Basic Coordination Chemistry of Technetium

Abstract

The coordination chemistry of technetium in the oxidation states from + 7 to -1 is exemplified. Coordination geometries, magnetic properties and difTerent cores of complex Compounds are reviewed. Stability and reactivity of some analogous complexes of technetium and rhenium are compared.

An investigation of groundwater organics, soil minerals, and activated carbon on the complexation, adsorption, and separation of technetium-99

“…Such a complexation reaction is thermodynamically possible based on the coordination chemistry of technetium (Schwochau and Pleger 1993 Zhang et al, 1995). Our experiments (Fig, 1.12) also indicate Tc04-may form complexes with salicylate.…”

Prediction of uranium and technetium sorption during titration of contaminated acidic groundwater

“…Electrostatics favor SO 4 2− , UO 2 (CO 3 ) 2 2− , and UO 2 (CO 3 ) 3 4− sorption over TcO 4 − in ion exchange reactions. However, this investigation reveals extremely high affinity for TcO 4 − sorption on Al and Fe hydroxides, which is perhaps supported by the fact that TcO 4 − is a large, poorly hydrated anion and has a natural tendency to be strongly sorbed by a variety of adsorbents [8,10,18]. …”

“…Technetium exhibits two primary oxidation states in groundwater-Tc(VII) and Tc(IV) [7]. The Tc(VII) pertechnetate ion (TcO 4 − ) is most stable under oxidizing conditions [8]. Therefore, under oxic conditions, uranium and technetium are anticipated to be present in groundwater as the uranyl (UO 2 2+ ) and pertechnetate (TcO 4 − ) ions [9].…”

Technetium

“…The dimer [Tc(r|-Cp) 2 ] 2 is produced by reduction o f (21) with potassium naphthalide, or by thermolysis o f (22), which produces the hydride [TcH(r|-Cp) 2 ] as a side product (Scheme 9). 95 The x-ray structures o f compounds (21) and (22) which is expected based on analogy to rhenium chemistry. 101 The characterization (including an x-ray structure determination) o f (26) as a polymer has caused some controversy, because o f the "supershort" Tc-Tc bond length o f 0.1867(4) nm (compare with 0.241 n m for (24) and because the spectroscopic data (IR, NMR) reported for (26) (26).…”

“…As indicated in Scheme 9, technetium tetrachloride reacts with KCp to f o r m the sandwich complex [TcCl(rj-Cp) 2 ] (21) and with an excess o f KCp to form the tris(cyclopentadienyl) complex [Tc-(r|-Cp) 2 (r| 1 -Cp)] (22). These two compounds are related in the sense that KCp converts the chloride (21) to the tris(Cp) (22) and H C 1 / N H 4 C 1 converts (22) to (21). The dimer [Tc(r|-Cp) 2 ] 2 is produced by reduction o f (21) with potassium naphthalide, or by thermolysis o f (22), which produces the hydride [TcH(r|-Cp) 2 ] as a side product (Scheme 9).…”