Crystal structures of Ag5Cu(AsO4)(As2O7) and Ag7Cu(As2O7)2Cl with a survey on pyroarsenate anions

Abstract

Abstract The crystal structures of two hydrothermally synthesized AgCu-arsenates were determined by single crystal X-ray work: Ag5Cu(AsO4)(As2O7) [a = 5.859(1), b = 9.019(2), c = 10.384(2) Å, α = 97.18(2), β = 90.98(2), γ = 92.11(2)°, space group P[unk], Z = 2, Rw = 0.034 for 5827 observed data and 185 variable parameters] and Ag7Cu(As2O7)2Cl [a = 10.335(2), b = 8.992(2), c = 16.546(3) Å, β = 95.21(2)°, space group Cc, Z = 4, Rw = 0.035 for 3202 observed reflections and 243 variable parameters]. The environment of the Cu atom in Ag7Cu(As2O7)2Cl is peculiar: the Cu–O bond lengths of 1.914(7), 1.945(6), 2.136(8), 2.147(7), 2.250(8), and 2.344(7) Å show an uncommon [2+2+2] coordination (distorted octahedron). The two Cu atoms in Ag5Cu(AsO4)(As2O7) are [4] and [4+2] coordinated, all the Ag atoms are irregularly [5], [6], and [7] coordinated to O (and Cl) atoms. The geometry of the pyroarsenate groups are compared to data from literature.