The crystal structure of KScP(2)O(7)

Single crystals of KScP(2)O(7), potassium scandium diphosphate, were grown in a borate flux. The title compound crystallizes isotypically with KAlP(2)O(7) in space-group type P2(1)/c, Z = 4. The main building block is an {ScP(2)O(11)}(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 M (III) cation, as do the K—O distances within a series of KM (III)P(2)O(7) compounds (M (III) = Al to Y with ionic radii r = 0.538 to 0.90 Å).