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ABSTRACT: Mononuclear unsymmetrical N-heterocyclic carbene-gold complexes and the corresponding solid catalysts in which a gold-carbene complex has been immobilized on silica gel, ordered mesoporous silica (MCM-41), and delaminated zeolite (ITQ-2) have been prepared. These new catalysts have been tested in the hydrogenation of alkenes and the Suzuki cross-coupling reaction to afford selectively non-symmetrical biaryls. These reactions were studied with the soluble as well as with the heterogenized counterpart catalysts. The high accessibility introduced by the structure of the supports allows the preparation of highly efficient immobilized catalysts with TOFs up to 400 h−1. Moreover, the heterogenized complexes were reused and no deactivation of the catalysts can be observed.
Advanced Synthesis & Catalysis 04/2013; 348:1899-1907. · 6.05 Impact Factor
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ABSTRACT: By using the bent linker 4,4'-(hexafluoroisopropylidene)bis(benzoic acid) (H(2)hippb), whose central atom is an sp(3) carbon, a new In(III) MOF has been obtained. The structure is described as thick layers with the bent geometry of the ligand leading to the formation of square-shaped channels, which run inside the framework layers. This microporous, thermally stable compound has been proved to be an efficient heterogeneous catalyst for acetalization of aldehydes. Differences in the catalytic activity when a compound with empty or filled channels is used demonstrate that the catalytic reactions take place inside the pores.
Chemistry of Materials 04/2013; 20:72-76. · 7.29 Impact Factor
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Advanced Synthesis & Catalysis 10/2007; 349(16):2470 - 2476. · 6.05 Impact Factor
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ABSTRACT: A series of homogeneous and heterogenized gold metal complexes show high activity and selectivity for the homocoupling of a large variety of aryl boronic acids, being of general utility for the synthesis of C2-symmetric biaryls.
Chemical Communications 05/2005; · 6.17 Impact Factor
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ABSTRACT: Four novel metal-organic frameworks (MOFs) [In(BDC) 1.5 (bipy)] (1), [In 2 (OH) 2 (BDC) 2 (phen) 2 ] (2), [In(BTC)(H 2 O)(bipy)] (3), and [In(BTC)(H 2 O)(phen)] (4) (BDC) 1,4-benzendicarboxylic acid, BTC) 1,3,5-benzenetricarboxylic acid, bipy) 2,2′-bipyridyl, phen) o-phenantroline) were synthesized and their structures were determined by X-ray single-crystal diffraction. Structurally speaking we can conclude that while the metal/connector/chelate rate is 1:1:1, the introduction of a chelate ligand, such as bipy or phen, blocks the possibility of connections in one direction, inducting the formation of 2D structures. In the case of compound 1, the extra one-half of BDC ligand per indium favors the eight coordination of the metal and drives the formation of a catenated 3D structure. Topological studies on the four compounds show one inclined catenation of hexagonal layers for 1 and three interdigitated layered structures with 2D topologies of type (4 4), (6 3), and (4.8 2) for 2, 3, and 4 compounds, respectively. Three of the new In compounds are active and selective acid catalyst in acetalization of aldehydes.
Chemistry of Materials 01/2005; · 7.29 Impact Factor
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ABSTRACT: Two series of solid catalysts in which a chiral palladium or nickel complex with Schiff bases as ligands have been immobilized on ordered mesoporous silica supports (MCM-41), delaminated ITQ-2, ITQ-6 zeolites and amorphous silica have been prepared. Hydrogenation of alkenes and imines was studied with the homogeneous as well as with the counterpart heterogenized catalysts. The high accessibility introduced by the structure of the supports allows the preparation of highly efficient immobilized catalysts with TOFs of 1,000,000 h−1. A moderate acidity in the support increases the catalytic activity considerably, and the easy recoverable immobilized catalysts can duplicate the activity of the homogeneous analogues. No deactivation of the catalysts was observed after repeated recycling.
Advanced Synthesis & Catalysis 09/2004; 346(11):1316 - 1328. · 6.05 Impact Factor
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ABSTRACT: The synthesis, structure, thermal stability, and catalytic properties are reported for a chiral germanate, Ge9O19(OH)2(N2C2H10)2(N2C2H8)0.5H2O, ICMM6. It is orthorhombic, of space group C2221, and has unit cell dimensions a = 12.156(3) Å, b = 13.960(4) Å, c = 14.258(4) Å, volume 2419.6(11) Å3, and Z = 4. Three kinds of interconnected helical 8-, 11-, and 11-rings channels are present in the 3D framework. ICMM6 is an active chiral catalyst for the Michael addition reaction and acetalization of aldehydes. It is stable in water and organic solvents and can be recovered and reused at least four times without losing either its structure or its reactivity.
