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. Th e compound (triclinic system, space group P1, Z = 2; R = 0.036 and R = 0.040 for 7541 independent reflections) consists of asymmetric dinucl ear entities, [Cu(IDA)(2,2'-bipy)](2), and uncoordinated H2O molecules in a hydrogen bonding network. Both Cu(II) atoms of each dinuclear en tity are chemically very similar. Each Cu(II) atom exhibits a flattene d, square pyramidal coordination. Two N atoms of 2,2'-bipy and the N a nd one O atoms of IDA are at the square base; another O atom of the sa me terdentate IDA is at the apical position. Two weak interactions bet ween each Cu(II) atom and one O atom from IDA which chelates the secon d contribute to the dinuclear entity. On the basis of these results an d the known structure of other Cu(II) complexes with IDA and imidazole or 4,4'-bipy, an attempt to rationalize the nearly coplanar or perpen dicular conformation of the two five-membered IDA-Cu(II) chelate rings in such mixed-ligand copper(II) complexes is made.