A missing high-spin molecule in the family of cyanido-bridged heptanuclear heterometal complexes, [(LCu(II))(6)Fe(III)(CN)(6)](3+), and its Co(III) and Cr(III) analogues, accompanied in the crystal by a novel octameric water cluster

Abstract

Three isostructural cyanido-bridged heptanuclear complexes, [{Cu(II)(saldmen)(H(2)O)}(6){M(III)(CN)(6)}]( ClO(4))(3)center dot 8H(2)O (M = Fe(III) 2; Co(III), 3; Cr(III) 4), have been obtained by reacting the dinuclear copper(II) complex, [Cu(2)(saldmen)(2)(mu-H(2)O)(H(2)O)(2)](ClO(4))(2)center dot 2H(2)O 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 center dot center dot center dot 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.