Technetium tetrachloride

The formation of the hydrides may proceed via bis(jr-cyclopentadienyl)-metal halide complexes, since compounds such as (ir-CeH ReCU+CI-and (t-CjHOjWCU are known and are readily reduced to the neutral hydrides on treatment with lithium aluminum hydride 64) (Eq. 5). Treatment of technetium tetrachloride with sodium cyclopentadiene does not give a hydride analogous to that of rhenium. Molecular weight determina-... 

Kiba et al. propose the separation of technetium from rheniiun by carbon tetrachloride extraction using potassium ethyl xanthate as reducing agent. 

ReO , and Hg, however, only slightly. CrOj forms a similar complex, but the technetium complex can be separated from the chromium complex by extracting the former into carbon tetrachloride. According to Fujinaga et al. the method can be improved by the use of 1 M hydrochloric acid instead of sulfuric acid. 

Microgram amounts of TcOj can be ascertained by measuring the absorbance of the colored complex, formed with toluene-3,4-dithiol in 2.1 M HCl, after extraction into carbon tetrachloride. One hour must be allowed for the development of the color. ITie molar absorbance index at 410 nm is 1.1-10" mole -1-cm. Beer s law is followed over the range of 1.1 to 16.1 pg Tc/ml. Because many cations interfere, an initial separation of technetium is necessary [73]. The same complex was used for the determination of technetium in uranium fission element alloys after separation of Tc by distillation from sulphuric acid [74j. I hc complex formation of technetium, rhenium, and molybdenum with toluene-3,4-dithiol and its analytical application have been studied in detail [71]. 

A method was developed to ascertain technetium in the range of pg/ml by reduction of TcO to Tc(IV) with 1,5-diphcnylcarbohydrazidc and subsequent complexa-tion of Tc(lV) with the reagent. The absorbance was measured at 520 nm after extrae-tion of the complex in carbon tetrachloride. The molar absorbance index was found to be 4.86 lO mole 1 cm [80]. 

N aqueous solution of HCl, H2SO4 or H( I04, from which more than 99 % of technetium could be extracted into carbon tetrachloride at 20 C. The concentration of potassium xanthate was 0.1 M. Perrhenate remained entirely in the aqueous phase, thus separation from technetium could be readily achieved. Instead of carbon tetrachloride. other extractants like chloroform. 1,1,1-trichlorocthane, xylene or isopropyl ether are also suitable [153[. 

Recently, technetium nitride trichloride, TCNCI3, was reported to be synthesized by reaction of TeCU and IN3 in carbon tetrachloride. The black-brown solid of TCNCI3, which still has to be identified completely, dissolves in a solution of Ph4As]Cl in dichloromethane to form [Ph4As][ rcNCl4] [102]. 

Technetium oxide tetrachloride. TcOCU, was separated from the mixture of the oxide chlorides, which are produced upon ehlorination of technetium metal at 300 °C. by trap-to-trap distillation in vacuum in the dark. Pure TcOCU is a purple crystalline solid that forms large crystals and melts at 35 °C. It is stable at room temperature if kept out of the light, but decomposes rapidly to TCOCI3 even at -78 "C, if left in sunlight or artificial fluorescent light. The chlorine produced in the photochemical reaction... 

With potassium ethylxanthate in strong acid solution, technetium in the tetravalent or heptavalent state forms a purple complex which is readily extractable with carbon tetrachloride. Molybdenum behaves similarly (see page 320). 

Procedure. 10 ml of the test solution are treated with about 50 ml of a saturated aqueous solution of potassium ethylxanthate and 50 ml of 2 AT hydrochloric acid. 40 ml of chloroform or carbon tetrachloride are added and the mixture centrifuged. The presence of technetium is indicated by a purple color in the organic layer. 

---