Elementary addition-substitution reactions. H�ckel approach for the description of aromatic and antiaromatic arylmethyl cations

Quantum chemical study of alternating N/B and N/C π bonds in (un)charged even‐membered 4n and 4n+2 cyclic systems and their related open systems

“…This approach can be helpful to give a description of the reaction of borazine with (CH 3 ) 2 F + resulting in the ionic complex N 3 B 3 H 6 ‐ ‐ ‐ CH 12. According to ab initio calculations by Miklis et al, as well as our calculations, this ionic complex must be strongly related to C 6 H 6 ‐ ‐ ‐ CH, which is the initial step leading to the end product indicated as σ complex 3, 4. The initial step has been characterized as a η 6 complex in which the methyl cation with its empty p orbital coincides with the D 6 h axis of benzene.…”

“…The development of sophisticated methods of calculation as ab initio at very accurate levels did not change the generalized picture obtained by simple calculation methods. The more sophisticated approach has provided tremendous insight into the fine details of the spectroscopy of excited molecules 2 and the dynamics of simple and even more complex organic systems 3, 4.…”

Calculated geometries of dications of bis odd‐membered π‐ring systems containing a NCN fragment and related π‐systems. An opposite out‐of‐plane rotation of the 4nπ‐ring subsystems

“…The significance of the lowest MO for the stability of charge‐transfer complexes has been recognized with the highly symmetrical C 4 H 4 2− , Li 2 + salt 26; see above. In a recent paper 18 we gave attention to the C 6 H 6 CH 3 + complex as η 6 complex (the binding axis is the sixfold axis of the benzene ring) with an intermolecular distance of about 2.60 Å and an electron density transfer of 0.20 toward CH 3 + as was calculated by Miklis et al 27. In that case the contribution of the lowest MO of benzene is about 90%.…”

“…The σ‐electron contribution for localized CX linkages has been obtained from analytical expressions for distances ( R CX ) and corresponding bond energies ( E CX ) 4, 13, 17, 18, in which for X=CH 3 : A=25.771(5), A′=0.190(2), and B=0.02; for X=NH 2 : A=24.683(8), A′=0.182(2), and B=0.02; for X=OH: A=24.098(1), A′=0.177(7), and B=0.02 with p ∈ ℜ ∣50≤ p ≤100. These equations serve several goals.…”

“…This cation can serve as support for our new concept in the description of the first step in the reaction of simple olefinic compounds with halogens. We consider the formation of a TP which may be stabilized, depending on the choice of the substrate, as the crucial step 4, 13, 18. Just as in the case of the 1,2,4,7‐ anti ‐tetramethyl‐2‐norbornyl cation, the TP is not perfect.…”