Crystal Structure and Magnetic Properties of an Infinite Chainlike and a Tetranuclear Bimetallic Copper(II)−Chromium(III) Complex with Bridging Cyanide Ions

Abstract

The crystal structures of two CN- bridged bimetallic copper(II)−chromiun(III) complexes, [{(Cu(dien))2Cr(CN)6}n][Cu(dien)(H2O)Cr(CN)6]n·4nH2O (1) and [(Cu(edma))3Cr(CN)6] (2) (where dien and edma are diethylenetriamine and ethylenediaminemonoacetate respectively), have been determined. Complex 1 (C24H49N21O5Cr2Cu3) crystallizes in the monoclinic system, space group P21/c, with a = 20.509(2) Å, b = 14.376(3) Å, c = 15.040(4) Å, β = 96.03(2),° and Z = 4. In the crystal structure, complex 1 has two distinct ionic units: one is a cationic polymeric chain formed by [(Cu(dien))2Cr(CN)6]+ and the other is a CN--bridged binuclear anion [(Cu(dien)(H2O)Cr(CN)6]-. Complex 2 crystallizes in the trigonal system, space group R3C, with a = 24.446(2) Å, b = 14.446(2) Å, c = 22.685(1) Å, and Z = 6. Complex 2 consists of discrete tetranuclear molecule [(Cu(edma))3Cr(CN)6]-. In both complexes, the Cr atoms all have an octahedral configuration with six coordinated CN- ions and connect to the copper atoms via the CN- ions. At higher temperature, the χT of both complexes increases with decreased temperature showing the ferromagnetic behavior which is due to the ferromagnetic exchange interaction between Cu and Cr atoms through the bridging CN- ions. However at lower temperature, χT decreases with decreased temperature; this can be attributed to the occurrence of the antiferromagnetic intramolecular interaction (zJ‘). The fitting to the experimental magnetic susceptibilities gives g = 2.10, Ja = 7.24 cm-1, Jc = 6.41 cm-1, and zJ‘ = −0.16 cm-1 for 1 and g = 2.09, J = 9.16 cm-1, and zJ‘ = −0.09 cm-1 for 2.