Chemistry of Materials 01/2004; · 7.29 Impact Factor
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ABSTRACT: Cinchonidine and cinchonine have been grafted onto pure silica MCM-41. It has been shown that both supported alkaloids are active catalysts for the Michael addition of ethyl 2-oxocyclopentanecarboxylate and methyl vinyl ketone, anchored cinchonidine being more active and enantioselective than anchored cinchonine. The study of the influence of the polarity of the solvent and reaction temperature on the optical induction shows that there is not a direct correlation between solvent polarity and enantioselectivity, and the maximum optical yield was obtained between 278 and 273 K.
Catalysis Letters 09/2002; 82(3):237-242. · 2.24 Impact Factor
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ABSTRACT: The new hybrid inorganic-organic polymer In(2)(OH)(3)[O(4)C(8)H(4)](1.5) has been hydrothermally obtained. Conditions for the synthesis are reported. The crystal structure of this material has been established by single-crystal X-ray diffraction: it is monoclinic, with space group P2(1)/c (Nomicron. 14), a = 6.772(1) A, b = 10.329(2) A, c = 20.152(3) A, beta = 97.573(3) degrees. The In atoms are octahedrally coordinated by three hydroxide groups and three different molecules of carboxylate ligand. The resulting polymeric 3D structure can be envisaged as having been generated from a honeycomb (6,3) 2D that is cross-linked by the BDC organic anions. Data of IR and TGA-DTA studies, as well as the results of reduction of nitroaromatics and selective oxidation of organic sulfide reactions catalyzed by the new material, are reported.
Inorganic Chemistry 06/2002; 41(9):2429-32. · 4.60 Impact Factor
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ABSTRACT: Ge5O11H[C6N2H13] has been hydrothermally synthesized. The structure of the material has been determined by single-crystal X-ray diffraction. This novel layered germanate consists of an alternation of [Ge5O11H]− inorganic sheets and monoprotonated 1,4-diazabicyclo-[2,2,2]-octane molecules. It exhibits an arrangement of 4- and 10-ring in infinite layers not observed before. The catalytic activity in Michael reactions has been tested showing that the addition occurs at the amine centers in the interlayer space. Reuse of the catalyst and the persistence of its structure after recovering has been proved.
Chemistry of Materials 01/2002; · 7.29 Impact Factor
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ABSTRACT: The copper(I) complex [Cu(NH3)2]+ has been formed in situ during the ferrierite framework constitution. The structure of the material has been determined by single-crystal X-ray diffraction. The obtained formula is [Cu0.34(NH3)0.68]0.34+(Si35.66 Al0.34O72)0.34-·(C3H9N)2 (NH3)1.6. Along the 10-ring channel is housed a row of linear [Cu(NH3)2]+ complex. The copper atom is situated in an inversion center and bonded to two NH3 molecules at 2.21 Å. The compound that is white and diamagnetic as synthesized becomes blue and paramagnetic after heating to 800 °C and cooling to room temperature. The oxidation of Cu(I) to Cu(II) has been corroborated by magnetic susceptibility measurements. This material behaves as a good catalyst in the cyclopropanation of alkenes and sulfide oxidation reactions. It can be recovered and reused, retaining most of its catalytic activity.
Chemistry of Materials 03/2001; · 7.29 Impact Factor
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ABSTRACT: The oxidation of bulky thioethers has been carried out on Ti-Beta and Ti-MCM-41 catalysts, using H2O2 andt-butyl hydroperoxide (TBHP) as oxidants. The intrinsic activity of Ti-Beta was higher than that of Ti-MCM-41 for the oxidation of methyl phenyl sulfide which can penetrate in the pores of Beta, while in the case of the larger isopentyl phenyl sulfide, which diffuses more slowly in Ti-Beta zeolite, Ti-MCM-41 gives a larger activity. Ti-Beta is able to perform better for the more demanding oxidation of sulfoxides to sulfones giving, therefore, higher selectivities to sulfones than Ti-MCM-41. Similar results were obtained when using either H2O2 or TBHP as oxidants. However, the sterical effects were enhanced when TBHP was used as oxidant.
Catalysis Letters 08/1996; 39(3):153-156. · 2.24 Impact Factor
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ABSTRACT: The hydrogenation of aromatics, i.e. benzene, toluene, -methylstyrene, anisole, and ethyl benzoate, can be carried out under a very low (1/12000) catalyst to substrate ratio, and mild reaction conditions (80C, 6 atm of H2O), on Rh and Ni organometallic complexes anchored on USY zeolites. A strong cooperative effect between the faujasite surface and the transition metal surface complex is thought to be responsible for the simultaneous enhancement of concentrations of arene and H2 in the neighborhood of the catalytic centers, and for the observed electronic effects.
