Synthesis and Characterization of 2,2-Biimidazole Complexes of Oxocations of Molybdenum (VI, V) and Uranium(VI)

Abstract

2,2′-Biimidazole complexes of MoO₂ ⁺², MoO₂ ⁺ and UO₂ ⁺² have been prepared and characterized by elemental analysis, conductance; and ¹H NMR, IR and electronic spectra. Two types of complexes have been identified. Those obtained from slightly acidic solutions have the formulae MoO₂ (H₂bim)Cl₂.2H₂O 1, UO₂(H₂bim) (Ac)₂ 2 and UO₂(H₂bim)Cl₂.2H₂O 3; whereas those from alkaline solutions have the formulae Mo₂O₄(Hbim)₂.2H₂O 4, and MO₂(Hbim)₂ (M = Mo(VI) 5, U(VI) 6). The infrared spectra of these complexes show characteristic biimidazole frequencies in the 3200–2500, 1550–1000 and 750 cm⁻¹ regions as well as metal oxygen double bonds in the 900 cm⁻¹ region. The stoichiometries of the acetate complex has been confirmed from ¹H NMR signal ratios of bimidazole to acetate protons at 7.3 and 2.3 ppm, respectively. The electronic spectrum of molybdenum(V) complex showed d-d transition band at ≃13,500 cm⁻¹ in accord with that reported for copper (d⁹) imidazole complexes; as well as peaks due to charge transfer bands at 30,000–26,000 cm⁻¹ Peaks assignable to BIM → U(VI) were located at ≃26,600 cm⁻¹. The most probable structures of these complexes have been suggested.