Synthesis, crystal structure and magnetic propel-ties of the cyano-bridged heteropolynuclear complex [{(Cu(dien))2Co(CN)6}n][Cu(dien)(H2O)Co(CN)6]n•5nH2O

The reaction of [Cu(dien)(H2O)](NO3)(2) with K-3[Co(CN)(6)] leads to the cyano-bridged heteropolynuclear complex, [{(Cu(dien))(2)Co(CN)(6)}(n)][Cu(dien)(H2O)Co(CN)(6)](n). 5nH(2)O, {Cu3Co2}, whose crystal structure has been solved. The structure consists of two distinct ionic units, namely one-dimensional cationic chains [{(Cu(dien))(2)Co(CN)(6)}(n)](n+), and discrete binuclear anionic entities [(H2O)(dien)Cu-NC-Co(CN)(5)](-). The cryomagnetic investigation of the title compound reveals a very weak antiferromagnetic coupling between the Cu(II) ions within the cationic chain (J=-1.02 cm(-1), g=2.14). The complete elimination of the water molecules from the isomorphous {Cu3Co2}, {Cu3Fe2} and {Cu3Cr2} complexes causes the modification of the magnetic properties. The most dramatic one is observed with the Cu(II)-Fe(III) system, where the magnetic behavior changes from ferro- to antiferromagnetic. The dehydrated chromium derivative preserves the ferromagnetic coupling, which is observed at lower temperatures (below 30 K) in comparison with the parent compound (below 150 K). (C) 1999 Elsevier Science Ltd. All rights reserved.