Oxygenation of Zinc Dialkyldithiocarbamate Complexes: Isolation, Characterization, and Reactivity of the Stoichiometric Oxygenates

S-oxygenation of dithiocarbamate (DTC) complexes has been implicated in their function as industrial anti-oxidants,
as well as in their use as pesticides and most recently in their cumulative toxicity, but little is known of the species
generated. Several S-oxygenated derivatives of N,N-disubstituted DTCs have been synthesized, characterized by
a variety of methods, and their structure and reactivity examined. Low-temperature reaction of bis(N,N-diethyldithiocarbamato)zinc(II), Zn(deDTC)2 1, with oxygenating reagents (hydrogen peroxide, m-chloroperbenzoic acid,
urea hydrogen peroxide) yields mono-oxygenated DTC complexes (N,N-peroxydiethyldithiocarbamato)(N,N-diethyldithiocarbamato)zin(II), Zn(O-deDTC)(deDTC), 2 and bis(N,N-peroxydiethyldithiocarbamato)zinc(II), Zn(O-deDTC)2, 3. The tetraoxygenated derivative bis(N,N-diethylthiocarbamoylsulfinato)zinc(II), Zn(O2-deDTC)2, 4, was
cleanly obtained by initial reaction of the DTC salts with stoichiometric oxidant prior to complexation with Zn(II).
X-ray crystallographic analysis of 2, 3, and 4 show that the peroxydithiocarbamate ligands are S,O-bound. Similar
derivatives were obtained from the homoleptic dimethyl and pyrollidine DTC Zn complexes. These oxygenated
species display unique 1H and 13C NMR variable-temperature spectra, as the symmetry of DTC ligand is broken
upon oxygenation; total line shape analysis (TLSA) was used to compare the energetic parameters for rotation
about the C−N bond in several derivatives. Compounds 2, 3, and 4 were deoxygenated by alkyl phosphine,
regenerating the parent dithiocarbamate 1. The peroxydithiocarbamate complexes were susceptible to base-catalyzed
hydrolytic decomposition, giving ligand-based products indicative of S-oxidation and S-extrusion.