Low-dimensional compounds containing cyano groups. XIV. Crystal structure, spectroscopic, thermal and magnetic properties of [CuL2][Pt(CN)4] complexes (L=ethylenediamine or N,N-dimethylethylenediamine)

Violet crystals of [Cu(en)2][Pt(CN)4] and blue crystals of [Cu(dmen)2][Pt(CN)4] were crystallized from the water–methanol solution containing CuCl2·2H2O, ethylenediamine (en) or N,N-dimethylethylenediamine (dmen) and K2[Pt(CN)4]·3H2O. Both compounds were characterized using elemental analysis, infrared and UV-VIS spectroscopy, magnetic measurements, specific heat measurements and thermal analysis. X-ray structure analysis revealed chain-like structure in both compounds. The covalent chains are built of Cu(II) ions linked by [Pt(CN)4]2− anions in the [111] and [101] direction, respectively. The Cu(II) atoms are hexacoordinated by four nitrogen atoms in the equatorial plane from two molecules of bidentate ligands L with average Cu–N distance of 2.022(2) and 2.049(4) Å, respectively. Axial positions are occupied by two nitrogen atoms from bridging [Pt(CN)4]2− anions at longer Cu–N distance of 2.537(2) and 2.600(5) Å, respectively. Both materials are characterized by the presence of weak antiferromagnetic exchange coupling. Despite the one-dimensional (1D) character of the structure, the analysis of magnetic properties and specific heat at very low temperatures shows that [Cu(en)2][Pt(CN)4] behaves as two-dimensional (2D) spatially anisotropic square lattice Heisenberg magnet, while more pronounced influence of interlayer coupling is observed in [Cu(dmen)2][Pt(CN)4].