2020 Volume 69 Issue 5 Pages 137-139
Effect of ligand field on cation forming complexes with precipitation inhibitors for metallic corrosion in aerated neutral solution are discussed based on the hard and soft acids and bases (HSAB) principle. The energy levels of three 3d orbitals, dxy, dxz and dyz in Fe3+, for example, decrease and two orbitals, dx2-y2 and dz2 increase markedly by approaching an effective ligand, :CN-, resulting in the formation of d2sp3 hybrid orbital. Contrary, less effective ligand like :NH3 provides sp3d2 hybrid orbital. Because chelating agents enhance the ligand field effect markedly, the d2sp3 hybrid orbital of Fe3+ can be provided for the formation of chelate compound, resulting in stable coordinate bonds between hard acid and hard base.