Kristallstrukturen der Terpyridin-Komplexe [Cd(terpy)Cl2], [Cu(terpy)(CN)Cl] und [Cu(terpy)][Cu(CN)3] · H2O

Crystal Structures of the Terpyridine Complexes [Cd(terpy)Cl₂], [Cu(terpy)(CN)Cl], and [Cu(terpy)][Cu(CN)₃] · H₂O By reaction of cadmium chloride with 2,2′ : 6′,2″-terpyridine (“terpy”) in water/acetone crystals of [Cd(terpy)Cl₂] ( 1) were formed. The compound crystallizes monoclinic, space group P2₁/c, a = 1111.70(10), b = 823.10(7), c = 1643.00(14) pm, β = 93.913(1)°, Z = 4. Starting from mixtures of different molar ratios of copper(II) chloride, terpyridine, and KCN in water/methanole, two complexes of different composition were obtained. At the molar ratio of 1 : 1 : 2 a copper(II) coordination compound with both halide and pseudohalide ligands, [Cu(terpy)(CN)Cl] ( 2 ), was formed which also crystallizes monoclinic, P2₁/c, a = 1065.6(3), b = 824.6(2), c = 1644.5(7) pm, β = 98.214(3)°, Z = 4. At a molar ratio of 1 : 1 : 10 a partial reduction of copper(II) occured with formation of a mixed valency compound [Cu(terpy)][Cu(CN)₃] · H₂O ( 3 ) which crystallizes in the hexagonal space group P6₅22, with a = b = 800.29(1), c = 4771.05(7) pm, Z = 6. Compounds 1 and 2 are structurally similar, the coordination of the metal atoms is square pyramidal. Networks are formed by hydrogen bridges. In 3 the copper(II) ions show a distorted square planar coordination by the three N atoms of the terpy ligand and one N atom of a bridging CN^– group, the copper(I) atoms, however, show trigonal planar coordination by three CN^– ligands to which the water molecules are bonded by hydrogen bridges. Thus helical chains are formed which stretch in the direction of the screw axes. The EPR spectrum of 3 was measured.