Proximate, “Parallel‐In‐Plane” Preoriented Bis(diazenes) − In‐Plane Delocalized Bis(homoconjugated) 4N/5(6)e Anions

Abstract

Synthetic details are presented for a series of more or less rigid, “parallel‐in‐plane” preoriented bis(diazenes), with N=N/N=N distances (d) of 3.3−2.9 Å and interorbital angles (ψ) of 142−164° (X‐ray crystal structures). DFT calculations (B3LYP/6−31G*) and one‐/two‐electron reduction experiments with the two least preoriented, most “distant” bis(diazenes) (dN=N/N=N ca. 3.3 Å; ψ 142−146°) provide more insight into the structural prerequisites for bis(homoconjugative) in‐plane electron delocalization in 4N/5e radical anions and 4N/6e dianions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

In‐Plane Bishomoaromaticity in Tetranitrogen Dianions: Solid‐State, Solution, and Electronic Structures

“…Bisdiazene 3 (Figure 2 a) is more flexible, and the transannular distances are significantly greater than in 1 ( d N⋅⋅⋅N =3.124 Å, ω =159.3°) 1b,d. Still, the bridgehead methyl groups provide kinetic stabilization, and (Li + ) 2 3 2− was found to be highly persistent 1b.…”

“…The single‐determinant calculations used here provide upper16 boundaries for the electron delocalization as determined by δ ( Ω i , Ω j ) and for the degree of covalent transannular NN bonding. Given the experimentally observed significant shortening of the transannular NN distances in the highly rigid cage of 1 upon reduction, hardly any doubts can remain that the compounds described here, which represent the series of 4 N/6 e dianions,1 contain molecules with four cyclically bonded nitrogen atoms1d in form of the bishomotetrazete dianion substructure (Figure 4).…”

Guest–host interaction in an aza crown analog

“…The planar cyclic tetranitrogen molecule is isoelectronic with the cyclobutadiene. The synthesis of some compounds with planar cyclic ions are reported earlier . Geier et al in a combine experimental and theoretical study revealed the in‐plane bis‐homoaromaticity in tetranitrogen dianions.…”

In‐Plane‐Bishomoaromatizität in Tetrastickstoff‐Dianionen: molekulare und elektronische Strukturen

“…Das Bisdiazen 3 (Abbildung 2 a) ist flexibler und signifikant weniger nahgeordnet als 1 ( d N⋅⋅⋅N =3.124 Å, ω =159.3°) 1b,d. Dennoch erwies sich (Li + ) 2 ‐ 3 2− , kinetisch stabilisiert durch die Brückenkopf‐Methylgruppen, als sehr persistent 1b.…”