Pr(5)Si(3)N(9)

Single crystals of Pr(5)Si(3)N(9), 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 SiN(4) tetra­hedra. An additional Q (1)-type [SiN(4)] 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 [SiN(4)] unit and of its attached tetra­hedron are situated on a mirror plane, as are two of the four crystallographically unique Pr(3+) ions. The latter are coordinated by six to ten N atoms, with Pr—N distances similar to those of other rare earth nitridosilicates.