Neue Sesquisulfide der Lanthanoide im U2S3-typ: Tb2Si3 und Dy2S3

New sesquisulfides o f the lanthanides with the U 2 S3-type structure (M 2 S3, M = T b and Dy) were prepared through the oxidation o f T bC lH 0 67 and D yCl2, respectively, with appropriate am ounts o f sulfur in the presence o f N aCl fluxes in silica protected sealed tan talum containers at 850 C for at least seven days. The preparation from the elements (2M + 3S; M = Tb and Dy) under otherwise analogous reaction conditions and tem peratures was also successful when equim oiar fluxes o f NaCl were applied. The crystal structure was determ ined from single crystal da ta for Tb-,S3 and Dy2 S3, both crystallizing with the U-,S3-type structure (orthorhom bic, Pnm a, Z = 4; T b 2 S3: a = 1067.87(8), b = 388.06(4), c = 1049.07(7) pm; Dy 2 S3: a = 1062.45(7), b = 386.59(4), c = 1044.36(8) pm) when prepared under the above-m entioned conditions.