Diaminopolythiol complexes of technetium and rhenium

Abstract

<p>Interest in technetium chemistry is derived from the fact that it is a recently-discovered element and from the use of the isotope ⁹⁹ᵐTc as a radioactive label in diagnostic nuclear medicine. Rhenium belongs to the same group in the periodic table as technetium, which makes the two elements similar in terms of chemical properties. Diaminopolythiol ligands designed for chelation with technetium and rhenium have been synthesized and characterized. Methods of characterization included ¹H NMR, ¹³C NMR, IR, Raman and mass spectroscopy. Double resonance NMR experiments were carried out for confirmation of the NMR assignments. Single crystal X-ray diffraction was used in cases where suitable crystals could be isolated. The unexpected formation of oxo(2-(1'-methyl-1'-mercaptoethyl)-3-(5"-methyl-5"-mercapto-3"-dehydroazahexyl)-thiazolidinato-N³,N³",S¹', S⁵")technetium(V) (7) was reinvestigated. The complex was prepared previously and was thought to have the technetium atom bound to two nitrogen and three sulfur atoms giving a novel TcO(N2S3)¹ complex. The crystal structure determination of the complex showed that the third sulfur atom was not bound to technetium instead it formed a S-C bond to give a five-membered thiazolidine ring. It was shown in this work that the unexpected thiazolidine ring formation had taken place during the ligand synthesis and before the complex formation. The ligand N10-(thioethanoyl)-2,2,5,5-tetramethy-3,4-dithia-7, 10-diazabicyclo(5.3.0)decane (10), was synthesized in a multi-step procedure. The reaction of (10) with ReO(P(Ph)₃)₂Cl₃ led to the unexpected formation of the novel asymmetric Re(V)ON2S2 complex, oxo(1,1-dimethyl-3-aza-6-amidooctane-1,8-dithiolato)rhenium(V) (11). Complex (11) was characterized by single crystal X-ray diffraction and IR and Raman spectroscopy. Throughout this thesis the nomenclature NXSY, where X and Y are not subscripts, indicate an organic ligand with X nitrogen atoms and Y sulfur atoms.</p>