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)Cl-2] (1) were formed. The compound crystallizes monoclinic, space group P2(1)/c, a=1111.70(10), b=823.10(7), c = 1643.00(14) pm, beta = 93.913(1)degrees 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, P2(1)/c, a = 1065.6(3), b = 824.6(2), c = 1644.5(7) pm, beta = 98.214(3)degrees, 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 P6(5)22, 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.