Abstract:

Structures of the mononuclear complex Ir(CO)Cl(Ph2Ppy)2(1), binuclear complexes Ir(CO)(Cl)2(Ph2Ppy)2·HgCl (2), Ir (CO)Cl (Ph2Ppy)2HgCl2 (3), and Ir (CO) (Cl)2 (HgCl2) (Ph2Ppy)2HgCl (4) were optimized using the density functional theory (DFT) PBE0 method with SDD basis sets for Ir and Hg, 6-31G* basis sets for H, C, O, and N atoms and 6-311G* basis sets for P and Cl atoms. Based on the optimized geometries of complexes 1-4, a counterpoise correction was carried out for the basis-set superposition error (BSSE) of the interaction energies. Nature bond orbital (NBO) and frontier orbital analyses were also performed for all the complexes to study the Ir-Hg interactions and the nature of the redox reactions. Our conclusions are as follows: products of the redox reactions (complexes 2 and 4) are more stable than that of the nonredox reaction (complex 3). The strength of the Ir-Hg interaction increases as follows: 3<4<2. As the strength of the Ir-Hg interaction increases, the difference between the Ir and the Hg contribution to the HOMO gradually decreases. Ir-Hg σbonding and antibonding orbitals all exist in complexes 2 and 4, and can be described as 0.5985sd0.06Hg+0.8012sd2.48Ir for complex 2 and 0.5794sd0.05Hg+0.8151sd2.48Ir for complex 4. However, in complex 3, the Ir-Hg interaction results from nIr→nHg, σIr—P(1)→nHg, and σIr—C(1)→nHg charge transfer interactions.

Key words: DFT, NBO, Ir-Hg interaction, Redox, Stability