The crystal structure of KScP2O7

Single crystals of KScP2O7, potassium scandium diphosphate, were grown in a borate flux. The title compound crystallizes isotypically with KAlP2O7 in space-group type P21/c, Z = 4. The main building block is an {ScP2O11}9– unit, forming layers parallel to (001). These layers are stacked along [001] via common corners of octa­hedral and tetra­hedral units to span up large hepta­gonal cavities that host the potassium cations with a coordination number of 10. The P—O—P bridging angle increases with increasing size of the octa­hedrally coordinated MIII cation, as do the K—O distances within a series of KMIIIP2O7 compounds (MIII = Al to Y with ionic radii r = 0.538 to 0.90 Å).