-AMINO-3-METHYL-1,2,4-DELTA(2)-TRIAZOLINE-5-THIONE - AN EXAMPLE OF THIONE-THIOL TAUTOMERISM AND STABILIZATION OF CU(I) AND AU(I) COMPLEXES

Two complexes of Cu(I) (1) and Au(I) (2) with the ligand -amino-3-meth yl-1,2,4-Delta(2)-triazoline-5-thione (HL) have been prepared. Potenti ometric and spectrophotometric studies on the ligand show that the thi ol is the prevalent form in solution while in the solid state the thio ne form is present. Preliminary ab initio calculations of the molecula r electrostatic potential maps for the ligand HL are in good agreement with reactivity and studies in solution. Both compounds crystallize i n the monoclinic system, 1 in the P2(1)/m space group with unit cell p arameters a = 6.829(2), b = 6.218(2), c = 8.540(3) Angstrom, beta = 10 5.68(2)degrees, D-calc = 2.180 g cm(-3) and V = 349.1(2) Angstrom(3) f or Z = 2, 2 in the C2/m space group with unit cell parameters a = 15.9 02(6), b = 6.606(5), c = 6.707(3) Angstrom, beta = 109.37(2)degrees, D -calc = 2.462 g cm(-3) and V = 664.7(6) Angstrom(3) for Z = 2. 563 and 742 observed reflections for 1 and 2, respectively, were used in the refinement which converged to R and R(W) values of 0.0388 and 0.0528 f or 1 and 0.0432 and 0.0540 for 2. The structure of complex 1 presents an unusual phenomenon of disorder with the Cu atoms statistically dist ributed in two independent positions and the complex can be described as assuming a non-molecular cationic structure. The crystal structure of 2 consists of discrete [Au(HL)(2)](+) and Cl- ions.