Thermodynamic and Kinetic Factors of the Structure Formation of Bis-Chelate Complexes of Ni(II) with o-Hydroxy- and o-Mercaptoazobenzamides: A Quantum Chemical Study

The molecular structures and relative energies of the low-spin bis-chelate Ni(II) complexes with o-hydroxy- and o-mercaptoazobenzene ligands were calculated using density functional theory, taking into account the possibility of forming trans- and cis-isomeric structures with six- and five-membered metallacycles. The kinetic factor governing the structure formation of NiL₂ complexes was analyzed using a stepwise model of their formation (Ni⁺⁺ + (L)^– → (NiL)⁺, (NiL)⁺ + (L)^– → NiL₂). The results show that the most favorable isomer of the complexes is determined not only by the energy advantage of a particular configuration, but also by its kinetic accessibility, which is governed by the activation barriers of the isomerization reactions of the products formed at the first step of the interaction of the initial reagents.