NUCLEAR MAGNETIC RESONANCE INVESTIGATIONS OF SOME GROUP V METAL FLUORIDES AND OXYIONS

Abstract

The nuclear magnetic resonances of 51V, 93Nb, 121Sb, 123Sb, and 181Ta in solutions of the pentafluorides of these elements were measured. All of these nuclei have large electric quadrupole moments. In most cases the chemical species observed was identified by spin-multiplet splitting of the metal resonance. In aqueous 48% HF solutions the 181Ta resonance could not be observed; the 121Sb and 123Sb resonances consist of a symmetrical septet, corresponding to the hexafluoride ion; the 93Nb resonance consists of a single exchange narrowed line; and the 5IV resonance consists of a symmetrical quintet, corresponding to the VOF4− ion. In alcohol solution NbF5 disproportionates to form NbF6−, whereas in ether and triethylamine solutions, the complexes NbF5•OEt2 and NbF6•NEt3 are formed. The latter complexes were confirmed by proton resonance measurements. Resonances of 5IV in aqueous solutions of V2O5 and of NH4VO3 as a function of pH show a parallel behavior and reveal the presence of six different oxyions of vanadium. Five of these resonances are assigned to the species, VO43−, VO3−, V2O74− V3O106− and VO2+, on the basis of the resonance line width and the pH range in which the resonance appears.