Silver trimagnesium phosphate bis-(hydrogenphosphate), AgMg(3)(PO(4))(HPO(4))(2), with an alluaudite-like structure

Abstract

The title compound, AgMg(3)(PO(4))(HPO(4))(2), which has been synthesized by the hydro-thermal method, has an alluaudite-like structure which is formed by edge-sharing MgO(6) octa-hedra (one of which has symmetry 2), resulting in chains linked together by phosphate groups and hydrogen bonds. The three-dimensional framework leads to two different channels along the c axis, one of which is occupied by Ag(+) ions with a square-planar coordination. The Ag(+) ions are disordered over two sites in a 0.89 (3):0.11 (3) ratio. The OH groups, which point into the other type of channel, are involved in strong O-H⋯O hydrogen bonds. The title compound is isotypic with the compounds AM(3)H(2)(XO(4))(HXO(4))(2) (A = Na or Ag, M = Mn, Co or Ni, and X = P or As) of the alluaudite structure type.

Fig. 1.

Partial plot of AgMg3(PO4)(HPO4)2 crystal structure. Displacement ellipsoids are drawn at the 50% probability level. Only the major component of the disordered silver atom is shown. Symmetry codes: (i) -x + 1/2, y - 1/2, -z + 1/2; (ii) x + 1/2, y - 1/2, z + 1; (iii) x + 1/2, -y + 1/2, z + 1/2; (iv) -x + 1/2, -y + 1/2, -z + 1; (v) -x + 1, y, -z + 3/2; (vi) -x + 1, -y, -z + 1; (vii) -x + 1, -y, -z + 2; (viii) x + 1/2, -y + 1/2, z - 1/2; (ix) -x + 1/2, -y + 1/2, -z; (x) -x + 1, y, -z + 1/2; (xi) -x, y, -z + 1/2; (xii) -x + 1/2, y + 1/2, -z + 1/2; (xiii) x - 1/2, y + 1/2, z - 1.

Fig. 2.

A three-dimensional polyhedral view of the crystal structure of the AgMg3(PO4)(HPO4)2, showing the channels running along the c direction,at 0,0,z and 1/2,0,z. Hydrogen bonds are indicated by dashed lines.