Pr5Si3N9

Single crystals of Pr5Si3N9, pentapraseodymium trisilicon nonanitride, were obtained by the reaction of elemental praseodymium with silicon diimide in a radio-frequency furnace at 1873 K. The crystal structure consists of a chain-like Si-N substructure of corner-sharing SiN4 tetrahedra. An additional Q(1)-type [SiN4] unit is attached to every second tetrahedron directed alternately in opposite directions. The resulting branched chains interlock with each other, building up a three-dimensional structure. The central atoms of the Q(1)-type [SiN4] unit and of its attached tetrahedron are situated on a mirror plane, as are two of the four crystallographically unique Pr3+ ions. The latter are coordinated by six to ten N atoms, with Pr-N distances similar to those of other rare earth nitridosilicates.