Interaction of metal ions with allopurinol derivatives. Preparation and structural characterization of methylmercury(II) complexes

Methylmercury(II) complexes of allopurinol (All- H2) and 1-methylpyrazolo [3,4-d] pyrimidin-4-one (MAllH) have been isolated from aqueous solution and structurally characterized. The AllH2 complexes [(CH3Hg)AllH2] NO3 (2), [(CH3Hg)AllH] (3), [(CH3Hg)2All] (4a) and [(CH3Hg)3All]NO3 (5) were prepared at respective pH values of 2, 5, 9 and 5. For MAllH, the complexes [(CH3Hg)MAll] (6a), [(CH3Hg)MAll]·2H2O (6b) and [(CH3Hg)2MAll]- NO3·[(CH3Hg)MAll] (7) could be isolated at pH values of 6–7, 6 and 3–4 respectively. X-ray structural analyses were performed on [AllH3]Cl (1), [(CH3Hg)2All]·2H2O, 4b, 6a, 6b and 7. In the solid state N1, N3 and N8 are protonated in the allo- purinolium cation in 1. N1 and N9 are coordinated in complex 4b. The former nitrogen is also the metal binding site in 6a, 6b and for [(CH3Hg)MAll] in 7. N1, N8-coordination is observed for [(CH3Hg)2- MAIl]+ in the latter species. These structures and 1H NMR data are in accordance with N9-coordination in 2 and 3 and N1, N8, N9-coordination in 5.