Methyl Cation Affinities of Neutral and Anionic Maingroup-Element Hydrides: Trends Across the Periodic Table and Correlation with Proton Affinities

We have computed the methyl cation affinities in the gas phase of archetypal anionic and neutral bases across the periodic table using ZORA-relativistic density functional theory (DFT) at BP86/QZ4P//BP86/TZ2P. The main purpose of this work is to provide the methyl cation affinities (and corresponding entropies) at 298 K of all anionic (XH_<i>n</i>−1⁻) and neutral bases (XH_<i>n</i>) constituted by maingroup-element hydrides of groups 14−17 and the noble gases (i.e., group 18) along the periods 2−6. The cation affinity of the bases decreases from H⁺ to CH₃⁺. To understand this trend, we have carried out quantitative bond energy decomposition analyses (EDA). Quantitative correlations are established between the MCA and PA values.