Crystal structures of two new heptamolybdates and of a pyrazole incorporating a γ-octamolybdate anion
Introduction
It is interesting to study the interaction between MoO3 and molecules of biological interest such as imidazole (in the presence of the calcium(II) cation) and pyrazole. Moreover, the interaction between MoO3 and urea, to our knowledge, has not been previously described. This study is of interest because of the biological importance of both molybdenum(VI) and urea. Moreover, MoO3 can act as a catalyst in the transformation of small molecules such as methanol, which is oxidised to formaldehyde [1]. Here, we present a study of the possible changes produced in the urea molecule by MoO3, including its hydrolysis acid [2] by the effect of the H+ proceeding from MoO3 in aqueous solution. Urea is one of the world’s most important chemicals because of its wide use in different areas [3].
As a result of our study, we report on two new heptamolybdates, one of them with imidazole and calcium [(Himi)4][Ca(H2O)6(μ-O)2][Mo7O24]·2(imi)·3H2O (1), and the other with urea and ammonium cations [CO(NH2)2H]3(NH4)9[Mo7O24]2·5[CO(NH2)2]·4H2O (2). We also report a new γ-octamolybdate of pyrazole [(Hpyr)4][(pyr)2Mo8O26]CH3COCH3·2H2O (3).
To the best of our knowledge, no data for isomolybdates of mixed organic and calcium cations as well as urea and ammonium are available, this being the first time that a linear composite with alternating Mo7O24 and Ca(H2O)6 units is described.
Moreover, organic isopolymolybdates draw great interest because of their photochemical and photochromic properties as well as being potential antitumour and anti-VIH agents [4], [5], [6], [7].
Section snippets
General procedures and instrumentation
All chemicals were commercially available reagent grade. Deionized water was used for all syntheses. Elemental analyses (C, H and N) were performed with an EA 1108 CHNS-O automatic analyser. Calcium was determined using a Varian Spectra-10 PLUS atomic absorption spectrometer. IR spectra were recorded in the range 4000–250 cm−1 on a Nicolet 710 FTIR spectrophotometer using KBr pellets. 1H NMR spectra were collected on a Bruker WP-200 SY at 400 MHz with TMS as internal standard after dilution of
Preparation of [(Himi)4][Ca(H2O)6(μ-O)2][Mo7O24]·2(imi)·3H2O (1)
A suspension of molybdenum trioxide (2.88 g, 20 mmol), imidazole (2.72 g, 40 mmol) and 10 cm3 of sulfuric acid (18 M) in deionized water (1.1 l), was heated under reflux for 4 h. The initial pH 2.5 was raised to pH 5.8 by adding calcium hydroxide; then the suspension was filtered and from the solution, by slow evaporation at room temperature, colourless crystals suitable for X-ray analyses were obtained. Anal. Calc. for 1, C18H46Mo7N12O35Ca: C, 12.7; H, 2.7; Ca, 2.4; N, 9.9. Found: C, 12.4; H,
Crystal structures determination and refinement
For compounds 1–3, irregular prismatic colourless crystals for 1 and 3 (0.07×0.5×0.4 and 0.07×0.05×0.04 mm, respectively) and hexagonal colourless crystals for 2 (0.4×0.25×0.25 mm) were mounted on a glass fiber and used for data collection. Cell constants and an orientation matrix for data collection were obtained by least-squares refinement of the diffraction data from 25 reflections in the range 10<θ<25° for 1 and 3, in a Stoe Siemens AED-2 diffractometer and in the range of 10<θ<19° in an
Synthesis
One of the main advantages of wet chemistry methods to obtain polyoxometalates is that weak interactions (hydrogen bonds, van der Waals, hydrophile–hydrophobic interactions, etc.) are not broken at temperatures below ca. 70°C. They are involved in the self-assembling of molecular precursors and play an important role during the formation of the polyanion network or of supramolecular associations [17].
The preparations for all compounds were similar, with the exception of the heptamolybdates
Supplementary material
Crystallographic data (without structure factors) of the structures described in this publication have been deposited with the Cambridge Crystallographic Data Centre as no. CCDC-125423 (1), CCDC-125424 (2) and CCDC-125425 (3). Copies of the data can be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: +44-1223-336-033; e-mail: [email protected]). Figures S1 and S2 are available from the authors upon request.
