STRUCTURE OF MONOVANADATES IN AQUEOUS-SOLUTION

Using the ammonium salt of the dimeric coordination compound of 2-ethyl-2-hydroxybutanoic acid and vanadate(V) with known crystal structure as a reference, the structures of analogous compounds in aqueous solutions have been deduced by means of H-1, C-13 and V-51 NMR. In these cases vanadate(V) is five-coordinate. Through an analysis of literature equilibrium data for the system dihydrogen vanadate(V) plus 1,2-ethanediol, giving a dimeric vanadate of presumed six-coordinate structure, the precise reaction scheme was established. This scheme is only consistent with a five-coordinate dihydrogen vanadate(V) ion having the composition H4VO5-. The UV-VIS and MCD spectra of this ion are almost identical to those of the five-coordinate reference structure mentioned above.