EQUILIBRIUM STUDIES OF COPPER(II) AND OF NICKEL(II) COMPLEXES WITH SULPHIDE CONTAINING α,ω-DIAMINES

Abstract
The complex formation of Cu2+ and Ni2+ with 1,7-diaza-4-thiaheptane (2,2-NSN), 1,8-diaza-4-thiaoctane (2,3-NSN), 1,9-diaza-4-thianonane (2,4-NSN) and 1,9-diaza-5-thianonane (3,3-NSN) has been studied potentiometrically at 25°C in 0.5 mol dm−3 (K)NO3 medium. The formation constants of the CuL2+ complexes with the four ligands are 9.02, 10.03, 9.49 and 9.79 respectively. In these 1:1 complexes the ligands can be facially disposed. 2,2-NSN and 2,3-NSN also form a CuL2 2+ complex with log K2=5.24 and 2.86 respectively, whereas the hydrolysis constants of the [Cu(OH)L]+ species with the same ligands are 5.90 and 4.60. 2,3-NSN also forms the species CuHL3+ and CuHL2 3+, with protonation constants 4.77 and 9.7 respectively. With Ni2+ only 5,5- and 5,6-membered chelate ring systems are formed. With 2,2-NSN log K1=7.377 and log K2=6.142. With 2,3-NSN log > K1=5.989 and log K2=3.86. There is a six co-ordinate environment about the metal ion in the NiL2 2+ complexes. The Ni(II) complexes of the latter ligand may be protonated to NiHL3+ and NiHL2 3+ with protonation constants of 6.9 and 8.2 respectively.

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