Polynuclear thiolate complexes in solution. Solution equilibria studies of silver(I) complexes of 4-mercapto-1-methylpiperidine

Polynuclear complex formation at 25 °C in 2 mol dm-3 NaNO3 (10% v/v MeOH) between AgI and 4-mercapto-1-methylpiperidine has been studied by means of two different sets of titrations. The first set allows one to establish that [Agp(AH)q]p+ species with the p,q values 12,12; 10,9; 8,6; 7,6; 6,4; and 6,3 are present in strongly acidic solutions, AH being the monoprotonated ligand. The second set indicates that at increasing pH values, pH ≤ 8.5, the only species with p = q, [Ag12(AH)12]12+, coexists and eventually transforms into complexes with p < q: 7,8; 6,8; 2,3; and 1,3. In both cases, graphical methods were applied prior to the mathematical treatment of data. An adaptation of the extended-variation method to metal electrode data has been carried out.