Improving the Global Electrophilicity Index (GEI) as a Measure of Lewis Acidity

Abstract

The global electrophilicity index (GEI) has been further explored as a general and base-free metric for Lewis acidity. A number of computational methods, including post-Hartree–Fock, density functional theory, and time-dependent density functional theory, have been explored. In this fashion, we sought the method most applicable to a range of different Lewis acids with differing structural and electronic features, including boron trihalides, silicon tetrahalides, fluoroaryl boranes, and group 15 pentahalides. The most accurate and computationally efficient approach was found to use the energies of the orbitals from a geometry optimization at the B3LYP/def2-TZVP level of theory. In addition, the GEI is shown to act as an effective acidity metric that is complementary to the fluoride ion affinity. The GEI also proved to be a better gauge of Lewis acidity for softer bases, as confirmed by comparison to the iodide ion affinity of the group 15 pentahalides.

On the Lewis Basicity of Phosphoramides: A Critical Examination of Their Donor Number through Comparison of Enthalpies of Adduct Formation with SbCl5and BF3

“…Most of the previous calculated values reported in the literature (See Table S1 of the Supporting Information) are close to 500 kJ mol −1 , and therefore close to our LC‐WPBE estimated value. More importantly this estimate is also very close the most accurate (DLPNO‐CCSD(T)/cc‐aug‐pVQZ) calculation reported in the literature, and other very recent estimates using pseudo‐isodesmic schemes . An excellent and very complete compilation on the FIA of SbF 5 was recently reported by Greb …”

“…More importantly this estimate is also very close the most accurate (DLPNO-CCSD(T)/cc-aug-pVQZ) calculation reported in the literature, [37] and other very recent estimates using pseudoisodesmic schemes. [46] An excellent and very complete compilation on the FIA of SbF 5 was recently reported by Greb. [47] Furthermore, the value obtained with the LC-WPBE approach for the FIA of BF 3 (346.7 kJ mol À 1 ) is not far from the two experimental values reported in the literature, [48,49] (331 � 8 and 328.5 � 13.7 kJ mol À 1 , respectively), and in reasonable agreement with a very recent theoretical estimate (353.4 kJ mol À 1 ) based on the use of Global Electrophilicity Index (GEI) as a Measure of Lewis Acidity.…”

First experimental evidence for the elusive tetrahedral cations [EP3]+ (E = S, Se, Te) in the condensed phase

“…We note, that these cations are very strong Lewis acids with FIA values of 775 (S); 803 (Se) and 844 (Te) kJ mol À1 that could be relevant in view of the renewed interest 46 in strong 47 (also cationic 48 ) Lewis acids. 49 They should be compared to classical phosphenium ions [PR 2 ] + with FIA values of 721 (R ¼ NMe 2 ), 789 (R ¼ Mes) and 828 (R ¼ Ph). 50 The easily and in high yield accessible salts ECl 3 [WCA] were tested for their reaction with the known P 3 3À precursor Na[Nb(P 3 )(ODipp) 3 ], related to the synthesis of AsP 3 from AsCl 3 .…”

Nitrenium Salts in Lewis Acid Catalysis

“…TheG utmann-Beckett test and global electrophility index DFT investigations were undertaken to assess the relative Lewis acidity of 1 and 2. [49,50] Both studies revealed them to be weak Lewis acids (see Supporting Information). Undeterred by these results,w ef ocused our efforts on reactivity by studying 1 and 2 in five benchmark catalytic reactions ( Figure 3).…”