Imido complexes technetium

The Tc complex [TcI(N—Ar)s] (28) (see Section 5.2.2.1.2) can be reduced with Na° in THE to yield the green, nonbridged, dinuclear compound [Tc2(NAr)6] (46), in which three imido-ligands are bound to the Tc center and connected by a single bond to the second technetium. The molecule has a staggered, ethane-like structure and is diamagnetic. Reduction of (28) yields another homoleptic imido-complex of Tc, the imido-bridged, tetrahedral, dinuclear compound [Tc2(/u-NAr )2(NAr )4] (47) (Ar = 2,6-diisopropylphenyl). The conformation could be confirmed by X-ray structure analysis the assumption of a Tc Tc bond is confirmed by the... 

Little related work on the technetium analog has been completed. Much of the synthetic work with high-valent Tc has centered on imido complexes,54 or on complexes for use in radiopharmaceuticals.55 Methyl technetium trioxide has been prepared.8 This species is thermodynamically a powerful enough oxidant to cycloadd to alkenes cyclohexene gave (after hydrolysis) c/s-l,2-cyclohexanediol. No chemistry with H202 has been reported it is expected to behave in a similar manner to MTO, unless the change in the metal-oxo bond strength perturbs the overall thermodynamics. 

Scheme 21. Synthesis of mixed imido-aikyi complexes of high valency technetium.

Dianionic organoimido ligands (RN ) are isoelectronic with the oxo group, but complexes of technetium-containing imido ligands are comparatively rare. Although not yet employed in... 

By far, the largest number of structurally characterized rhenium complexes contain the metal in the oxidation state +5 . This can be attributed to the high stability of the rhenium(V) oxo, nitrido, and imido cores with a great variety of ligand systems, but is doubtlessly also related to the fact that rhenium complexes are frequently used as nonradioactive model compounds for the development of technetium radiopharmaceuticals. The dominance of 0 , and NR ligands can be... 

Though hexavalcnt technetium is known to be highly sensitive to oxydation and disproportionation, for instance in the case of tetraoxotcchnetale(Vl) [30, numerous complex compounds of rc(VI) were synthesized and identified and proved to be rather stable under normal conditions. Imido and predominantly nitrido ligands frequently act in mono- and dinuclear complexes as strong stabilizing Tr-clcctron donors [31]. In fluoro complexes the coordination numbers 7 and 8 are verified. In addition catccholato and thiolato ligands form well defined compounds. EPR spectroscopy was shown to be an efficient tool to characterize the complexes. 

Prior to 1980, dithiocarbamate complexes of technetium were unknown. However, over the past 20 years considerable developments have been made, driven mainly by the application of technetium(V) nitride complexes in radiopharmaceuticals. More recently, dithiocarbamate chemistry of technetimn has been more fully explored with diphosphine, carbonyl, oxo, imido, and other ligand combinations. 

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