Arsenates of Divalent Metals Comprising Arsenic Acid—An Update

Divalent metal oxidoarsenates(V) with compositions M(H 2AsO 4) 2(H 3AsO 4) 2 ( M = Mg, Mn, Co, Ni), M(HAsO 4)(H 3AsO 4)(H 2O) 0.5 ( M = Mn, Cd) and Zn(HAsO 4)(H 3AsO 4) were obtained from solutions containing an excess of arsenic acid. Single crystal X-ray diffraction revealed isotypism of the M(H 2AsO 4) 2(H 3AsO 4) 2 ( M = Mg, Mn, Co, Ni) structures with the known Cu and Zn members of this series whereas M(HAsO 4)(H 3AsO 4)(H 2O) 0.5 ( M = Mn, Cd) and Zn(HAsO 4)(H 3AsO 4) crystallize in novel structure types. The two isotypic M(HAsO 4)(H 3AsO 4)(H 2O) 0.5 ( M = Mn, Cd) structures are closely related with that of Zn(HAsO 4)(H 3AsO 4). Both comprise undulating centrosymmetric [ ∝ 1 MO 4/2O 2/1] chains that share corners with HAsO 4 2 ？ tetrahedra and H 3AsO 4 tetrahedra to build up layers extending along (001). Intermediate water molecules (occupancy 0.5) link adjacent layers in the water-containing compound whereas the linkage in the Zn-compound is mediated by weak hydrogen bonding interactions between the layers. Results of a quantitative comparison between all known structures of the M(H 2 XO 4) 2(H 3 XO 4) 2 ( M = Mg, Mn, Co, Ni, Cu, Zn; X = P, As) series as well as between the two M(HAsO 4)(H 3AsO 4)(H 2O) 0.5 ( M = Mn, Cd) structures are presented. View Full-Tex