Mechanism of the Formation of trans- and cis-Isomers of the Bis(chelate) Pd(II) and Pt(II) Complexes Based on (N,O(S,Se))-Bidentate Azomethines: A Quantum Chemical Study

The molecular structures and relative energies of trans- and cis-isomers of bis(chelate) complexes of Pd(II) and Pt(II) salicylal-, thiosalicylal-, and selenosalicylaldiiminates are calculated using the density functional theory. The role of the kinetic factor in the formation of the trans- and cis-isomers of the PdL₂ and PtL₂ complexes is studied in the framework of the model of the step-by-step formation of the bis(ligand) metal complexes ML₂ (M⁺⁺ + (L)^– → (ML)⁺, (ML)⁺ + (L)^–→ ML₂). The competition of the trans- and cis-isomers of the PdL₂ and PtL₂ bis(chelate) azomethine complexes with the coordination nodes MN₂O₂, MN₂S₂, and MN₂Se₂ is shown to be determined by both the energy preference of one of possible configurations and activation barriers of the isomerization of the products formed in the first step of the interaction of the initial reagents.