The crystal structure of the title compound was determined by single crystal X-ray diffraction analysis. The intensity data were collected on an Enraf-Nonius CAD4 diffractometer with MoK, radiation The space group is Cmca with a = 13,938(1), b=15.330(2), c =16.173(2) angstrom, v.3685,5 angstrom(3), Z=4.D-c =2.5.88g/cm(3), mu = 38.115cm(-1). The positions of all bto and As atoms were determined by direct method. The others of the non-H atoms were revealed by difference Fourier synthesis,The structure was refined by full-matrix least squares procedure to a final R value of 0.047. The molecule of the title compound consists of anion, (n-C3H7As)(2)Mo5O244- and four cations CNSH+ in the anion, six distorted octahedra MoO6 join together to form a six membered ring, which is capped, top and bottom, by the CaH7As groups as a cage. The center of anion is at a special position of symmetry 2/m. The bond angles of O-Mo-O change regularly with different coordinated O atoms, There are many hydrogen bonds between the cations and anions throughout the whole crystal. Thus, each anion relates twelve neighbouring ones.
