Synthesis and characterization of Co(II), Ni(II), Cu(II) and Zn(II) complexes of 4-amino-1,2,4-triazolidine-3,5-dione (urazine)

The complexing capability of urazine as neutral (Hur) or monoanionic (ur) l igand towards divalent cations (Co, Ni, Cu, Zn) was examined. Complexes CoC l2(Hur)(2). 4H(2)O (1), NiCl2(Hur)(2). 4H(2)O (2) and Zn(SO4)(Hur). 2H(2)O (3), in which urazine acts as neutral ligand, were synthesized and characte rized. It is worth noting that in the examined crystal the chiral complex 3 shows only the A enantiomer due to a spontaneous resolution. Complexes Co( ur)(2). 4H(2)O (4), NiCl(ur).H2O (5), CuCl(ur). 2H(2)O (6) and Zn(ur)(2). 2 H(2)O (7), in which coordinated deprotonated urazine molecules are present, were synthesized in aqueous solution starting from the urazine sodium salt . Other copper(II) complexes Cu-3(NO3)(2)(ur)(4). 6H(2)O (8), Cu(ur)(2). 4H (2)O (9), Cu-2(SO4)(ur)(2). 2H(2)O (10) were synthesized in aqueous solutio n starting from the free ligand. The crystal structures of 1, 3, 8, 9, 10 w ere determined by X-ray diffraction methods. In the structurally characteri zed complexes Hur acts only as N,O chelating agent in 1 and 3, whereas ur a cts as monodentate through the deprotonated triazolidine nitrogen atom in 9 , tridentate in 8 and tetradentate in 8 and 10. (C) 2000 Elsevier Science B .V. All rights reserved.