| 1. |
- Johansson, A., et al.
(författare)
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The solution thermolysis approach to molybdenum(V) alkoxides : synthesis, solid state and solution structures of the bimetallic alkoxides of molybdenum(V) and niobium(V), tantalum(V) and tungsten(VI)
- 2000
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Ingår i: Journal of the Chemical Society-Dalton Transactions. - : Royal Society of Chemistry (RSC). - 0300-9246 .- 1470-479X .- 1364-5447. ; :3, s. 387-394
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Tidskriftsartikel (refereegranskat)abstract
- No complex formation can be observed between molybdenum(VI) oxoalkoxides and the alkoxides of niobium(V) or tantalum(V) at room temperature. The bimetallic derivatives of molybdenum(V), Mo4M2O8((OPr)-Pr-i)(14), where M=Nb 1 and Ta 2, were instead isolated on cooling from the solutions of the isopropoxides in toluene subjected to a short-time reflux. The X-ray single crystal study showed both 1 and 2 to be built of ((PrO)-Pr-i)(3)M(mu-(OPr)-Pr-i)(3)MoO(mu-O)(2)MoO(mu-(OPr)-Pr-i)(2)MoO(mu-O)(2)MoO(mu-(OPr)-Pr-i)(3)M((OPr)-Pr-i)(3) non-linear chain molecules with 2 Mo-Mo bonds (2.5836(8) Angstrom) and short but non-bonding Mo-M distances (3.1791(8) Angstrom for 1 and 3.1746(8) Angstrom for 2). According to NMR and EXAFS data this structure becomes very fluxional or might even be partially broken into homometallic components in hydrocarbon solutions. The oxidation of 2 with traces of oxygen leads to the formation of Mo3Ta2O8((OPr)-Pr-i)(10) 3. Compound 3 can be isolated in a pure form from the reaction of MoO((OPr)-Pr-i)(4) with Ta((OPr)-Pr-i)(4)(OMe) 6: the presence of methoxide ligands leads to the formation of additional oxoligands via non-reductive thermolysis leading to the formation of a (CH3)(2)C(OMe)(2) ketal as organic byproduct. The molecules of 3 are 5-member rings with a MoO(mu-O)(2)MoO fragment in the basis (Mo-Mo 2.5730(13) Angstrom), coupled to two (mu-(OPr)-Pr-i)(2)Ta((OPr)-Pr-i)(3) fragments that are joined together by an oxomolybdate ligand (mu-O)(2)MoO2. According to NMR-spectroscopic data the aggregate is preserved and rigid in solution. Mo4Ta4O16((OPr)-Pr-i)(12) 4 was found to be one of the products of complete oxidation of 2 (and 3) on prolonged contact with dry oxygen. The thermal treatment of the solutions of MoO((OPr)-Pr-i)(4) and WO((OPr)-Pr-i)(4) in toluene yields (Mo4O8)-O-V(Mo,W)O-VI(2)2((OPr)-Pr-i)(12) 5 with a molecular structure very close to its homometallic analog Mo6O10((OPr)-Pr-i)(12). The complete X-ray single crystal study was carried out for the sample of 5 with (Mo4O8)-O-V(Mo0.45W0.55)O-VI(2)2((OPr)-Pr-i)(12) composition.
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| 2. |
- Seisenbaeva, G. A., et al.
(författare)
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Electrochemical synthesis, X-ray single crystal, IR spectroscopic, and quantum chemical investigation of molybdenum and tungsten hexamethoxides
- 2001
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 40:15, s. 3815-3818
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Tidskriftsartikel (refereegranskat)abstract
- The anodic oxidation of molybdenum metal in MeOH at both low anodic and cathodic current density (0.025 A/cm(2)) and electrolyte temperatures kept below 20 degreesC provides sn efficient approach to Mo(OMe)(6) (I). W(OMe)(6) (II) can be obtained from the electrolytes, prepared via anodic dissolution of tungsten, by fractional crystallization. The symmetrically independent units in the structures of I and II, being isomorphous, follow the C-1 (slightly distorted D-2d) symmetry. Theoretical calculations performed for a free molecule of I indicate that this low symmetry may be the result of the packing of the molecules in the crystal, structure and also an inherent property imposed by the bonding in this compound. Crystal data for I: Mo(OMe)(6) at 22 degrees C, a = 7.0976(13), b = 6.6103(12), and c = 12.286(2) Angstrom, beta = 90.068(3)degrees, V= 576.41(18) Angstrom (3), monoclinic P2/n, Z = 2. Crystal data for II: W(OMe)(6) at 22 degreesC, a = 7.1164(19), b = 6.6414(18), and c = 12.304(3) Angstrom, beta = 90.047(5)degrees, V = 581.5(3) Angstrom (3), monoclinic P2/n, Z = 2.
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| 3. |
- Seisenbaeva, G. A., et al.
(författare)
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Homo- and hetero-metallic rhenium oxomethoxide complexes with a M-4(mu-O)(2)(mu-OMe)(4) planar core - a new family of metal alkoxides displaying a peculiar structural disorder. Preparation and X-ray single crystal study
- 2001
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Ingår i: Journal of the Chemical Society. Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1472-7773 .- 1364-5447. ; :19, s. 2762-2768
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Tidskriftsartikel (refereegranskat)abstract
- The reaction of Re2O7 with MeOH at room temperature leads to a fine black powder. A product with the same crystal structure, according to X-ray powder data, was obtained in the form of single crystals on storage of solutions of Re2O3(OMe)(6), obtained by anodic oxidation of Re metal. It was identified as Re4O6(OMe)(12) (1) by an X-ray single crystal study. A mixed-valence complex of analogous composition and structure, Re4O6-y (OMe)(12+y) (2), earlier erroneously described as Re4O2(OMe)(16), can be obtained via anodic dissolution of Re in MeOH using high current densities. The heterometallic members of this family, Re4-xMxO6-y(OMe)(12+y) [M = Mo (3), W (4); x less than or equal to 0.55, y < 1.0], were obtained by interaction of Re2O7 with MO(OMe)(4) or M(OMe)(6) in toluene at reflux. Mo-poor samples of 3 (x 0.25) could also be obtained on storage of solutions prepared by anodic oxidation of Re, in the presence of MoO(OMe)(4). The reaction of Re2O7 with Nb(OMe)(5) or Ta(OMe)(5) in refluxing toluene gave M-4(mu -O)(2)(mu -OMe)(4)(OMe)(14)(ReO4)(2) [M = Nb (5), Ta (6)] as the only crystalline products. The compounds 1-6 are insoluble in organic solvents and display a remarkable resistance to ambient atmosphere, making them attractive precursors for soft chemical preparation of rhenium metal and alloy powders.
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| 4. |
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| 5. |
- Toprak, Muhammet, 1973-, et al.
(författare)
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Annex : Synthesis of Engineered Nanomaterials
- 2012
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Ingår i: Adverse Effects of Engineered Nanomaterials: Exposure, Toxicology, and Impact on Human Health. - : Elsevier BV. - 9780123869401 ; , s. 315-331
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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