Effect of high-energy radiation on a range of metal pentacyanonitrosylferrate(II) and pentacyanonitroferrate(II) salts

Exposure of a range of alkali and alkaline earth pentacyanonitrosylferrate(II) salts to /sup 60/Co ..gamma.. rays at 77/sup 0/K gave electron-capture centers having the unpaired electron largely confined to the nitrosyl ligand, as judged by their ESR spectra. These ESR spectra were almost independent of the salt except that for the hydrated sodium salt which changed reversibly to that exhibited by the other salts on cooling to 4.2/sup 0/K. In all cases, ESR spectra assignable to normal d/sup 7/ iron(I) salts are also obtained, and these were enhanced at the expense of the nitrosyl center on annealing above 77/sup 0/K. At least two d/sup 7/ centers were obtained in most cases. One, having axial symmetry, is assigned the structure Fe(CN)/sub 4/NO/sup 2 -/, formed by loss of the axial cyanide ligand, and the other, having nonaxial symmetry, is assigned the structure Fe(CN)/sub 5/NO/sup 3 -/, with both the axial cyanide and the NO group present but bent slightly off the original axis. The nitroferrate (II) salts gave an electron-excess species having the unpaired electron largely confined to the NO/sub 2/ group, whose ESR spectra closely resembled that of the nitrosyl center. However, these were not converted into d/sup 7/ ferrate(I) salts under any circumstances. The Ag(I) salts also gave Ag(II) centers, whose ESR spectra exhibited hyperfine coupling to four equivalent /sup 14/N nuclei in addition to that to /sup 107/Ag and /sup 109/Ag. These d/sup 9/ ions have their unpaired electrons in a d/sub x/sup 2/--y/sup 2// orbital on silver with considerable delocalization onto four in-plane nitrogen atoms.