Acknowledgements
P.G. gratefully acknowledges support from the Gobierno de Canarias (Project No. 245-108/98). Thanks are also due to Mrs P. Agnew for correcting the English text.
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Oxidation of sulfides in aqueous media catalyzed by pyrazole-oxidoperoxido-molybdenum(VI) complexes
2020, Inorganica Chimica ActaCitation Excerpt :All of these pyrazole-derived ligands and their respective coordination modes can be found in a wide selection of mononuclear and dinuclear oxidomolybdenum(VI) complexes [9–22], with representative examples being [MoO2Cl2(L1)2], [MoO2Cl2(L2)], [(L3)MoO3], [MoO2Cl(L3)]n+, [MoO(O2)2(L1)2], [(MoO2Cl(L1)2)2(μ2-O)] and [(MoO2(L3))2(μ2-O)]n+, where L1 indicates a monodentate ligand (e.g. pzH, 3-methylpyrazole (Mepz) or 3,5-dimethylpyrazole (dmpz)), L2 indicates a bidentate ligand (e.g. bis(pyrazolyl)alkane (bpza)), and L3 indicates a tridentate ligand (e.g. HC(pz)3 or HC(3,5-Me2pz)3). The structural diversity of discrete oxidomolybdenum(VI) complexes bearing coordinatively bound pyrazole-derived ligands extends to high-nuclearity molecules such as the tetranuclear complex [Mo4O16(dmpz)6] (consisting of a symmetrical {MoO(μ-O)(O2)(dmpz)}2 binuclear core to which two [MoO2(O2)(dmpz)2] units are connected) [16,18], the compounds [HL1]4[Mo8O26(L1)2] which incorporate γ-octamolybdate anions [19,23], and the tetraperoxido-octamolybdate derivatives [HL1]4[Mo8O22(O2)4(L1)2]·nH2O [18,19]. Oxido- and oxidoperoxido-molybdenum(VI) complexes with organic ligands are well known for their catalytic activity in olefin epoxidation with hydroperoxides [24–26].
Application of central composite design to the partition of perrhenate anion in aqueous two phase system Na <inf>2</inf> MoO <inf>4</inf> + PEG 4000 + H <inf>2</inf> O
2019, Journal of Molecular LiquidsCitation Excerpt :On the other hand, molybdenum can be present as polyoxometalates, whose form a class of inorganic compounds that are unique in terms of molecular and electronic structural versatility, reactivity, and relevance for the analytical chemistry, catalysis, biology, medicine, geochemistry, materials science, topology, nanomaterials and supramolecular chemistry [2,3]. Moreover, hybrid organic isopolymolybdates arouse great interest due to their photochemical and photo-chromic properties as well as being potential antitumour and anti-HIV agents [4]. Rhenium is recovered during pyrometallurgical processing of molybdenum sulfide and copper sulfide ores; the traditional technology involves removing rhenium (VII) oxide, Re2O7, from the sulfurous gas phase generated during roasting process (in molybdenum processing) and smelting (in copper processing) [5,6].
Stabilization of β-octamolybdate with large counterions
2017, Journal of Molecular StructureThe Anderson-Evans polyoxometalate: From inorganic building blocks via hybrid organic-inorganic structures to tomorrows "Bio-POM"
2016, Coordination Chemistry ReviewsCitation Excerpt :Interestingly, when ZnII and NiII were used as heteroatoms and tris-CH3 and tris-CH2OH as organic ligands, double-sided χ-isomers were also obtained despite using the route involving re-arrangement of octamolybdate (Fig. 7, C4) which resulted in loss of the threefold symmetry [86]. There exist 177 crystal structures of “extended” (see Section 2.2) structures in the AlIIIMo6 [61,69,74,76–78,81,82,173,191–205], CrIIIMo6 [56,60,63,65–69,73,76,79,81,173,177,191,194,195,199,201,204,206–217], NiIIMo6 [93,175,218–220], CoII/IIIMo6 [221–223] FeIIIMo6 [224], CuIIMo6 [174,225–229], ZnIIMo6 [230], AsIIIMo6 [229–232], Mo7 [112,176,193,233–245], TeVIMo6 [70,246–250], TeVIW6 [70,75,251–253], IVIIMo6 [82,97,193,214,254–257], W7 [172,258], PtIVMo6 [259,260] and PtIVW6 [261] systems as of March 2015. The following paragraphs looks into some interesting organic-inorganic compounds in terms of structure and crystal packing.