Dunkelgrüne Einkristalle von Ba(VO)As2O7 wurden durch Festkörperreaktionen in geschlossenen Quarzampullen dargestellt. Röntgenographische Untersuchungen führten zu monokliner Symmetrie, Raumgruppe C 2h5 P21/a, mit a = 6,843(2), b = 14,636(4), c = 7,460(2) Å, β = 116,02(2)°, Z = 4. Es besteht keine Isotypie zu BaV3O8 (= Ba(VO)V2O7). Die Kristallstruktur zeichnet sich durch  ∞2[(VO)As2O7]‐Schichten parallel zu (110) aus, die durch Ba2+‐Ionen verknüpft werden. As5+ zeigt tetraedrische und V4+ die für Vanadylgruppen typische quadratisch pyramidale Koordination mit einem kurzen VO‐Abstand.

Dark green single crystals of Sr2(VO)P2O8 have been prepared by solid state reactions in closed quartz tubes. X-ray investigations led to monoclinic symmetry, space group C2h6-I2/a, a = 6.744(4), b = 15.866(4), c = 7.032(2) Å, β = 115.41(2), Z = 4. Sr2(VO)P2O8 is isotypic to Sr2(VO)V2O8 and shows V4+ in split positions. The split positions are in non-centric octahedral coordination forming a short vanadium to oxygen distance typical for the vanadyl group. The crystal chemistry of the monovanadyl orthophate Sr2(VO)P2O8 is discussed considering related divanadyl phosphates.

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structure structure (solids and liquids) D 2000 -007Ba(VO)As2O7 -A Vanadyl-Diarsenate with Layered Structure.-Single crystals of the title compound are prepared by annealing pressed pellets of BaAs2O6, V2O5, and V2O3 at 750 • C (evacuated quartz tube, 3 weeks). Ba(VO)As2O7 crystallizes in the monoclinic space group P21/a with Z = 4. The structure is characterized by 2. infin.((VO)As2O7) layers built up by corner-sharing As2O7 double tetrahedra and VO5 pyramids. The Ba2+ ions are located between the layers. The V atoms exhibit one short V-O bond typical of a vanadyl group. -(WADEWITZ, C.; MUELLER-BUSCHBAUM,