New , -arsenates - the framework structures of Ag(HAsO) ( = Al, Ga) and GaAsO ( = Na, Ag).

The crystal structures of hydro-thermally synthesized silver(I) aluminium bis-[hydrogen arsenate(V)], AgAl(HAsO), silver(I) gallium bis-[hydrogen arsenate(V)], AgGa(HAsO), silver gallium diarsenate(V), AgGaAsO, and sodium gallium diarsenate(V), NaGaAsO, were determined from single-crystal X-ray diffraction data collected at room temperature. The first two compounds are representatives of the MCV-3 structure type known for KSc(HAsO), which is characterized by a three-dimensional anionic framework of corner-sharing alternating O octa-hedra ( = Al, Ga) and singly protonated AsO tetra-hedra. Inter-secting channels parallel to [101] and [110] host the Ag cations, which are positionally disordered in the Ga compound, but not in the Al compound. The hydrogen bonds are relatively strong, with O⋯O donor-acceptor distances of 2.6262 (17) and 2.6240 (19) Å for the Al and Ga compounds, respectively. The two diarsenate compounds are representatives of the NaAlAsO structure type, characterized by an anionic framework topology built of O octa-hedra ( = Al, Ga) sharing corners with diarsenate groups, and cations ( = Ag) hosted in the voids of the framework. Both structures are characterized by a staggered conformation of the AsO groups.