EPR studies of Mo(CN)5NO3-: Magnetic parameters and analysis of the ligand hyperfine structure

Abstract

We have observed the EPR spectrum of the ion Mo(CN)5NO 3- under various conditions and have satisfied ourselves that the given formulation is correct. Our best set of magnetic parameters, for the ion in K3Co(CN)6, is: g∥=1.9736, g⊥=2.0168, A∥(Mo)=163.2 Mc/sec, A⊥=76.4 Mc/sec. We have observed an extensive ligand hyperfine structure at 77°K, which we have assigned to 14N in the nitrosyl and in the equatorial cyanides. We find the 14NO hyperfine tensor to have axial symmetry about the figure axis of the complex, with principal values A∥=3.81 Mc/sec, A⊥=11.30 Mc/sec. We find the C14N hyperfine tensor to have approximate axial symmetry about an axis perpendicular to both the figure axis of the complex and the Mo-C-N bond axis, with principal values A ∥=+6.62 Mc/sec, A⊥=-1 Mc/sec. We thus find the fraction of unpaired electron delocalized onto the nitrogen of each cyanide to be 0.053.