Low Valent Technetium Nitrosyl Complexes

Abstract

<p> This thesis describes reactions involving low valent technetium nitrosyl complexes. O-Substituted hydroxylamines were reacted with [TcOCl4]- in methanol producing [Tc(NO)Cl4]-. NMR studies have shown that two species are present besides the starting material during this reaction. One of these species was confirmed by NMR to be the corresponding alcohol of the O-substituted hydroxylamine. The other species is believed to be a hydroxylamine intermediate that is in equilibrium with the final product, [Tc(NO)Cl4]-. A plausible mechanism for this reaction was proposed that included an oxo group attack of the α-carbon of the O-substituted hydroxylamine which would lead to the formation of the corresponding alcohol. In an attempt to confirm the mechanism, O-18 labeled [TcOCl4]- was synthesized, however, there is no conclusive evidence that the label is transferred to the corresponding alcohol at the present time. Substitution reactions of [Tc(NO)Cl4]- with phenanthroline and bipyridyl ligands were also investigated. Reactions with these ligands produced [Tc^(II)(NO)Cl3phen] (4a) and [Tc^(II)(NO)Cl3bipy] (5), respectively. The crystal structures of these complexes showed that the meridonial isomer is produced with one nitrogen atom of the bidentate ligand trans to the nitrosyl moiety. EPR spectra of these compounds confirm the Tc(II) oxidation state of the metal. All of the chloride ligands of 4a and 5 can be displaced using AgBF4 in acetonitrile solvent, which, in the case of bipyridyl, produces [Tc^(I)(NO)(bipy)2(MeCN)]2+ (6). Other technetium nitrosyl containing complexes are formed in these reactions and are currently awaiting x-ray structure determination.</p>