These polyanions are shown in Fig. . In all these cases except for [P 2 S 6 ] 4-, each phosphorus atom is tetrahedrally coordinated to four sulfur atoms. The polyanions simply differ by the number of shared S atoms between pairs of tetrahedra (no sharing in [PS 4 ] 3-, corner-sharing in [P 2 S 6 ] 2-, and edgesharing in [P 2 S 7 ] -4 ). The [P 2 S 6 ] 4-polyanion can still loosely be visualized as two linked tetrahedra, but with a P-P bond rather than S atoms as the link. In all these thiophosphates, P is in the +5 or +4 oxidation state (Fig. ).