1.2.3.5- Dithiadiazolyls derivatives

In solution, the phenyl derivative 12.29 (R = Ph) is fluxional. The mechanism of the fluxional process has been shown by an N NMR investigation of a partially N-labelled sample, Le., PhCN2 N3S3 ( N = 99% N), to involve a series of 1,3-nitrogen shifts (Section 4.8.4). Thermolysis or photolysis of 12.29 generates the corresponding 1,2,3,5-dithiadiazolyl radicals [RCNaSa]". ... 

Chemistry of dithiadiazolium and dithiadiazolyl rings 95AHC(62)137. Epoxy derivatives of vinyltetrazole 97MI6. 

Figure 3.10 EPR spectra of (a) 1,3,2-dithiazolyl and (b) 1,2,3,5-dithiadiazolyl radicals both absorption and first-derivative spectra are shown.

When R = Bu or a polyfluorinated aryl group (4-XCgF4, X = Br, CN, NO2), the 1,2,3,5-dithiadiazolyl radicals [RCN2S2] exist as monomers, whose magnetic properties are of particular interest. The tert-butyl derivative 5.5 is an unusual example of a liquid that is paramagnetic at room temperature the... 

An extensive study of some 11 para-substituted aryl derivatives, 2+ (R = p-X.C6H4-) has recently been published [93JCS(D)967] and shows that the 2+ ring is reversibly reduced to the dithiadiazolyl radical 2- at potentials in the region +0.56 to 0.68 (versus SCE), depending upon the nature of the substituent X. A second irreversible process is also observed which has been attributed to formation of the dithiadiazolide anion 2". This reduction is irreversible due to reaction with the cation. 

Aryl derivatives of 23 are readily degraded with chlorine to dithiatriazines 94 with the rate being dependent on the aryl substituent. The phenyl derivative of 23 undergoes nucleophilic attack by triphenylphosphine or triphenylarsine and is transformed into the monocyclic eight-membered imino compound 95, which has weak transannular S-S bonds (Scheme 2). Thermolysis and photolysis of compounds 23 affords the corresponding 1,2,3,5-dithiadiazolyl radicals. The trifluoromethyl derivative of 23 (R = Cp3) is astonishingly stable and does not react with bromine, chlorine, sulfuryl chloride, or (Cp3)2NO. To date, no explanation has been found <2003EJI3211>. 

A range of derivatives of 2 was examined as part of a systematic approach by Oakley. Planar derivatives, particularly those bearing functional groups, which favour in-plane interactions and the use of di- and tri-radical derivatives to favour lateral interactions, were successfully employed to generate n-stacked structures. However in all cases the systems were subject to a spin-Peierls or charge-density-wave (CDW) distortion of the structure. This distortion of the regular 71-stack opens up a band gap at the Fermi level [Figure 4(b)] and the conductivities of the pristine materials were poor, i.e. insulators or poor semiconductors. The inherently low conduetivity observed in these 7t-staeked dithiadiazolyl (DTDA) dimers arises in part from the band gap, but also... 

Dimerization can be overcome by strategic substitution. A combination of steric and electronic modifications on the C4 aryl group has led to a small number of derivatives that are monomeric in the soHd state, e.g., dithiadiazolyl radicals 84—86 (Figure 11) and the a phase of radical 82 (2003AGE4782, 2004MOL771, 2010CEJ2741, 201IPRB104450). 

The second-derivative EPR spectrum shown below was recorded for the dithiadiazolyl radical, 5.in. The relative intensities of the multiplets are 1 4 7 7 4 1. Account for the observed pattern. 

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