Silver(I) diaquanickel(II) catena-borodiphosphate(V) hydrate, (Ag0.57Ni0.22)Ni(H2O)2[BP2O8]·0.67H2O

• Main Authors: Hafid Zouihri, Mohamed Saadi, Boujemaa Jaber, Lahcen El Ammari
• Format: Article
• Language: English
• Published: International Union of Crystallography 2011-08-01
• Series: Acta Crystallographica Section E
• Online Access: http://scripts.iucr.org/cgi-bin/paper?S160053681102962X

The structure framework of the title compound, (Ag0.57Ni0.22)Ni(H2O)2[BP2O8]·0.67H2O, is the same as that of its recently published counterpart AgMg(H2O)2[BP2O8]·H2O. In the title structure, the Ag, Ni, B and one O atom are located on special positions (sites symmetry 2). The structure consists of infinite borophosphate helical [BP2O8]3− ribbons, built up from alternate BO4 and PO4 tetrahedra arranged around the 65 screw axes. The vertex-sharing BO4 and PO4 tetrahedra form a spiral ribbon of four-membered rings in which BO4 and PO4 groups alternate. The ribbons are connected through slightly distorted NiO4(H2O)2 octahedra, four O atoms of which belong to the phosphate groups. The resulting three-dimensional framework is characterized by hexagonal channels running along [001]. However, the main difference between the structures of these two compounds lies in the filling ratio of Wyckoff positions 6a and 6b in the tunnels. Indeed, in this work, the refinement of the occupancy rate of sites 6a and 6b shows that the first is occupied by water at 67% and the second is partially occupied by 56.6% of Ag and 21.6% of Ni. In the AgMg(H2O)2[BP2O8]·H2O structure, these two sites are completely occupied by H2O and Ag+, respectively. The title structure is stabilized by O—H...O hydrogen bonds between water molecules and O atoms that are part of the helices.