Molybdotellurates containing the 1-methyl-, 2-methyl- and 4-methyl imidazolium cations

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Four molybdotellurates containing the 1-methylimidazolium, 2-methylimidazolium and 4-methylimidazolium cations have been synthesized and their structures: [2-H2-methyl-imz]6[TeMo6O24]·2H2O (2), [2-H2-methyl-imz]6[TeMo6O24]·2(2-H-methyl-imz)·2H2O (3)and [4-H2-methyl-imz]6[TeMo6O24]·Te(OH)6(4) determined by X-ray diffraction methods. The protonated organic bases are bonded to the anion in the crystal by hydrogen bonds, except for (4) where the crystal structure consists of discrete [TeMo6O24]6−anions and Te(OH)6units, both bonded to 4-methylimidazolium cations by hydrogen bonds. The hydrogen bonds were studied as a function of the unit charge of the oxygen atoms of the [TeMo6O24]6−anion. Distortions of the central octahedron of polyanions of formula [XMo6O24]n−(X = AlIII, MoVI, TeVIand IVII), and polyanions of formula [H6YMo6O24]n−, (Y = CoII, CuII, ZnII, CrIII, RhIIIand PtIV) are discussed. 95Mo n.m.r spectroscopy of compounds [1-H2-methyl-imz]6[Te-Mo6O24]·Te(OH)6(1), (2)and (4) indicates the existence of an octahedral oxygen atom arrangement around the molybdenum and a pH variation experiment, carried out with compound (1), confirmed the existence of hydrolytic processes of the compounds in aqueous solution. 125Te n.m.r. studies permitted identification of the Te atom in the [TeMo6O24]6−kernel in all compounds; the presence of two different Te(OH)6moieties in compounds (1) and (4) was also detected. The similarity between the spectra of both compounds could indicate that (1) has the same structural arrangement as (4). Finally, the thermal behaviour and the thermal stabilities of the complexes as a function of the organic cation were studied.

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