Strontium manganese diselenite,SrMn(SeO3)2, containing unusual MnO5+1 polyhedra

Hydro­thermally prepared SrMn(SeO₃)₂ contains infinite chains of vertex‐sharing irregular MnO₅₊₁ polyhedra mean Mn—O 2.226 (3) Å], which are fused into layers via pyramidal SeO₃ groups mean Se—O 1.698 (3) Å]. Nine‐coordinate Sr²⁺ cations mean Sr—O 2.715 (4) Å] complete the layered structure.