1,2,3-Dithiazolyl and 1,2,35-Dithiadiazolyl Radicals as Spin-Bearing ...

fully reversible. We hypothesized that substitution of the hydrogen atom of III-1 with an
alkyl group would lend itself to an accessible radical anionic oxidation state. Several
routes were attempted, however success was only achieved by substitution with an acetyl
group as is described in this chapter.
3.2 Synthesis
It was discovered that the conjugate base of III-1 was unstable in the presence of
trace amounts of acid resulting in the protonation of the anion to regenerate III-1. As a
consequence, the acetyl chloride that was used had to be dried and carefully purified as
the commercial supplier produced the reagent from acetic anhydride and hydrochloric
acid 2 and it is very difficult to commercially obtain any acyl chloride that is free of acid
impurities. The HCl acid impurities can easily be removed by bubble-degassing the
reagent with argon. The acetyl chloride was further distilled over PCl 5 to ensure the
highest possible quality starting material.
The base used to deprotonate III-1 was
triethylamine which was distilled over P 2 O 5 to ensure that the base was dry prior to use.
The addition of triethylamine to the bright red solution of freshly sublimed III-1 in
dry THF resulted in an immediate colour change to a dark violet colour indicating the
formation of the conjugate base of III-1. In a typical preparation, the reaction mixture
was usually stirred for 10-15 minutes after this addition to ensure that all of the starting
material was reacted. Then the distilled acetyl chloride was added via syringe which
resulted in the formation of a heterogeneous reaction mixture containing a pale solid and
an orange filtrate. After stirring for two hours, the solid was removed by filtration under
argon and dried. The off-white powder was analyzed via 1 H NMR and identified as
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