Technetium cyanide chemistry: synthesis and characterization of technetium(III) and -(V) cyanide complexes

Abstract

Several new technetium cyanide complexes have been prepared and characterized. The reaction of ammonium hexaiodotechnetate(IV) with potassium cyanide in refluxing aqueous methanol under nitrogen yields potassium heptacyanotechnetate(III) dihydrate, K/sub 4/Tc(CN)/sub 7/.2H/sub 2/O (1). Infrared and Raman measurements indicate that 1 has a pentagonal bipyramidal structure (D/sub 5h/) in both solid and solution. Aqueous solutions of 1 are air sensitive, decomposing to potassium oxopentacyanotechnetate(V) tetrahydrate, K/sub 2/TcO(CN)/sub 5/.4H/sub 2/O (2). This species can also be prepared from the reaction of TcO/sub 2/.xH/sub 2/O with hot aqueous potassium cyanide solutions. Hydrolysis of 2 in water yields potassium trans-dioxo-tetracyanotechnetate(V), K/sub 3/TcO/sub 2/(CN)/sub 4/ (3). Preparation of 3 can also be achieved from the treatment of (TcO/sub 2/(Py)/sub 4/)ClO/sub 4/.2H/sub 2/O with aqueous potassium cyanide. Infrared and Raman measurements on 3 are consistent with the proposed trans-dioxo (D/sub 4h/) structure. Reaction of the oxotetrachlorotechnetate(V) anion, TcOCl/sub 4/, with potassium cyanide in methanol produces trans-oxomethoxytetracyanotechnetate(V). (TcO(OMe)(CN)/sub 4/) (4). The full details of the synthesis and characterization of these interesting technetium(III) and -(V) complexes, as well as observations on the infrared and Raman spectra of trans-dioxo metal complexes and the hydrolysis of species 2, are presented.