co(CN) _6], K_4[Fe(CN)_6], and K_3[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 Cr~(III) ions with the Cu~(II) ions (J _(CuFe) = +0.87 cm~(-1), J_(CuCr) = +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.