LAUSR

The nature of dihydrogen bonding (DHB) in VI, VII, and VIII group octahedral metal hydride complexes with $$\hbox {H}_{2}\hbox {O}$$H2O has been studied systematically using quantum theory of atoms-in-molecule (QTAIM) analysis. A dihydrogen bond (H$$\cdots $$⋯H) between hydride ligand and hydrogen of $$\hbox {H}_{2}\hbox {O}$$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 $$\hbox {H}_{2}\hbox {O}$$H2O. A strong linear correlation is observed between intermolecular H$$\cdots $$⋯H distance ($$\hbox {d}_{\mathrm{HH}})$$dHH) and electron density ($$\uprho $$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 ($$\hbox {E}_{\mathrm{int}}$$Eint) of DHB complex (2.5 to 13.2 kcal/mol). Analysis of QTAIM parameters such as kinetic- ($$G_{\mathrm{c}}$$Gc), potential- ($$V_{\mathrm{c}}$$Vc) and total electron energy density ($$H_{\mathrm{c}}$$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.Graphical AbstractSYNOPSIS The nature of dihydrogen bonding in octahedral metal hydride complexes with $$\hbox {H}_{2}\hbox {O}$$H2O has been characterized using QTAIM analysis.