THE DIFFERENTIAL THERMAL ANALYSIS OF CYANO-TRANSITION METAL COMPLEXES

A variety of cyano and mixed cyano-nitrosyl transition metal complexes have been subjected to differential thermal analysis and to study by a technique termed 'dynamic gas evolution.' Most of the complexes were of Fe in either the +2 or +3 oxidation states, but a few analogous Co, Ni, V, Cr, and Mo compounds were also examined. The hexacyano complexes all decomposed to evolve cyanogen---the Fe (II) and Co (III) complexes at about 600 C and the Fe (III) complexes at about 300 C. This decomposition temperature was associated with the relative ease of reduction of the metal ion, since cyanogen evolution can occur only as the result of a redox reaction. The mixed cyano-nitrosyl complexes consistently decomposed to lose first NO (or other, unidentified gases) and then, at higher temperatures, cyanogen. Evolution of NO implies an initial oxidation and then a reduction as the cyanogen is formed. Weight loss determinations and elemental analysis of the products indicate, but do not demonstrate conclusively, the stoichiometry of the DTA products. (Author)