BA4MN2AG2O(ASO4)(4), A BARIUM MANGANESE O XIDE-ARSENATE SHOWING NONLINEAR O-AG-O DUMBBELLS

Single crystals of Ba4Mn2Ag2O(AsO4)(4) have been prepared by solid sta te reactions using metallic silver as reactant. X-ray techniques led t o monoclinic symmetry, space group D-2h(2)-P2(1)/m, a = 8.739(2), b = 5.912(1), c = 9.440(2) Angstrom, beta = 115.21(1)degrees, Z = 1. The c rystal structure is characterized by O-Ag-O dumbbells, bond angle = 16 5,3 degrees, containing one oxygen atom not associated with the arsena te groups. Considering these facts Ba4Mn2Ag2O(AsO4)(4) may be seen as an oxide-arsenate or an oxoargentate(I)-arsenate. Assuming the oxidati on state +II for manganese, as confirmed by magnetic measurements, the compound has an oxygen deficite which was accounted for by a split po sition model.