Vanadium NMR Spectroscopy of Hydroxamido Complexes

The 51V chemical shifts of hydroxamidovanadates and their heterocomplexes appear to be useful as diagnostic tools. Table 7.1 gives the chemical shifts of a number of 

51V Chemical Shifts of Selected Aqueous Hydroxamidovanadate Complexes 

FIGURE 7.1 Partial 51V NMR spectrum of vanadate in the presence of IV-methylhydroxy-lamine showing the VL2 region of the spectrum. The presence of two types of complexes with five observable isomers for each type of complex is revealed. Experimental conditions 3.1 mM total vanadate, 4.1 mM total IV-methylhydroxylamine, 1.0 M KC1, 20 mM HEPES buffer, pH 6.6. 

Heteroligand chelate complexes with N or O coordination by such ligands as imidazole or amino acids have only a small influence on the chemical shifts. For 

FIGURE 7.2 NMR spectrum showing the large influence of coordination of S-containing heteroligands on 51V chemical shifts compared to similar O coordinated ligands in bis(N,N-dimethylhydroxylamine)(heteroligand)vanadium(V) complexes at pH 8.50. Experimental conditions total vanadate, 5.0 mM total Af.AI-di methyl hydroxylamine, 40 mM total cysteine, 90 mM KC1, 1.0 M pH, 8.5. 

---