Pr5Si3N9

Single crystals of Pr(5)Si(3)N(9), penta-praseodymium trisilicon nona-nitride, were obtained by the reaction of elemental praseo-dymium 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) tetra-hedra. An additional Q(1)-type [SiN(4)] unit is attached to every second tetra-hedron directed alternately in opposite directions. The resulting branched chains inter-lock with each other, building up a three-dimensional structure. The central atoms of the Q(1)-type [SiN(4)] unit and of its attached tetra-hedron 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.