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Exploring the Chemical Reactivity between Carbon Dioxide and Three Transition Metals (Au, Pt, and Re) at High-Pressure, High-Temperature Conditions
2016
The role of carbon dioxide, CO2, as oxidizing agent at high pressures and temperatures is evaluated by studying its chemical reactivity with three transition metals: Au, Pt, and Re. We report systematic X-ray diffraction measurements up to 48 GPa and 2400 K using synchrotron radiation and laser-heating diamond-anvil cells. No evidence of reaction was found in Au and Pt samples in this pressure–temperature range. In the Re + CO2 system, however, a strongly–driven redox reaction occurs at P > 8 GPa and T > 1500 K, and orthorhombic β-ReO2 is formed. This rhenium oxide phase is stable at least up to 48 GPa and 2400 K and was recovered at ambient conditions. Raman spectroscopy data confirm graph…
Neutral one-dimensional metal chains consisting of alternating anionic and cationic rhodium complexes.
2012
The metallophilic interactions were investigated within chains of oppositely charged rhodium carbonyl complexes. The cationic [Rh(CO)(2)(L)](+) (L = 2,2'-bipyridine and 1,10-phenanthroline) and anionic [RhCl(2)(CO)(2)](-) units were self-assembled into one dimensional rhodium chains supported by electrostatic interactions. The array of Rh centers in {[Rh(CO)(2)(2,2'-bpy)][RhCl(2)(CO)(2)]}(n) was found to be nearly linear with a Rh···Rh···Rh angle of 170.927(11)° and Rh···Rh distances of 3.3174(5) Å and 3.4116(5) Å. The crystal structure of {[Rh(CO)(2)(1,10-phen)][RhCl(2)(CO)(2)]} consisted of two sets of crystallographically independent chains with slightly different Rh···Rh···Rh angles (17…
Mixed Titanium–Hafnium Chloridometallate Complexes
2007
The addition of either NEt 3 BzCl or [Ph 3 PNPPh 3 ]Cl (1 equiv. chloride per metal) to a 1:1 mixture of HfCl 4 and TiCl 3 in SOCl 2 results in Ti oxidation and leads to the corresponding salts of the [TiHfCl 10 ] 2- ion. A solution IR investigation in the v(M-Cl) region indicates that this ion is in equilibrium with the homodimetallic [Ti 2 Cl 10 ] 2- and [Hf 2 Cl 10 ] 2- ions. An X-ray study of the NEt 3 Bz + salt reveals an edge-sharing bioctahedral dianion sitting on a crystallographic inversion centre. The crystal is a solid solution of different species with compositional disorder at the metal site, each metal position having the occupancy Ti 0.685 Hf 0.315 . The M-M and M-Cl distance…
Density functional theory based screening of ternary alkali-transition metal borohydrides: a computational material design project.
2009
We present a computational screening study of ternary metal borohydrides for reversible hydrogen storage based on density functional theory. We investigate the stability and decomposition of alloys containing 1 alkali metal atom, Li, Na, or K M1; and 1 alkali, alkaline earth or 3d / 4d transition metal atom M2 plus two to five BH4 groups, i.e., M1M2BH42‐5, using a number of model structures with trigonal, tetrahedral, octahedral, and free coordination of the metal borohydride complexes. Of the over 700 investigated structures, about 20 were predicted to form potentially stable alloys with promising decomposition energies. The M1Al/ Mn/ FeBH44, Li/ NaZnBH43, and Na/ KNi/ CoBH43 alloys are …
Tetraurea calix[4]arenes with sulfur functions: synthesis, dimerization to capsules, and self-assembly on gold.
