Dispersion interactions with density functional theory: Bonding description of V–NS bond in vanadium–thionitrosyl complex [(nacnac)(OAr)V(NS)]

Dispersion corrected quantum chemical calculations of the complex [(nacnac)(OAr)V(NS)] were investigated at DFT, DFT-D3 and DFT-D3(BJ) level using BP86, PBE, revPBE, PW91 and TPSS functionals. The V–NS bond has essentially multiple bond character. The V–NS bond is relatively stronger than the calculated V–NO bond in the complex [(nacnac)(OAr)V(NO)]. The thionitrosyl ligand is stable in doublet state while [V(nacnac)(OAr)] fragment is stable in quartet state. The V–NS bond dissociation energies considering either doublet or quartet states of the interacting fragments vary in the order 77.2 (revPBE) < 82.1 (BP86) < 87.1 (PW91). The dispersion interaction energy has significant contribution to the V–NS bond dissociation energy. The dispersion corrections with DFT-D3 methods are smaller than the corresponding DFT-D3(BJ). The V–NS bond has a larger covalent character than the ionic character.