Preparation and crystal structure of a new layered compound - Dirubidium molybdenyldiarsenate

A new layered dirubidium molybdenyldiarsenate, Rb2MoO2 As2O7, has been isolated. Single-crystal X-ray diffraction shows if crystallizes in the P (1) over bar (No. 2) space group with a = 7.466(3) Angstrom, b = 9.122(3) Angstrom, c = 7.361(3) Angstrom, alpha = 109.98(3)degrees, beta = 85.89(4)degrees, gamma=103.65(4)degrees, Z=2, V=464.0(5) Angstrom(3) R(F)=0.0179 and wR(2)(F-2)=0.0483 for 1810 independent reflections with F> 2 sigma(F), The MoAs2O12,, unit consists of a molybdenum MoO6 octahedron sharing one corner with the diarsenate As2O7 group. The title compound framework is built up from MoAs2O12 units sharing corners. The Rb+ cations are located in the interlayer space. The structure of Rb2MoO2As2O7 is different from that of the analogous compound (NH4)(2)MO2P2O7. Structural relationships with the corresponding diarsenate K2MoO2As2O7 and the diphosphates AMOP(2)O(7), (A = Na, K, Cs; M= Mo, Nb) and MP2O7 (M= Mo, Zr) are discussed. Affiliation with the (2D) WOP2O7 diphosphate structure is shown to exist. (C) 1998 Academic Press.