Tetra-, Penta-, and Hexacoordinate Stereoisomers of the Bis(ligand) Complexes of Zn(II) and Cd(II) Based on (N,O,S(Se))-Tridentate Azomethines. A Quantum Chemical Study

The molecular structures and relative energies of tetra-, penta-, and hexacoordinate stereoisomers of the Zn(II) and Cd(II) bis(ligand) complexes based on (N,O,Y (Y = S, Se))-tridentate azomethines (coordination nodes of the competing stereoisomers are MN2O2, MN2O2Y, and MN2O2Y2, respectively) are calculated by the density functional theory and nonempirical Hartree–Fock method. The simulation of the mechanism for the formation of the tetra-, penta-, and hexacoordinate stereoisomers with allowance for the subsequent stereoisomerization makes it possible to establish the preferable tetracoordination (as a pseudotetrahedron) for the zinc complexes and penta- or hexacoordination for the cadmium complex depending on the specific features of the ligand structure.