Abstract: 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 CAD_4 diffractometer with MoK_a radiation, The space group is Cmca with a= 1.3938(1), b=1.6350(2), c=1.61 nm, Z=4, D_c=2.588 g/cm~3, μ=38.115 cm~(-1). The positions of all Mo and As atoms were determined by direct method.The others of the non-H atoms were revealed by difference Fourier synthe- sis. 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-C_3H_7As)_2Mo_6O_(24)~(4-), and four caions CN_3H_6~+. In the anion, six distorted octahedra MoO_6 join together to form a six membered ring, which is capped, top and bottom, by the C_3H_7As groups as a cage. The center of anionis 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 betweem the cations and anions throughout the whole crystal. Thus, each anion relates twelve neighbouring ones.