Adducts of NF 2+ with diatomic and simple polyatomic ligands: a computational investigation on the structure, stability, and thermochemistry

Abstract

The structure, stability, and thermochemistry of all the gaseous NF 2 +(L) adducts which have been experimentally investigated to date by mass spectrometric techniques, including L=HF, HCl, H 2O, CO, CO 2, N 2O, and NF 3, have been computationally studied by high-level of theory ab initio and DFT calculations. The investigation has been also extended to the still unexplored adducts of NF 2 + with H 2S, NH 3, and PH 3. The geometries of all the investigated species have been optimised at the B3LYP/6-31G(d) level of theory, and accurate total energies have been obtained using the G2MS procedure. It has been possible to build up a theoretical scale of difluoronitrenium ion affinity (DFNA) and difluoronitrenium ion basicity (DFNB), defined here as the minus enthalpy and free energy changes, respectively, of the association of NF 2 + to L with formation of the NF 2 +(L) adduct. The calculated values (kcal mol −1) of DFNA, 10.1 (L=HF), 10.7 (L=CO 2), 17.0 kcal mol −1 (L=NF 3), 17.5 (L=N 2O), 20.7 (L=HCl), 25.0 (L=CO), 33.1 (L=H 2O), 57.6 (L=H 2S), 78.0 (L=NH 3), and 84.7 (L=PH 3), demonstrate the occurrence of periodic trends in the stability of the NF 2 +(L) adducts. In addition, reasonably good correlations have been found between the DFNA and the proton affinity (PA) and the DFNB and the gas-phase basicity (GB) of the presently investigated ligands.