Search results for "Oxalate"
showing 10 items of 215 documents
Identity Double-Proton Transfer in (3Z)-3-Hydroxy-1,4-di(quinolin-2-yl)but-3-en-2-one
2003
Although there is a very fast (on the NMR timescale) double-proton transfer in (1Z,3Z)-3-hydroxy-4-quinolin-2-yl-1-quinolin-2(1H)-ylidenbut-3-en-2-one (the product of the condensation of ethyl oxalate with 2-lithiomethylquinoline), it is the only species present in chloroform solution. Comparison of the product of condensation of ethyl oxalate with 2-lithiomethyl derivatives of pyridine (recent studies) and quinoline (present studies) shows that benzoannulation considerably affects the tautomeric equilibrium. The observed changes are not only quantitative but also qualitative. Moreover, contrary to the proton transfer in the pyridine tautomers, this process is fast in the quinoline tautomer…
Synthesis, crystal structure and magnetic properties of [Cr2Cu2(bpy)4(ox)5]·2H2O. An oxalato-bridged heterometallic tetramer
2003
A new heterometallic tetramer of formula [Cr2Cu 2(bpy)4(ox)5]·2H2O (1) (bpy=2,2′-bipyridine; ox=oxalate dianion) has been prepared and characterised by single-crystal X-ray diffraction, magnetic susceptibility measurements and ESR spectroscopy. The tetranuclear unit in 1 can be viewed as the combination of two terminal [Cr(bpy)2(ox)]- units with a central oxalato-bridged copper(II) dimer. The chromium ions are in a distorted octahedral environment with metal-ligand distances ranging from 1.944(4) to 2.064(5) A. The copper(II) centres lie in an axially distorted octahedron. The axial positions are occupied by one oxygen atom belonging to the central bridging oxalate anion [O(9)-Cu(1): 2.245(…
Layered Molecule-Based Magnets Formed by Decamethylmetallocenium Cations and Two-Dimensional Bimetallic Complexes [MIIRuIII(ox)3]−(MII=;Mn, Fe, Co, C…
2001
Abstract A new series of hybrid organometallic-inorganic layered magnets with formula [Z III Cp * 2 ] [M II Ru III (ox) 3 ] ( Z III =Co and Fe; M II =Mn, Fe, Co, Cu, and Zn; ox=oxalate: Cp * =pentamethylcyclopentadienyl) has been prepared. All of these compounds are isostructural to the previously reported [ Z III Cp * 2 ] [ M II M III (ox) 3 ] ( M III =Cr, Fe) series and crystallize in the monoclinic space group C 2/ m , as found by powder X-ray diffraction analysis. They are novel examples of magnetic materials formed by bimetallic oxalate-based extended layers separated by layers of organometallic cations. The magnetic properties of all these compounds have been investigated (ac and dc m…
Molecule-Based Magnets Formed by Bimetallic Three-Dimensional Oxalate Networks and Chiral Tris(bipyridyl) Complex Cations. The Series [ZII(bpy)3][ClO…
2000
The synthesis, structure, and physical properties of the series of molecular magnets formulated as [ZII(bpy)3][ClO4][MIICrIII(ox)3] (ZII = Ru, Fe, Co, and Ni; MII = Mn, Fe, Co, Ni, Cu, and Zn; ox = oxalate dianion) are presented. All the compounds are isostructural to the [Ru(bpy)3][ClO4][MnCr(ox)3] member whose structure (cubic space group P4(1)32 with a = 15.506(2) A, Z = 4) consists of a three-dimensional bimetallic network formed by alternating MII and CrIII ions connected by oxalate anions. The identical chirality (lambda in the solved crystal) of all the metallic centers determines the 3D chiral structure adopted by these compounds. The anionic 3D sublattice leaves some holes where th…
Oxidative dehydrogenation of propane and n-butane on V-Mg based catalysts
1994
Abstract The catalytic properties of vanadium supported catalysts for the oxidative dehydrogenation of propane and n-butane has been studied. Natural Sepiolite and magnesium oxalate were used as starting support materials. Large differences in the type of crystalline phases were detected on the calcined catalysts depending on the vanadium content and nature of the support. The active and selective sites for the oxidative dehydrogenation of propane and n-butane, are related with isolated V 5+ with atetrahedral coordination. The presence of vanadium species with coordination higher than 4 negatively influence the selectivity to dehydrogenation products.
