Oxysulfides and oxyselenides in sheets, formed by a rare earth element and a second metal

The preparation and structural features of compounds of the general formula(RO)n(MxXy), withR =rare earth, M =IB, IIIA, IVA, or VA elements, andX =S or Se, are described. Four families of oxysulfides can be prepared by the reaction of a rare earth oxysulfide and a post-transition metal sulfide. These include(RO)4Ga2S5forR =Ce(tetragonal P4/mmm) andR =Pr to Sm(orthorhombicPbca of the type (NdO)4Ga2S5);(RO)4Ca1.33S4forR =La and Ce(tetragonal P4/mmm);(RO)4Ge1.5S5forR =La to Nd(orthorhombicPbca type (NdO)4Ga2S5);(RO)4Sn2S6forR =La to Nd(orthorhombicpbnm type (LaO)4Sn2S6). The reaction of lanthanum oxyselenide and the metal selenide gives (LaO)GaSe2, (LaO)InSe2, (LaO)4Ge1.5Se5, (LaO)4Sn2Se6, and (LaO)SbSe2. Crystal data are given for these systems. Although these compounds crystallize in several different space groups, they all have sheet structures formed by alternation of an oxide sheet (RO) and a sulfide or selenide sheet (MxXy). They belong to 7 new structural types. The (RO) sheets have the same tetragonal or pseudotetragonal array ofR4O tetrahedra, but the (MxXy) sheets have various structures, with 2, 3, or 4 layers ofX atoms. The structural characters of these compounds are discussed.