Poly[[aqua­tri-μ(3)-hydroxido-(μ(4)-2-phos­phon­ato­ethane­sulfonato)­dierbium(III)] monohydrate]

The crystal structure of the title compound, {[Er(2)(C(2)H(4)O(6)PS)(OH)(3)(H(2)O)]·H(2)O}(n), consists of two Er(3+) ions, one (C(2)H(4)O(6)PS)(3−) ion, three OH(−) ions, and two water mol­ecule. The Er(3+) ions form ErO(8) polyhedra., which are connected by μ- and μ(3)-O atoms. Thus, inorganic Er–O–Er layers of edge- and face-sharing polyhedra are observed. Whereas most often in metal phosphono­sulfonates the organic linker bridges adjacent layers, in the title compound, the (O(3)PC(2)H(4)SO(3))(3−) anion is only connected to one Er–O–Er layer. Short interatomic O⋯O distances [2.898 (8), 2.997 (14) and 2.768 (10) Å] indicate hydrogen bonding between the layers. The noncoordinated water mol­ecules are located between the layers.