# How do you explain very high vanadyl phosphate NMR chemical shifts?

Generally, phosphates have chemical shifts in the range -20 to 10 ppm. For vanadyl phosphates containing $\ce{V^{4+}}$, the isotropic chemical shift is about 1500 ppm. Why?

$\ce{V^{4+}}$ (and $\ce{V^{3+}}$) is paramagnetic, and therefore you would expect a very large change in chemical shift. Paramagnetic shifts arise from the interaction of the observed nucleus with unpaired electron spin of the paramagnetic metal ion. The observed isotropic shift comes from two interactions: the contact shift and pseudo-contact shift.