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lsomorphous hexacyanocobaltate( 111) complexes with the bivalent metal cations Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, and Cd2+ have been labelled with 57C0 and used as Mossbauer sources. Whilst the spectrum of the complex Fe3[57Co(CN)6]2 can be resolved into a single line corresponding to the ion Fe1'(CN),4-and a doublet, those of all the other sources result in two doublets, of which one corresponds to the ion Fe111(CN),3-.The extra doublet in these spectra shows that the 57Co-57Fe electron-capture reaction gives rise to the formation of a new 57Fe labelled species, tentatively identified as a pentacyanide ion. The relative yield of the new species decreases with increasing ionization energy for the divalent cation. This can be understood by assuming that the observed chemical effects are due to Auger cascades followed by Coulomb fragmentation; if, however, the charge relaxation is sufficiently rapid, such fragmentation may be prevented.

Mossbauer emission spectra of iron and cobalt complexes, doped or labelled with 57C0, demonstrate that the 57Co(EC)57Fe reaction can have significant chemical effects, although the probability of displacement of the nascents7Fe is very low. Measurements on spe~ifically~~Co-labelled [Co(bipy),] [Co(CN),],2HZO failed to show transfer of b7Fe from one complex to the other.MOSSBAUER emission spectra of 57Fe formed by EC-can release an Auger cascade, Fe3+ may readily be decay of 57C0 in cobalt compounds often contain re-formed from Co2+; further it has been shown that in sonances which are different from those of the corre-hydrated cobaltous compounds Fe3+ can be stabilized sponding iron compounds.l Since the EC-process via radiolysis of water by the Auger electrons. The 1 H. H. Wickman and G. K. Wertheim, in ' Chemical Ap-appearance of resonances corresponding to FeII species plications of Mossbauer Spectroscopy,' eds. V.

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