| Popis: |
An ESR study of the species [Co(CN)6]4− in irradiated single crystals of K3Co-(CN)6 and in irradiated NaCl and KCl doped with [Co(CN)6]3−, has been made, and the ESR parameters are reported. In addition, the ESR spectra of the same materials enriched to 40 atom % in 13C have been measured and it is shown that there is a large superhyperfine splitting from the carbon atoms of the two axial cyanide ligands; in the KCl lattice A | ( 13 C ) = 30.21 G , A ⊥ ( 13 C ) = 26.65 G , A iso ( 13 C ) = 27.84 G and A aniso ( 13 C ) = 1.19 G . The isotropic 13C interaction is considerably larger than has been observed in other transition metal cyanide complexes and indicates direct overlap of the odd electron dz2 orbital with an sp σ orbital of carbon. This indicates that the axial cyanide ligands are not turned around to form a diisocyanide, [Co(CN)4(NC)2]4−, as has been commonly supposed. The 13C splittings and the small 14N interaction for the two axial ligands ( A | ( 14 N ) = 3.72 G , A ⊥ ( 14 N ) = 2.54 G in KCl) are consistent with an ion [Co(CN)6]4− in which the axial cyanides are twisted moderately to give nonlinear CoCN bonding. |
