Discovery of σ-hole interactions involving ylides

Abstract

The positive electrostatic potentials (σ-hole) have been found in ylides CH2XH3 (X = P, As, Sb) and CH2YH2 (Y = S, Se, Te), on the outer surfaces of group VA and VIA atoms, approximately along the extensions of the C-X and C-Y bonds, respectively. These electrostatic potentials suggest that the above ylides can interact with nucleophiles to form weak, directional noncovalent interactions similar to halogen bonding interactions. MP2 calculations have confirmed the formation of CH2XH3···HM complexes (X = P, As, Sb; M = BeH, ZnH, MgH, Li, Na). The interaction energies, interaction distances, topological properties (electron density and its Laplacian), and energy properties (kinetic electron energy density and potential electron energy density) at the X(1)···H(10) bond critical points are all correlated with the most negative electrostatic potential value of HM, indicating that electrostatic interactions play an important role in these weak X···H interactions. Similar to the halogen bonding interactions, weak interactions involving ylides may be significant in several areas such as organic synthesis, crystal engineering, and design of new materials.

Experimental Charge Density Evidence for Pnicogen Bonding in a Crystal of Ammonium Chloride

“…[11] Like hydrogen bonds, which are sometimes regarded as a special case of s-hole bonding, [10,12] these interactions occur widely from simple inorganic to biological systems [13] and are already used in crystal engineering. [14] Given their importance in crystal structures, [10] s-hole bonds with the elements of groups IV-VII were thoroughly investigated by using computational methods to provide insights into their nature and energetics, including theoretical electrostatic potential [15] and electron density analysis, [16,17] NBO partitioning, [18] and other energy decomposition schemes; [19,20] the applicability of the latter was, however, questioned. [10] This led to rationalization of s-hole bonds as electrostatically driven interactions (with some contribution from polarization and dispersion) [10] that are more frequently found for heavier atoms in a more electron-withdrawing covalent environment, [21] although they still may be observed for the first-row elements ( Figure 1).…”

The competition of Y⋯o and X⋯n halogen bonds to enhance the group V σ-hole interaction in the NCY⋯oPH3⋯NCX and OPH3⋯NCX⋯NCY (X, YF, Cl, and Br) complexes

“…The σ‐hole concept was introduced by Murray et al in 2007 for Group V and Group VI covalently bonded atoms, and it was introduced by Murray et al in 2009 for Group IV covalently bonded atoms . From then on, the σ‐hole concept is increasingly being invoked to interpret noncovalent interactions of Group IV–VI atoms …”

“…[7] From then on, the r-hole concept is increasingly being invoked to interpret noncovalent interactions of Group IV-VI atoms. [8][9][10][11][12][13][14][15] Group IV-VI atoms could process the r-hole, for instance, Murray et al compute the r-hole with a V S,max 5 21.60 kcal/ mol with B3PW91/6-31G(d,p) level on the 0.001 a.u. contour of the molecular electron density of phosphorus oxide trichloride O@PCl 3 , along the extension of OAP bond.…”

Mutual enhancing effects of the σ-hole interactions and halogen/hydrogen-bonded interactions in the iodine-ylide containing complexes

“…In our previous work [27,28], r-holes have been found in ylides CH 2 XH 3 (X = P, As, Sb) and CH 2 YH 2 (Y = S, Se, Te), see Fig. 1, on the outer surfaces of group V and VI atoms, approximately along the extensions of the C-X and C-Y bonds, respectively.…”