Structural differences between Sr-2(VO)(AsO4)(2) and Ba-2(VO)(PO4)(2)

Two new alkaline earth vanadyl compounds, Sr-2(VO)(AsO4)(2) (I) and Ba-2(VO)(PO4)(2) (II), have been prepared by solid state reactions in closed quartz tubes and characterized by single crystal X-ray diffraction methods. Crystal data: (I): monoclinic, C-2h(6) - I2/a, a = 6.873(2), b = 16.307(4), c = 7.196(2) Angstrom, beta = 115.67(2), Z = 4; (II): monoclinic, C-2(3) - I2/a, a = 9.471(2), b = 5.443(1), c = 15.972(4) Angstrom, beta = 101.651(2), Z = 4. (I) is isotypic to Sr-2(VO)V2O8 and Sr-2(VO)(PO4)(2). (II) shows significant differences to the strontium compounds as well as to Ba-2(VO)(VO4)(2). The differences of the crystal chemistry and the similarity of (II) to Ba-2(VO)(PO4)(2) . H2O are discussed.