OBSERVATIONS ON THE CONFORMATION OF IMINODIACETATE(2-) ION IN MIXED-LIGAND COPPER(II) COMPLEXES WITH NITROGEN-HETEROCYCLES AS SECONDARY LIGANDS - CRYSTAL-STRUCTURE OF (2,2'-BYPIRIDINE)(IMINODIACETATO)COPPER(II) HEXAHYDRATE

(2,2'-Bipyridine)(iminodiacetato)copper(II) hexahydrate, [Cu(IDA)(2,2'-bipy)].6H(2)O, has been obtained and studied by X-ray diffraction. The compound (triclinic system, space group P1, Z = 2; R = 0.036 and R = 0.040 for 7541 independent reflections) consists of asymmetric dinuclear entities, [Cu(IDA)(2,2'-bipy)](2), and uncoordinated H2O molecules in a hydrogen bonding network. Both Cu(II) atoms of each dinuclear entity are chemically very similar. Each Cu(II) atom exhibits a flattened, square pyramidal coordination. Two N atoms of 2,2'-bipy and the N and one O atoms of IDA are at the square base; another O atom of the same terdentate IDA is at the apical position. Two weak interactions between each Cu(II) atom and one O atom from IDA which chelates the second contribute to the dinuclear entity. On the basis of these results and the known structure of other Cu(II) complexes with IDA and imidazole or 4,4'-bipy, an attempt to rationalize the nearly coplanar or perpendicular conformation of the two five-membered IDA-Cu(II) chelate rings in such mixed-ligand copper(II) complexes is made.