Technetium/ions/salts

E. O. Fischer was the first to prepare arene complexes of technetium. Arene ligands in these compound are typically six-electron donors. The nature of the Tc-arene bond is probably very similar to the one of the Tc-Cp bond. The [Tc(arene)2] complexes (arene = benzene or hexamethylbenzene) are prepared by the reaction of TcCLt with the appropriate arene in the presence of AICI3/AI. In a typical reaction, TcCLt, AICI3, and aluminum were heated with benzene in a sealed tube to 135 °C for two days. The product is precipitated as a salt using the hexafluorophosphate ion. A variety of other 18-electron compounds can be prepared from this material, particularly through chemical reduction. 

In addition to the ReHg- ion there is a technetium analog. Both of these exhibit a single, sharp pmr signal despite the existence of two different proton environments. This has been attributed to a rapid intramolecular site-exchange process, already described (page 44). The ReH ion is obtained by reduction of NaRe04 with an excess of sodium in ethanol the isolation of various pure salts requires careful workup procedures.66 The ReH ion... 

ITiis chapter covers syntheses and properties of pertcchnctic acid, pcrtcchnctic acid salts, oxotechnctatc(Vl), ternary and quaternary oxides of technetium, and the characterization of the TcOr ion. 

The reduced species is cationic, more highly hydrated, and prefers the salt-rich phase. Thus far, the reductant of choice has been SnClj, a common reductant in technetium radiotracer applications. The use of biphase-forming salts that are also chelating agents (e.g., citrate) may stabilize the reduced species and enhance stripping. Stripping into a high-base ABS appears to be hampered by incomplete reduction of technetium or reoxidation to the pertechnetate ion [32]. 

Recently, the preparation and crystal structure of [(C6Hs)3PNP(C6Hs)3]-[TcOCU], a five-coordinate technetium(V) complex have been achieved. The tetrabutylammonium salt, (Bu4N)[TcOCl]4, can be easily prepared and isolated from the reduction of pertechnetate(VII) ion in 12IV hydrochloric acid in nearly quantitative yield. It is soluble in a variety of polar organic solvents and reacts easily with a variety of ligands to form 0x0 technetium(V) complexes. ... 

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