2007
Various calix[4]arene derivatives, fixed in the cone conformation by decylether groups and functionalized at their wide rim by urea residues, were synthesized. In two compounds (4f,g) sulfur functions were attached to the urea groups via different spacers in order to allow binding to metal surfaces. While they exist as single molecules in polar solvents, tetraurea calix[4]arenes of this type (4) combine to form dimeric capsules in aprotic, apolar solvents. A solvent molecule is usually included in such a capsule, if no guest with a higher affinity is present. In the presence of an equimolar amount of the tetratosylurea 5, the exclusive formation of heterodimers, consisting of one molecule o…
Low temperature total oxidation of toluene by bimetallic Au–Ir catalysts
2017
9 Figuras.- 3 Tablas.- Información suplementaria disponible en la página web del editor
2-Tetrahydrofurfuroxo-vanadium-(III) and -(IV) complexes. Synthesis, structures and reactivities of [V2Mg2(μ3,δ2-thffo)2(μ,δ2-thffo)4Cl4]· 2CH2Cl2 an…
1997
Vanadium complexes of 2-tetrahydrofurfuroxide (2-tetrahydrofurylmethoxide) (thffo) with the metal in oxidation state III and IV have been prepared and characterized. The reaction of [VCl3(thf)3] with 1.5 equivalents of [Mg(thffo)2] in tetrahydrofuran (thf) or CH2Cl2 led to the formation of [V2Mg2(µ3,η2-thffo)2(µ,η2-thffo)4Cl4]· 2CH2Cl21. Its structure consists of centrosymmetric tetranuclear molecules and CH2Cl2 of crystallization. Two Mg and two V atoms have distorted octahedral geometry and form a nearly regular Mg2V2 rhombus. The V · · · V distance is 3.266(2) A. The reaction of [VOCl2(thf)2] with Na(thffo) in thf yielded [V2(µ,η2-thffo)2Cl2O2] 2. Two VOCl units are linked by alkoxide ox…
Synergetic effect of gold in Au/Pd catalysts during hydrodesulfurization reactions of model compounds
2003
Abstract The simultaneous formation of colloidal dispersions of Pd and Au metal particles protected by the organic polymer polyvinylpyrrolidone (PVP) in reducing alcohol solution was used for the synthesis of new silica-supported monometallic and bimetallic Au x Pd y catalysts with different x / y ratios. The samples, with a 2 wt% total metal loading, after air calcinations at 673 K to remove the PVP, were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and FTIR spectra of chemisorbed CO. Formation of alloyed Au x Pd y particles of different metal composition with consequent modification of their electronic and geometric properties was ascertained. The catalytic activi…
A Novel 1D-AF Hybrid Organic-Inorganic Chromium(II) Methyl Phosphonate Dihydrate: Synthesis, X-Ray Crystal and Molecular Structure, and Magnetic Prop…
2010
Light-blue crystals of chromium(II) methyl phosphonate dihydrate, [Cr(CH(3)PO(3))(H(2)O)].H(2)O, were obtained in water by mixing filtered solutions of methylphosphonic acid and chromium(II) chloride in the presence of urea in an inert atmosphere. The compound was characterized by elemental analysis, TGA-DSC, X-ray crystallography, magnetic measurements, and UV-visible and FT-IR spectroscopies. The crystal and molecular structures (orthorhombic Pnma (no. 62): a = 4.4714(5) A, b = 6.8762(7) A, c = 19.180(2) A, Z = 4) have been solved using single-crystal X-ray diffraction. The chromium(II) ion is six-coordinated by oxygens (4 + 2) to form an elongated octahedron, with the four equatorial oxy…
Synthesis and Spectroscopic Characterisation ofbis-Complexes of Cobalt(II), Nickel(II) and Copper(II) with N,N,N′N′-Tetraethylpyridinecarboxamide
1994
Abstract Bis-complexes of Co(II), Ni(II) and Cu(II) with tedpa (N,N,N′N′-tetraethyl-pyridinedicarboxamide) having the general formula [M(tedpa)2]X2 (X = ClO4, PF6) have been synthesized and characterised by i.r., electronic and e.p.r. spectra. The spectroscopic results suggest that the tedpa acts in these compounds as tridentate ligand through two oxygen atoms and a nitrogen (from the pyridine ring) atom. A distorted octahedral environment (MN2O4 chromophores) for the metal atoms is inferred from the spectroscopic data.