5,5′-bi(1,3,2,4-dithiadiazolylium)(2+) bis[hexafluoroarsenate(V)]: a general synthetic strategy to molecules and radicals containing thiazyl rings

Abstract

The salt [SNS][AsF6] undergoes a quantitative multiple cycloaddition reaction with cyanogen to give the planar, centrosymmetric dication ([graphic omitted])22+, which has been characterised by vibrational and 13C NMR spectroscopy, chemical analysis and X-ray crystallography. While the reaction between cyanogen and SNS+ must proceed via a 1 : 1 cycloadduct, NC[graphic omitted]+, this was not prepared or observed. The cycloaddition of SNS+ to NC[graphic omitted]+ must therefore be kinetically preferred, contrary to arguments based on simple frontier molecular orbital (FMO) theory. By contrast, the reaction of [SNS][AsF6] with [NC[graphic omitted]CH][AsF6] to give [H [graphic omitted]]–[graphic omitted]][AsF6]2 was complete only after 10 weeks at 50 °C, in complete accord with FMO theory. These results are rationalised in terms of the influence of high-energy, in-plane molecular orbitals and the electrostatic interaction between SNS+ and the slightly negatively charged nitrogen atom (N) in the [graphic omitted]+ ring, which facilitates the second cycloaddition. The salt [([graphic omitted])2][AsF6]2 potentially provides access to a new family of eight other bicyclic CNS dications, radical cations and diradicals, of which .[graphic omitted]–[graphic omitted]+, +[graphic omitted]–[graphic omitted]˙ and +[graphic omitted]–[graphic omitted]+ are reported.