Abstract
The title compound alpha-ammonium iron(III) bis[hydrogen arsenate(V)], alpha-NH4Fe(HAsO4)(2) (or poly[ammonium bis(thydrogen arsenato)ferrate(III)1, {NH4[Fe(HAsO4)2]}(n)), synthesized hydrothermally, is isostructural with NH4Fe(HPO4)(2). Condensation of the hydrogen arsenate groups with FeO6 coordination octahedra via common corners results in an overall three-dimensional framework containing interconnected channels parallel to the a-, b-and c-axis directions. The NH4+ cations are located in three intersecting tunnels, which is promising as an ion exchange. Hydrogen bonding of the types O-H center dot center dot center dot O and N-H center dot center dot center dot-O consolidates the packing of the structure. The distortion of the coordination polyhedra is analyzed by means of the effective coordination number and distortion indices. Structural relationships with other compounds of general formula (MMTTT)-M-T m[HxO(4))12,(X = P, As) are discussed.