Electronic structure and bonding of the dinuclear metal M2(CO)10 decacarbonyls: applications of natural orbitals for chemical valence

Overlap properties of chemical bonds in generic systems including unusual bonding situations

Chemical bond is a ubiquitous and fundamental concept in chemistry, in which the overlap plays a defining role. By using a new approach based on localized molecular orbitals, the overlap properties, e.g., polarizability [Formula: see text], population p_OP, intra [Formula: see text], and inter [Formula: see text] repulsions, and density ρ_OP, of polyatomic systems were calculated, analyzed, and correlated. Several trends are shown for these properties, which are rationalized by the balance of some well-known effects, such as, electron donor/withdrawing character and electronegativity. The overlap properties of unusual bonds are also analyzed, revealing an OZn₄(OOCH)₆ structure with four equivalent Zn-O chemical bonds with overlap properties like the O-O bond in H₂O₂, while in protonated methane [Formula: see text], it is observed that a CH₃⋯[Formula: see text] bond pattern at the equilibrium structure changes to a [Formula: see text]⋯H₂ pattern upon dissociation. Charge-shift resonance energies, atom-in-molecule properties, and the lone-pair-bond-weakening effects are related to the overlap properties, which can provide alternative views and insights into chemical bonds. Graphical abstract A chemical bond analysis approach based on its overlap properties is presented for the first time. The model was applied directly to 25 diatomics and for 28 bonds in polytomics employing localized molecular orbitals. Correlations of the overlap properties with the charge-shift resonance energies and with atom-in-molecule (AIM) properties were uncovered. In addition, it provided insights into the Zn-O bonds in the unusual OZn₄(OOCH)₆ system as well as in the bonding patterns of [Formula: see text] at equilibrium and upon dissociation.