On the Bonding of Selenocyanates and Isoselenocyanates and Their Protonated Derivatives

Abstract

The structure, bonding, and protonation of NCSeX and XNCSe (X = Me, F, Cl, Br) derivatives has been investigated at the B3LYP/6-311++G(3df,2p)//B3LYP/6-31+G(d,p) level of theory. Three different approaches, namely, ELF, AIM, and NBO indicate that three main factors are responsible for the enhanced stability of the selenocyanates with respect to the isoselenocyanates when the substituents are halogens, whereas for alkyl substituents, it is the other way around: (a) the Se-X (X = F, Cl, Br) bonds are much stronger than the Se-X (X = Me); (b) the N-X (X = F, Cl, Br) bonds are much weaker than the N-X (X = Me) ones; (c) on going from the selenocyanates to the isoselenocyanates, when the substituents are halogen atoms, there is a significant weakening of the CN bond, which becomes essentially a double bond, whereas upon methyl substitution the CN bond retains its triple bond character. The same stability trends are observed for the corresponding N-protonated species. More importantly, the calculated stability differences are rather similar to those obtained for the neutral compounds, so that selenocyanates and isoselenocyanates exhibit rather similar basicities in the gas phase. Both types of isomers behave as gas-phase nitrogen bases.

Nature of E–E bonds in heavier ditetrel alkyne analogues ArEEAr (Ar = C6H3-2,6(C6H3-2,6-Pri2)2; E = Si, Ge, Sn, and Pb)

“…This conclusion can also be drawn from the electron population of the bond basins. In particular, the positions of the valence basins of V(Sn, Sn) and V(Ge, Ge) are different from the other chemical bonds; [50][51][52][53][54][55][56][57][58] the valence basins do not occupy the central region between the two atoms, but have, in effect, fled that region. Furthermore, it is worth noting that the population of the V(E, E) (E = Ge, Sn) bond basin is about 1e.…”

Modelling peptide–metal dication interactions: formamide–Ca2+ reactions in the gas phase

“…Indeed, ELF may provide useful information on bonding patterns in challenging cases in which other approaches fail to give an unambiguous bonding picture, as it is for instance the case for iminoboranes 51 or selenocyanates. 52 ELF calculations were carried out with the TopMod suite of programs. 53 Figure 1a shows the nanoelectrospray spectrum obtained with an equimolar aqueous mixture of calcium chloride and formamide (10 -3 mol L -1 ).…”

Electrochemical and computational study of the initiation step in the photoinduced electron transfer reaction between sulphur and selenide nucleophiles toward 1‐bromonaphthalene

“…Once all the geometries were computed, the proton affinities (PA) were calculated according to Eqns –, these values give a good approximation to the basicity of the anions under study. Evidently, the larger the value of the PA is, the stronger the basicity of anion A¯ is . The results of calculated PA are summarized in Table S1 (see Supporting Information).…”