MIXED COMPLEXES OF 5-NITROSOURACIL DERIVATIVES - SYNTHESIS AND STRUCTURAL STUDY OF 6-AMINO-1,3-DIMETHYL-5-NITROSOURACILATO (N-5,N-6)-AQUA-2,2'-BIPYRIDINE (N,N')-COPPER(II) PERCHLORATE HYDRATE AND 2,2'-BIPYRIDINE (N,N')-CHLORO-1,3-DIMETHYLVIOLURATO (N-5,O-6)-COPPER(II) HEMIHYDRATE

The mixed [Cu(DANU)(bipy)(H2O)]ClO4 . H2O (1) and [Cu(DMV)(bipy)Cl]. 1 /2H(2)O (2) complexes have been isolated from the reaction, in water/E tOH medium, of copper(II) perchlorate and chloride with 6-amino-1,3-di methyl-5-nitrosouracil (HDANU) and 2,2'-bipyridine (bipy). It is notew orthy that, in the second complex, the uracil ligand is the 1,3-dimeth yl-violurato monoanion (DMV), appeared from the hydrolysis of HDANU. I n addition to X-ray diffraction studies, these compounds have been cha racterized from IR and EPR spectra and magnetic measurements (77-290 K ). The crystal lattice of 1 is made up of discrete square pyramidal [C u(DANU)(bipy)(H2O)](+) cations, a disordered perchlorate group and a w ater molecule. The coordination geometry about the metal centre is squ are pyramidal (N-4+O). The basal positions are occupied by a bidentate DANU ligand, coordinated through the N15 and N16 donor positions, and a bipyridine ligand. A water molecule (Cu-O1W 2.193(3) Angstrom) occu pies the apical site. The compound 2 presents a similar molecular stru cture to that of 1 with the copper centre lying in a N3O+Cl environmen t. In this case,the basal positions are occupied by a bipy ligand and a DMV ligand coordinated through the N15 and O16 donor positions, inst ead of the DANU ligand found in the previous compound. The apical posi tion is occupied in this case by a chlorine atom (Cu1-Cl1 2.413(2) and Cu2-Cl2 2.389(2) Angstrom). (C) 1998 Elsevier Science Ltd. All rights reserved.