An Ab Initio Investigation of the Geometries and Binding Strengths of Tetrel-, Pnictogen-, and Chalcogen-Bonded Complexes of CO2, N2O, and CS2 with Simple Lewis Bases: Some Generalizations

Geometries, equilibrium dissociation energies (D-e), and intermolecular stretching, quadrtic force constants (k(sigma)) are presented for the complexes B center dot center dot center dot CO2, B center dot center dot center dot N2O, and B center dot center dot center dot CS2, where B is one of the following Lewis bases: CO, HCCH, H2S, HCN, H2O, PH3, and NH3. 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 center dot center dot center dot CO2 complexes involves the interaction of the electrophilic region around the C atom of CO2 (as revealed by the molecular electrostatic surface potential (MESP) of CO2) with non-bonding or pi-bonding electron pairs of B. The conclusions for the B center dot center dot center dot N2O series are similar, but with small geometrical distortions that can be rationalized in terms of secondary interactions. The B center dot center dot center dot CS2 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-infinity axis of CS2 (as revealed by the MESP) with the n-pairs or pi-pairs of B. The tetrel, pnictogen, and chalcogen bonds so established in B center dot center dot center dot CO2, B center dot center dot center dot N2O, and B center dot center dot center dot CS2, respectively, are rationalized in terms of some simple, electrostatically based rules previously enunciated for hydrogen-and halogen-bonded complexes, B center dot center dot center dot HX and B center dot center dot center dot XY. It is also shown that the dissociation energy D-e is directly proportional to the force constant k(sigma), with a constant of proportionality identical within experimental error to that found previously for many B center dot center dot center dot HX and B center dot center dot center dot XY complexes.