Gd₂OSe₂

Single crystals of digadolinium monooxy­gen diselenide, Gd₂OSe₂, have been obtained from a KBr flux. The compound is isostructural with the low-pressure form of Dy₂OS₂. All atoms lie on the mirror plane of Pnma. The Gd environments are a GdO₃Se₅ bicapped trigonal prism and a GdOSe₅ distorted octahedron. The two coordination polyhedra pack by face-sharing and edge-sharing to form a [Gd_8/4O_4/4Se^a_8/8-Seⁱ_8/8] fragment, which is the main motif of the structure. These fragments lie in the ac plane and form infinite chains parallel to c through the sharing of Se atoms around atom Gd1. In the a direction, these chains stack through the sharing of an Se atom around atom Gd2, thereby delimiting large pentagonal cavities.