Tetramethylammonium Cation: Directionality and Covalency in Its Interactions with Halide Ions

Abstract

The degree of interpenetration of the van der Waals crusts of two atoms, represented by a penetration index, is defined to better quantify the meaning of the nonbonding contact distances between two atoms, which should allow us to compare different atom pairs on the same footing. The structural trends of the intermolecular contacts between the tetramethylammonium cation (TMA) and halogen atoms are reviewed, and a computational study of model X···TMA ion pairs (X = F, Cl, Br, I, Au) is presented. The results disclose two energy minima, in each of which the anion simultaneously interacts with three hydrogen atoms. The bonding mechanisms in the two cases are discussed based on the results of the tools of the trade that provide a consistent picture in which a distribution of charges significantly varies not only around each different atom but is also strongly dependent on the distance to the central N atom. This behavior, together with some non-negligible covalent character of the interionic interaction, is not predicted from a single-molecular electrostatic potential map of the TMA cation.

Electrophilicity of neutral square-planar organosilver(iii) compounds

“…Displacement-ellipsoid diagram (50% probability) of the solvates (CF 3 ) 3 Ag(L)•L' as found in single crystals of 2•NCMe (a), 2•py (b), and 5•OCMe 2(c). The Ag•••L' distance is indicated in each case together with the corresponding penetration index, p(AB) 13. Crystallographic details and relevant structural parameters are given in the ESI †.…”

“…This kind of interaction is best described making use of the descriptor recently introduced by Álvarez and coworkers, namely the penetration index. 13 This descriptor§§The penetration index, p (AB), of two given atoms A and B is defined as follows: p (AB) = 100·[ ν (A) + ν (B) − d (AB)]·[ ν (A) + ν (B) − r (A) − r (B)] −1 , where d (AB) is the actual distance between the involved atoms, and r (A)/ ν (A) and r (B)/ ν (B) are their respective covalent/van der Waals radii. 13 , p (AB), provides a measure of the interpenetration of the electron clouds of the involved atoms A/B and is especially suited for interactions lying between typically covalent and van der Waals bonding interactions, i.e.…”

Anion Binding Based on Hg3 Anticrowns as Multidentate Lewis Acidic Hosts

“…For monoatomic anions, DLPNO-CCSD(T) interaction energies are considerably high and depend on the size of the anion, being maximum for hydride (−96.9 kcal/mol) and minimum for iodide (−48.8 kcal/mol). It is interesting to note that the interaction energies calculated for anions show a nice linear correlation ( R 2 = 0.97) with the degree of penetration between X and Hg atoms 30 (see Figure S1 in the Supporting Information ). On the other hand, for neutral LBs, the strength of the interaction diminishes significantly, ranging from −9.7 kcal/mol for water to −16.0 kcal/mol for acetone.…”

Coordination of E–C Bonds (E = Zn, Mg, Al) and the Zn–H Bonds of (C5Me5)ZnH and (C5Me5)ZnZnH across a Quadruply Bonded Dimolybdenum Dihydride Complex

“…To analyze the bonding parameters of the Mo 2 H triangle and the various Mo 2 –R–E–H rings, with different main group electropositive metals E and where R can be a hydride or an alkyl or aryl group, it is convenient to use the interpenetration indices introduced by one of us recently . In short, a penetration index for an A–B atom pair calibrates the degree of interpenetration of their van der Waals crusts, the portion of space comprised between a sphere with the van der Waals radius and the inner sphere with the covalent radius of an atom.…”

“…21 The direct Zn−Zn bond of the dizincocene reactant is preserved (2.347(4) Å, FSR = 0.96), and the Zn−η 5 various Mo 2 −R−E−H rings, with different main group electropositive metals E and where R can be a hydride or an alkyl or aryl group, it is convenient to use the interpenetration indices introduced by one of us recently. 36 In short, a penetration index for an A−B atom pair calibrates the degree of interpenetration of their van der Waals crusts, the portion of space comprised between a sphere with the van der Waals radius and the inner sphere with the covalent radius of an atom. Thus, a penetration index p AB takes values of around 0% when the two atoms are at around the van der Waals distance (the sum of the van der Waals radii), reach values of around 100% when they are at bonding distance (the sum of their covalent radii), and appear at intermediate values for weak or noncovalent interactions.…”