ESR study of the reaction of trithiazyl trichloride with primary aromatic amines

Abstract

Benzenamines (1) react with 1,3,5-tri~hloro-l1~,3L~,51'-1,3,5,2,4,6-trithiatriazine (2) to form the novel radicals 2~21'-2,4,-dithia-1,3-diaza-Zchloro-l,3-butadien-l-yl)-214-2,1,3-benzothiadiazol-l-yls (4) or 2-(5-chlora-21'-2,4-dithia-l,~iaza-1,2-pentadien-l-yl)-214-2,l,~be~ot~adiazol-l-yls ( 4 ' ) . ESR hyperfine splitting constants of 20 different radicals of type 4 are presented, and the mechanism of their formation and the suggested structure of 4 are discussed.

Structures and EPR spectra of binary sulfur–nitrogen radicals from DFT calculations

“…The second published spectrum assigned to this radical has aN = 1.12 mT, but with much narrower lines which also allowed for observation of 33 S coupling of ~0.5 mT at high gain [4]. However, due to the extremely low natural abundance of 33 Figure 3 shows simulations, using hfc values from our calculations, which predict the appearance of the spectra of this radical at natural abundances of the isotopes and with 33 S enrichment.…”

“…In all of these measurements, the two equivalent 14 N nuclei display aN ~0.50 -0.52 mT, in reasonable agreement with our calculated value of 0.40 mT (note that for the heterocycle, assignment to the very similar spectra of dithiadiazolyl free radicals -vide infra -cannot be ruled out). On the other hand, the reported 33 S hfc for the unique sulfur atom of 0.45 mT is in strong disagreement with the significantly larger calculated value of 3.08 mT [4]. As illustrated in Figure 4, the identity of this radical could be confirmed by measurement of the EPR spectrum of a 33 S-enriched sample.…”

“…, while the other appears to be an I = 1 quintet (a ~ 0.63 mT) of I = 1 triplets (a ~ 0.20 mT), albeit from a spectrum of poor signal-to-noise ratio. A much better spectrum obtained during reactions of various amines with S3N3Cl3 at low temperature, which may be related to this second species, has since been published (a = 0.735 and 0.175 mT) [4]. Obviously, neither of these spectra are attributable to [NS] • .…”

“…There are two reports of EPR spectra that may belong to [SNS] • [4,26]. The first is an I = 1 triplet with aN = 1.13 mT obtained from a mixture of radicals produced as decomposition products during the room-temperature cathodic reduction of [S4N5] -(at low temperature the dianion radical [S4N5] -2• is obtained, vide infra) [26].…”

“…In addition, reliable assignments have not been made for the EPR spectra of several S,N species reported as recently as 1990 [4].…”