X-Ray Structure, Electrochemical and Electronic Spectroscopic Examination of Cobaloximatic Acid: Hydro-trans-diiodobis(ethanedioximato(1-)-N,N′)cobaltate(III). Extended Intermolecular O-H-O Bridging in the Solid
2014
Mégnamisi-Bélombé, Michel | Jokwi, Irene | Ngameni, Emmanuel | Roux, Robert | Nuber, Bernhard
The structure of the cobaloximatic acid, hydro-trans-diiodobis(ethanedioximato(1-)-N,N′)cobaltate(III), has been determined by X-ray diffraction. Crystal data: C₄H₇CoI₂N₄O₄, Mᵣ = 487.87; monoclinic space group P2₁/a (C₂ₕ⁵); a = 10.795(7), b = 9.003(7), c = 11.881(6) Å; β = 97.29(6)°; V = 1145.35 ų; Z = 4; dc = 2.83 Mg m⁻³. Rw (R) = 3.6 (3.9)% for 3064 observed independent reflections and 148 parameters. The coordination geometry around Coᴵᴵᴵ is a distorted (4 + 2) octahedron of four chelating equatorial N atoms and two apical iodides. The compound is most adequately formulated as a monovalent strong acid: H(Co(GH)₂I₂) (GH- = ethanedioximate or glyoximate). The H atoms of the oxime groups are involved in the usual intramolecular, as well as in much stronger intermolecular O-H-O bridgings (O ••• Oᵢₙₜᵣₐₘₒₗ = 2.613-2.631, O ••• Oᵢₙₜᵣₐₘₒₗ = 2.454 A). The “acidic” H atom of each molecule participates in the intermolecular bridging which extends throughout the structure, and propagates nearly parallel to the [101] crystallographic direction. The redox properties of the present compound were examined by cyclic voltammetry in acetonitrile solution at room temperature. Redox waves attributed to the reduction of Coᴵᴵᴵ and to the oxidation of I⁻ were observed, along with a wave which may be linked to the reduction of the “acidic” proton
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