Inner orbital splitting in some 3 d n transition metal complexes with oxygen, sulphur and nitrogen donor ligands

Abstract

The thermodynamic equilibrium constants of the 3 d n transition metals [Zn 2−(3 d 10), Cu 2−(3 d 9), Ni 2+(3 d 8), Co 2+(3 d 7), and Mn 2+(3 d 5)] complexes with the oxygen donor ligand 5.5' thiodisalicylic acid (TDSH 4) and sulphur donor ligand α-mercaptopropionic acid (MPA) have been determined potentiometrically at 35±0.1°C. The thermodynamic parameters Δ G, Δ H and Δ S have been calculated. The nitrogen donor ligand biuret (BT) has been included here for comparative studies of the complexing behaviour. The transition series contraction energy E r (Mn-Zn) and thermodynamic ligand field stabilization energy “δ H” of the metal complexes have been evaluated. The inner orbital splitting values of the complexes show the order for the ligand activity to be BT>TDSH 4>MPA≅H 2O.