Beiträge zur Komplexchemie des Technetiums I : Darstellung und Eigenschaften von Cyanotechnetat (IV)

Cyanotechnetat(IV) was prepared by the dissolution of $^{99}TcO_{2}$ in a solution of alkaline cyanide. For the isolation and the purification of this complex the Tl(I)-salt was used, which crystallizes in a low symmetric lattice. The elementary analysis leads to the formula Tl$_{3}$[TcO(OH) (CN)$_{4}$] resp. Tl$_{3}[Tc(OH)_{3}(CN)_{4}]$, which is in agreement with the molar conductivity, infra-red, visible and ultra-violet spectra. The molar extinction coefficient $\epsilon$880 nm was found tobe (4,44 ± 0,03) · 10$^{4}$ mol$^{-1}$ · l · cm$^{-1}$. The deviation from LAMBERT-BEERS law yields the stability constant K = (1,3 ± 0,6) · 10$^{8}$ mo1$^{-1}$ · l. In presence of oxidizing agents tke complex gets transformed directly to pertechnetatot. Under similar conditions of synthesis rhenium forms the complex ion $[ReO_{2}(CN)_{4}]^{3}$- with a pentavalent central atom. Our results prove the remarkable difference between technetium and rhenium in the stability of the +5 oxidation state