Technetium dioxide

The status of Tc(lV) ions in aqueous solution, obtained by dissolution of rc02 aq in diluted HCIO4, was studied by electrophoresis. On the basis of ionic mobilities the existence of the species TcO- and TcO(OH) at pH 1 and pH 2, respectively, was assumed according to the equilibria 

TcO(OH)2 precipitates as TcOt H2O. The pertinent hydrolysis constants were evaluated as 

Anhydrous technetium dioxide, TCO2, can be directly prepared by the thermal decomposition of NH4TCO4 in a nitrogen stream at 700-800 C [21,23]  

like RcO., adopts the molybdenum dioxide structure, a distorted rutile structure type [31] of the space group P2ilc. The approximate cell dimensions of the mono- 

Ilie entire identification, the X-ray structural analysis and the spectromclric characterization of solid TC2O5 and TeOs are still an important challenge to inorganic chemists, all the more as the corresponding rhenium compounds are known to be stable under normal conditions. The dark red ReOi crystallizes in a cubic lattice in the space group Pm3m, forming a prototype [40,41], 

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Technetium metal is obtained by hydrogen reduction of ammonium pertechnetatc. The initial reaction at 200-300 °C produces black technetium dioxide which prevents the loss of ammonium pertechnetatc by sublimation [1], At a temperature of 500-600 °C or, even better, 700-900 °C [2] the metal is left behind as a silver-grey spongy mass according to the reaction ... 

Technetium dioxide trifluoride was recently synthesized by reaction of TC2O7 and XeFh in a 1 3 molar ratio in anhydrous hydrogen fluoride solution via the fluorination... 

Technetium oxide trichloride, TCOCI3, was obtained by reaction of technetium dioxide in a chlorine stream at 30f)-35() °C. The brown, slightly volatile product can be sublimed at about. 500 "C in vacuum. TcOCls shows a strong band in the IR at 1017 cm, which can be attributed to the metal-oxygen stretehing mode. Tlie compound is readily hydrolyzed and disproportionates [.30.98.99] ... 

SrAI204 STRONTIUM DIALUMINIUM TETRAOXIDE 1574 Tc02 TECHNETIUM DIOXIDE 1623... 

M = TcO +,. = 0) of log /CjjQ = —32.3. The minimum solubility was found to be log Kgi2 = -8.24 0.41 that was independent of the chloride concentration used, although there was some scatter in the minimum solubility data of Meyer et al. Eriksen et al. (1992) also studied the solubility of technetium dioxide across the pH range of 6 -12.2. They found a minimum solubility of log = —8.17 0.05,... 

Studies of the base-hydrolysis mechanism for hydrolysis of technetium complexes have further been expanded to an octahedral tris(acetylacetonato)techne-tium(III) [30], Although a large number of studies dealing with base hydrolysis of octahedral metal(III) complexes have been published [31], the mechanism of the tris(acetylacetonato)metal complex is still unclear. The second-order base hydrolysis of the cationic complex tris(acetylacetonato)silicon(IV) takes place by nucleophilic attack of hydroxide ion at carbonyl groups, followed by acetylacetone liberation, and finally silicon dioxide production [32], The kinetic runs were followed spectrophotometrically by the disappearance of the absorbance at 505 nm for Tc(acac)3. The rate law has the following equation ... 

Most chemical properties of technetium are similar to those of rhenium. The metal exhibits several oxidation states, the most stable being the hep-tavalent, Tc +. The metal forms two oxides the black dioxide Tc02 and the heptoxide TC2O7. At ambient temperature in the presence of moisture, a thin layer of dioxide, Tc02, covers the metal surface. The metal burns in fluorine to form two fluorides, the penta- and hexafluorides, TcFs and TcFe. Binary compounds also are obtained with other nonmetaUic elements. It combines with sulfur and carbon at high temperatures forming technetium disulfide and carbide, TcS2 and TcC, respectively. 

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