An Ab Initio Investigation of the Geometries and Binding Strengths of Tetrel-, Pnictogen-, and Chalcogen-Bonded Complexes of CO ₂, N ₂O, and CS ₂ with Simple Lewis Bases: Some Generalizations

Abstract

Geometries, equilibrium dissociation energies ( D _e), and intermolecular stretching, quadratic force constants ( k _σ) are presented for the complexes B⋯CO ₂, B⋯N ₂O, and B⋯CS ₂, where B is one of the following Lewis bases: CO, HCCH, H ₂S, HCN, H ₂O, PH ₃, and NH ₃. The geometries and force constants were calculated at the CCSD(T)/aug-cc-pVTZ level of theory, while generation of D _e employed the CCSD(T)/CBS complete basis-set extrapolation. The non-covalent, intermolecular bond in the B⋯CO ₂ complexes involves the interaction of the electrophilic region around the C atom of CO ₂ (as revealed by the molecular electrostatic surface potential (MESP) of CO ₂) with non-bonding or π-bonding electron pairs of B. The conclusions for the B⋯N ₂O series are similar, but with small geometrical distortions that can be rationalized in terms of secondary interactions. The B⋯CS ₂ series exhibits a different type of geometry that can be interpreted in terms of the interaction of the electrophilic region near one of the S atoms and centered on the C _∞ axis of CS ₂ (as revealed by the MESP) with the n-pairs or π-pairs of B. The tetrel, pnictogen, and chalcogen bonds so established in B⋯CO ₂, B⋯N ₂O, and B⋯CS ₂, respectively, are rationalized in terms of some simple, electrostatically based rules previously enunciated for hydrogen- and halogen-bonded complexes, B⋯HX and B⋯XY. It is also shown that the dissociation energy D _e is directly proportional to the force constant k _σ, with a constant of proportionality identical within experimental error to that found previously for many B⋯HX and B⋯XY complexes.