Catalysis Letters 08/1995; 32(3):313-318. · 2.24 Impact Factor
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ABSTRACT: A new general method to heterogenise porphyrins and different metalloporphyrins (Co, Fe) on silica, mesoporous MCM-41 and delaminated zeolites ITQ-2 and ITQ-6 yields stable materials, which act as active catalysts for the electrochemical oxygen reduction, without catalyst desorption from the electrode.
Catalysis Letters. 101(1):99-103.
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ABSTRACT: Porphyrins and different metalloporphyrins have been synthesised and heterogenised on robust inorganic solids such as silica gel, purely siliceous MCM-41, and delaminated zeolites ITQ-2 and ITQ-6. Two different strategies for preparation of these catalysts have been explored, mainly based on immobilisation of a functionalisated porphyrin (route A) or heterogenisation of an aromatic aldehyde and consecutive porphyrin formation (route B). Route A yields stable materials and allows introduction of a larger quantity of metalloporphyrin onto the support (contents ranged from 0.3 to 0.4 mmol g−1) whereas route B was unsuccessful and no evidence was found to support the porphyrin formation. A multitechnique approach is employed for characterisation of samples and their catalytic behaviour has been tested in the electroreduction of oxygen. A cyclic voltammetry investigation, at varying scan rate, was carried out in an attempt to elucidate the net reaction for the oxygen reduction. The synthesised metalloporphyrins are active for electrocatalytic reduction of oxygen by a two-electron mechanism, producing hydrogen peroxide. The comparison between homogeneous and heterogenised catalysts confirms that heterogenisation avoids the catalyst desorption (lost of activity) from the electrode. Catalytic activity is directly related with the content of metalloporphyrin in heterogenised materials that are addressable electronically.
Journal of Molecular Catalysis A: Chemical. 246(1-2):109-117.
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ABSTRACT: We present a widely applicable approach for the preparation of Pd-complexes supported on silica-based mesoporous and laminar inorganic solids (silica gel, purely siliceous and acidic MCM-41, and delaminated zeolites ITQ-2 and ITQ-6) which involves the use of the Schiff bases 2-tert-butyl-4-methyl-6{(E)-[(2S)-1-(1-arylmethyl)pyrrolidinyl]imino}methylphenol (aryl=phenyl, 1-naphthyl, 2-naphthyl) as anchored ligands. As an extension of our research in “recyclable catalytic systems” we report results demonstrating the reactivity and recyclability of these systems for the Heck reaction (in a biphasic mode using ethylene glycol and toluene) and Suzuki coupling under phosphine-free conditions. The complexes are insensitive to oxygen or moisture, and no change of their activity was observed when exposed to an open system during the usual operation. No palladium black was observed after an extended reaction time and no residual palladium was detected from the filtrate at the end of the reaction.
Advanced Synthesis & Catalysis. 346(13-15):1758-1764.
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Journal of Molecular Catalysis A Chemical 194:137-152. · 2.95 Impact Factor
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ABSTRACT: A new family of rare-earth polymeric framework RPF-4 has been obtained and its structure solved from an intrinsically triple twinned crystal. The framework formed by a H-O bond free rare-earth matrix, with the Ln atoms separated in two directions, makes them very promising materials for light-emitting diodes. The properties of the materials as heterogeneous catalysts are reported, too. IR spectroscopy suggests the presence of a peroxo complex that acts as active species in the oxidation reaction.
Crystal Growth & Design 8(2):378-380. · 4.72 Impact Factor
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ABSTRACT: The synthesis and characterization of optically active complexes containing organic amides [-C(O)NHR] of the type [RhCl(COD)L], [RhCl(CO)2L], [RhCl(PPh3)2L], [RuCl2(COD)L], [RuCl2(PPh3)2L], [Co(acac)L]X and [Ni(acac)L]X, where L = (S)-2-t-butylaminocarbonylpyrrolidine or (S)-2-(3-triethoxysilyl)propylaminocarbonylpyrrolidine are reported. Their cationic species were prepared in the presence of a non-coordinating counterion (X = PF6− or ClO4−). The amino acid derivative is bi-dentate with N,N-coordination. The metal complexes with ligands containing the triethoxysilyl group, were anchored to silica and modified USY-zeolite. These complexes have been characterized by spectroscopic and analytical techniques. The complexes anchored to the zeolite, which contains profuse supermicropores, show a higher activity for alkene hydrogenation and produce a remarkable increase of enantioselectivity ( > 95%) in the hydrogen ation of ethyl (Z)-α-benzoylaminocinnamate, taken as a model, and they represent a truly heterogeneous counterpart of the homogeneous organometallic catalysts.
Journal of Organometallic Chemistry.
