A Combined Neutron Powder and X-Ray Single Crystal Diffraction Study of Anhydro-Iodic Acid, DIO3 · I2O5, at 293 K

Abstract

The crystal structure of deuterated anhydro-iodic acid, DIO3 · I2O5, at 293 K has been determined from neutron powder and X-ray single crystal diffraction data. DIO3 · I2O5 is monoclinic, space group P 21/n, with a = 7.581(2), b = 7.713(1), c = 11.405(1), β = 90.20(1)°, and Z = 4. This work confirms that the compound often written HI3O8 is an addition compound of HIO3 and I2O5. The DIO3 molecule is pyramidal with I-O bond distances of 1.795(2), 1.799(2), and 1.890(2) Å, the latter also bonded to D. The I2O5 molecule has approximate mirror symmetry. The four terminal I-O distances are in the range 1.787(2)-1.800(20 Å, while the two central I-O distances are 1.957(2) and 1.959(2) Å, with an I-O-I angle of 126.0(1)°. The DIO3 and I2O5 molecules are linked by a hydrogen bond (D ··· O 1.81(2) Å and O ··· O 2.755(2) Å). The three-dimensional structure is described as built from edge and corner-sharing bicapped trigonal prisms of oxygen atoms around iodine and its lone pair electrons.