Interaction of Metal Ions with 7-Deaza-8-aza- and 8-Aza-purines Preparation and X-Ray Structural Analysis of Copper(II) Complexes

Fachbereich Chemie der Universität Kaiserslautern, Erwin-Schrödinger-Straße, D-6750 Kaiserslautern Z. Naturforsch. 42b, 195-202 (1987); received August 18/October 17, 1986 8-Azapurines, Allopurinol, Copper(II) Complexes, X-Ray The reaction of 8-azaand 7-deaza-8-aza-purines with Cu : + cations in acid solution has been studied. At a pH value of 2, the 8-azaadenine complex [Cu(H20)4(AAdH)2](N03)2 (1), which displays C u N 9 coordination, may be isolated from solution. The reaction of CuCl2 with 8-azahypoxanthine in concentrated HCl solution leads to ring opening at C 2 of the azapurine with subsequent formation of dichlorobis[(5-amino-4-carboxamide)[l — 3]triazole] copper(II) dihydrate 2, in which the triazole ligands display a chelating function, coordinating the metal via N7 and 0 6 . The results for 1 and 2 suggest that copper coordination of the azapurine base is not a prerequisite for opening of the pyrimidine ring. Respectively N9and N8-coordinated complexes [ C U C 1 3 ( A 1 1 H 3 ) ] „ 3 and [CuCl2(H20)(MAllH)]n (4) of allopurinol (A11H2) and 9-methylallopurinol (MA11H) may be prepared by the reaction of CuCl2 with the respective bases in HCl solution. In contrast, with the analogous l-methyl-4-aminopyrazolo[3,4-d]pyrimidine MAPP, only the salt ( M A P P H ) 4 ( C U 2 C 1 8 ) (5) could be isolated under similar conditions, indicating that N8 is less attractive as a binding site in this 7-deaza-8-azaadenine derivative. The structures of 1—5 have been established by X-ray structural analysis. A distorted octahedral [4+2]geometry is found for the copper atoms in 1 and 2. Chlorine bridged polymeric chain structures are adopted by the complexes 3 and 4. An intermediate coordination geometry between trigonal bipyramidal and square-pyramidal is observed for the metal atoms in 3, a distorted square-pyramidal geometry in 4.