Intermolecular dihydrogen bonding in VI, VII, and VIII group octahedral metal hydride complexes with water

Abstract

The nature of dihydrogen bonding (DHB) in VI, VII, and VIII group octahedral metal hydride complexes with H2O has been studied systematically using quantum theory of atoms-in-molecule (QTAIM) analysis. A dihydrogen bond (H· · ·H) between hydride ligand and hydrogen of H2O is revealed in QTAIM analysis with the identification of a bond critical point (bcp). The DHB is due to the donation of electron density from the hydride ligand to the hydrogen of H2O. A strong linear correlation is observed between intermolecular H· · ·H distance (dHH) and electron density (ρ) at the bcp. Structural parameters suggested the highly directional nature of DHB.Weak secondary interactions between oxygen of water and other ligands contribute significantly to the binding energy (Eint) of DHB complex (2.5 to 13.2 kcal/mol). Analysis of QTAIM parameters such as kinetic- (Gc), potential- (Vc) and total electron energy density (Hc) revealed the partially covalent character of DHB in majority of the complexes while a few of them showed closed shell character typical of purely non-covalent interactions.