X-RAY CRYSTAL-STRUCTURE OF GUANIDINIUM HEXAMOLYBDOBIS(ORTHO-NITROPHENYLARSONATE)MONOHYDRATE, (CN3H6)5[(ORTHO-NO2C6H4AS)2MO6O25H].H2O

The structure of guanidinium hexamolybdobis(o-nitrophenylarsonate)monohydrate was determined by single-crystal X-ray diffraction analysis. Each molecule contains one [(o-NO2C6H4As)2Mo6O25H]5- anion, five CN3H6+ cations and one water molecule. The structure of the anion is similar to [(C6H5As)2Mo6O25H]5-, [(C6H5As)2W6O25H]5- and [(p-NH3C6H4As)2W6O25]4- except for one molybdenum atom which is considered as five-coordinated. Five MoO6 octahedra and one MoO5 square-pyramid are connected with edge- or corner-sharings to form a ring. Two o-nitrophenylarsenic groups join the ring above and below. Although the two arsenic atoms are not equivalent in their bonding manner, both dihedral angles between the phenyl plane and the corresponding nitro plane are 28.8°. It may be noted that the two phenyl planes are almost perpendicular to each other. It is indicated that a special oxygen atom may be bonded to a proton. © 1990.