31P solid state NMR studies of metal selenophosphates containing [P2Se6]4-, [P4Se10]4-, [PSe4]3-, [P2Se7]4-, and [P2Se9]4- ligands

P-31 solid-state nuclear magnetic resonance (NMR) spectra of 12 metal-containing selenophosphates have been examined to distinguish between the [P2Se6](4-), [PSe4](3-), [P4Se10](4-), [P2Se7](4-), and [P2Se6](4-) anions. There is a general correlation between the chemical shifts (CSs) of anions and the presence of a P-P bond. The [P2Se6](4-) and [P4Se10](4-) anions both contain a P-P bond and resonate between 25 and 95 ppm whereas the [PSe4](3-), [P2Se7](4-), and [P2Se9](4-) anions do not contain a P-P bond and resonate between -115 and -30 ppm. The chemical shift anisotropies (CSAs) of compounds containing [PSe4](3-) anions are less than 80 ppm, which is significantly smaller than the CSAs of any of the other anions (range: 135-275 ppm). The smaller CSAs of the [PSe4](3-) anion are likely due to the unique local tetrahedral symmetry of this anion. Spin-lattice relaxation times (T-1) have been determined for the solid compounds and vary between 20 and 3000 s. Unlike the CS, T-1 does not appear to correlate with P-P bonding. P-31 NMR is also shown to be a good method for impurity detection and identification in the solid compounds. The results of this study suggest that P-31 NMR will be a useful tool for anion identification and quantitation in high-temperature melts.