Incommensurate nature of the multilayered molecular ferromagnetic metals based on bis(ethylenedithio)tetrathiafulvalene and bimetallic oxalate comple…
2004
The salt [ET]x[MnRh(ox)(3)].CH(2)Cl(2) (x = 2.526(1)) has been obtained and characterized. This paramagnetic metal is essentially isostructural to the ferromagnetic metal [ET]y[MnCr(ox)(3)].CH(2)Cl(2) (y approximately equal to 3) and provides a definite answer on the origin of the structural disorder present on such systems. As in the ferromagnetic analogue, this material shows high electrical conductivity at room temperature (13 S.cm(-1)) and metallic behavior.
Novel chiral three-dimensional iron(III) compound exhibiting magnetic ordering at T(c) = 40 K.
2002
The preparation and crystal structure determination of the iron(III) compound of formula [(NH(4))(2)[Fe(2)O(ox)(2)Cl(2)].2H(2)O](n) (1) (ox = oxalate dianion) are reported here. Complex 1 crystallizes in the orthorhombic system, space group Fdd2, with a = 14.956(7) A, b = 23.671(9) A, c = 9.026(4) A, and Z = 8. The structure of complex 1 consists of the chiral anionic three-dimensional network [Fe(2)O(ox)(2)Cl(2)](2-) where the iron(III) ions are connected by single oxo and bisbidentate oxalato groups. The metal-metal separations through these bridging ligands are 3.384(2) and 5.496(2) A, respectively. Ammonium cations and crystallization water molecules are located in the helical pseudohex…
Influence of gel composition in the synthesis of MoVTeNb catalysts over their catalytic performance in partial propane and propylene oxidation
2010
[EN] MoVTeNb mixed oxides catalysts have been prepared by a slurry method with different molar compositions (Mo/Te ratio from 2 to 6 and Nb/(V + Nb) ratio from 0 to 0.7) in the synthesis gel leading to different crystalline phases distribution and catalytic behaviour in the partial oxidation of both propane and propylene to acrylic acid. Chemical analysis indicates that the composition of samples before and after the heat-treatment changes, especially the Te-content, since a significant amount of Te is lost during the heat-treatment step when the amount of oxalate (from niobium oxalate) increases in the synthesis gel. Thus, the nature of the crystalline phases and the catalytic performance …
One-dimensional oxalato-bridged copper(II) complexes with 3-hydroxypyridine and 2-amino-4-methylpyridine
2001
Two new one-dimensional oxalato-bridged copper(II) compounds of formula [Cu(ox)L2]n (1) and {[Cu2(ox)2L%3]·L%}n (2) [ox oxalate dianion, L3-hydroxypyridine (pyOH) and L% 2-amino-4-methylpyridine (ampy)] have been synthesized and characterized by FT-IR spectroscopy, variable-temperature magnetic measurements and single-crystal X-ray diffraction. The crystal structure of 1 comprises chains of copper atoms in which cis-[Cu(pyOH)2] 2 units are sequentially bridged by asymmetric bis-bidentate oxalato ligands with an intrachain copper‐copper separation of 5.548(1) A, . Each copper atom is six-coordinated: four oxygen atoms belonging to two bridging oxalato ligands and two nitrogen atoms from two …
ChemInform Abstract: Formation in Solution, Synthesis and Crystal Structure of μ-Oxalatobis(bis(2-pyridylcarbonyl)amido)dicopper(II).
1989
Abstract The compound μ-oxalatobis[bis(2-pyridylcarbonyl)amido] dicopper(II), [Cu 2 {(NCsH 5 CO) 2 N} 2 - (C 2 O 4 )] was synthesized and characterized by spectroscopy, EPR and diffraction methods. It crystallizes in the triclinic space group P 1 with cell constants: a =7.6793(6), b =9.238(2), c =10.007(2) A, α=83.80(1), β=68.37(1) and γ=69.44(1)°; V =617.7(3) A 3 , D (calc., Z =2)=1.80 g cm −3 , M r =667.6, F (000)=336, λ, (Mo Kα)=0.71069 A, μ (Mo Kα)=17.895 cm −1 and T =295 K. A total of 3587 data were collected over the range of 1 ⩽ θ ⩽ 30°; of these, 2391 (independent and with I⩾2σ( I )) were used in the structural analysis. The final R and R w residuals were 0.049 and 0.053, respective…