Pseudohalogen compounds of astatine: Synthesis and characterization of At/I/-tricyanomethanide-and At/I/-azide-compounds

Abstract

Reactions of At/⊖/⁺, “At^o.H₂O”, AtCl ⁻₂ and AtBr₂ with the pseudohalogenides tricyanomethanide and azide are described. Information on the compound formation of astatine with C/CN/ ⁻₃ and N ⁻₃ could be obtained on the basis of electromigration investigations under variation of the conditions /composition of the electrolyte, pH, exchange reactions of ligands/. For the reaction: [At/H₂O/C/CN/₃]+C/CN/ ⁻₃ ⇆[At/C/CN/₃/₂]+H₂O at 301 K and u=0.075 mol.l⁻¹ K₂=/675±25/ [1.mol⁻¹] and u^o=−/3.50±0.10/×10⁻⁴ [cm².s⁻¹.V⁻¹]. According to this astatine/I/-tricyanomethanide is classified between AtI ⁻₂ and At/SCN/ ⁻₂ . First investigations in azid-containing systems confirm the formation of astatine/I/-azide-compounds. Their composition is probably At/N₃/ ⁻₂ . There is no dependence of the ion mobility of astatine/I/-azide in the investigated range on azide concentration which is due to its high stability.