Energy decomposition analysis of the metal–oxime bond in [M{RC(NOH)C(NO)R}2] (M = Ni(II), Pd(II), Pt(II), R = CH3, H, F, Cl, Br, Ph, CF3)

Quantum chemical calculations using gradient-corrected DFT at the BP86/TZ2P+ level were carried out for the metal–dioxime complexes [M{RC(NOH)C(NO)R}2]with M = Ni, Pd, Pt, R = CH3, H, F, Cl, Br, Ph, CF3. The nature of the metal–ligand bond was investigated with an energy decomposition analysis (EDA). The complexes with electron donating substituents R = H, CH3 have the strongest metal–ligand interaction energies ΔEint, as well as the largest bond dissociation energies. The analysis of the bonding situation revealed that the metal ← ligand σ donation is much stronger than the metal → ligand π backdonation. The breakdown of the orbital interactions into the contributions of orbitals with different symmetry indicates that the donation from the in-plane lone-pair donor-orbitals of nitrogen into the dxy AO of the metal provides about one half of the stabilization which comes from ΔEorb. Inspection of the EDA data indicates that the electrostatic term ΔEelstat is more important for the trend of the metal-oxime interactions in [M{RC(NOH)C(NO)R}2] than the orbital term ΔEorb.