Further Evidence for the Tetraoxoiodate(V) Anion, IO43-: Hydrothermal Syntheses and Structures of Ba[(MoO2)6(IO4)2O4]·H2O and Ba3[(MoO2)2(IO6)2]·2H2O

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Abstract
The hydrothermal reaction of MoO3 with BaH3IO6 at 180 °C for 3 days results in the formation of Ba[(MoO2)6(IO4)2O4]·H2O (1). Under similar conditions, the reaction of Ba(OH)2·8H2O with MoO3 and Ba(IO4)2·6H2O yields Ba3[(MoO2)2(IO6)2]·2H2O (2). The structure of 1, determined by single-crystal X-ray diffraction, consists of corner- and edge-sharing distorted MoO6 octahedra that create two-dimensional slabs. Contained within this molybdenum oxide framework are approximately C2v tetraoxoiodate(V) anions, IO43-, that are involved in bonding with five Mo(VI) centers. The two equatorial oxygen atoms of the IO43- anion chelate a single Mo(VI) center, whereas the axial atoms are μ3-oxo groups and complete the octahedra of four MoO6 units. The coordination of the tetraoxoiodate(V) anion to these five highly electropositive centers is probably responsible for stabilizing the substantial anionic charge of this anion. The Ba2+ cations separate the layers from one another and form long ionic contacts with neighboring oxygen atoms and a water molecule. Compound 2 also contains distorted MoO6 octahedra. However, these solely edge-share with octahedral hexaoxoiodate(VII), IO65-, anions to form zigzagging one-dimensional, [(MoO2)(IO6)]3-, chains that are polar. These chains are separated from one another by Ba2+ cations that are coordinated by additional water molecules. Bond valence sums for the iodine atoms in 1 and 2 are 5.01 and 7.03, respectively. Crystallographic data: 1, monoclinic, space group C2/c, a = 13.584(1) Å, b = 7.3977(7) Å, c = 20.736(2) Å, β = 108.244(2)°, Z = 4; 2, orthorhombic, space group Fdd2, a = 13.356(7) Å, b = 45.54(2) Å, c = 4.867(3) Å, Z = 8.

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