99 Tc NMR data for Tc compounds in various oxidation states are summarized.An interest in technetium chemistry is due to its extensive use in nuclear medicine [1]. In the last twenty years, nuclear magnetic resonance (NMR) came into wide use for studying technetium compounds [2]. Measurement of the main parameters of 99 Tc NMR spectra, chemical shift and linewidth, allows monitoring the oxidation state of the element and establishing the composition and structure of various complexes, and observation of the variation of these parameters in time allows studying the kinetics of chemical processes involving technetium compounds. The 99 Tc nuclide is extremely convenient for NMR. The sensitivity of the Tc resonance relative to the proton resonance is 0.275 [2]. Although 99 Tc has a noticeable quadrupole moment Q = 3 0.19(5) 0 10 328 m 2 [3], the effect of the 99 Tc NMR line broadening in solutions, caused by the interaction of the quadrupole moment of the nucleus with the electric field gradient (quadrupole relaxation), is attenuated by a large spin I = 9/2 [4]:

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Technetium(I) tetracarbonyl complexes with diethyldithiocarbamate and methylxanthate ligands [TcL(CO)(4)] (L = S(2)CNEt(2) and S(2)COMe) were prepared. Conditions required for the formation of these complexes were found. The crystal and molecular structure of the xanthate complex was determined by single-crystal X-ray diffraction. [Tc(S(2)CNEt(2))(CO)(4)] undergoes decarbonylation both in solution and in the course of vacuum sublimation with the formation of a dimer [Tc(S(2)CNEt(2))(CO)(3)](2) whose structure was determined by single-crystal X-ray diffraction. In donor solvents, [Tc(S(2)CNEt(2))(CO)(4)] and [Tc(S(2)COMe)(CO)(4)] undergo decarbonylation with the formation of tricarbonyl solvates [TcL(CO)(3)(Sol)]. The crystal structure of the pyridine solvate [Tc(S(2)CNEt(2))(CO)(3)(py)], chosen as an example, was determined by single-crystal X-ray diffraction. The possibility of using bidentate S-donor acidic ligands for tethering the tetracarbonyltechnetium fragment to biomolecules was examined.