Silver(I) diaqua­magnesium catena-borodiphosphate(V) monohydrate, AgMg(H2O)2[BP2O8]·H2O

The title compound contains infinite one-dimensional [BP(2)O(8)](3-) borophosphate helical ribbons, built up from alternate BO(4) and PO(4) tetra-hedra arranged around the 6(5) screw axes. The vertex-sharing BO(4) and PO(4) tetra-hedra form a spiral ribbon of four-membered rings in which BO(4) and PO(4) groups alternate. The ribbons are connected through slightly distorted MgO(4)(H(2)O)(2) octa-hedra, in which the four O atoms belong to the phosphate groups. The free threads of the helices are occupied by silver ions, which are in an irregular environment surrounded by six O atoms. The central channels of the helices, running along the c axis, are filled with the water mol-ecules. The structure is stabilized by O-H⋯O hydrogen bonds between the water mol-ecules and O atoms that are part of the helices. The crystal structure of the title compound is isotopic with other analogous borophosphates such as A(I)M(II)(H(2)O)(2)[BP(2)O(8)]·H(2)O, where A(I) = Li, Na, K or NH(4) (+) and M(II) = Mg, Mn, Fe, Co, Ni, Cu, Zn or Cd.