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

The crystal structures of two CN - bridged bimetallic copper(II)−chromiun(III) complexes, [{(Cu(dien)) 2 Cr(CN) 6 } n ][Cu(dien)(H 2 O)Cr(CN) 6 ] n ·4 n H 2 O ( 1 ) and [(Cu(edma)) 3 Cr(CN) 6 ] ( 2 ) (where dien and edma are diethylenetriamine and ethylenediaminemonoacetate respectively), have been determined. Complex 1 (C 24 H 49 N 21 O 5 Cr 2 Cu 3 ) crystallizes in the monoclinic system, space group P 2 1 / 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)) 2 Cr(CN) 6 ] + and the other is a CN - -bridged binuclear anion [(Cu(dien)(H 2 O)Cr(CN) 6 ] - . Complex 2 crystallizes in the trigonal system, space group R 3 C, 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)) 3 Cr(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 χ T 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, χ T 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, J a = 7.24 cm - 1, J c = 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 .