Size-controllable APTS stabilized ruthenium(0) nanoparticles catalyst for the dehydrogenation of dimethylamine-borane at room temperature

Dimethylamine-borane, (CH(3))(2)NHBH(3), has been considered as one of the attractive materials for the efficient storage of hydrogen, which is still one of the key issues in the "Hydrogen Economy". In a recent communication we have reported the synthesis and characterization of 3-aminopropyltriethoxysilane stabilized ruthenium(0) nanoparticles with the preliminary results for their catalytic performance in the dehydrogenation of dimethylamine-borane at room temperature. Herein, we report a complete work including (i) effect of initial [APTS]/[Ru] molar ratio on both the size and the catalytic activity of ruthenium(0) nanoparticles, (ii) collection of extensive kinetic data under non-MTL conditions depending on the substrate and catalyst concentrations to define the rate law of Ru(0)/APTS-catalyzed dehydrogenation of dimethylamine-borane at room temperature, (iii) determination of activation parameters (E(a), ΔH(#) and ΔS(#)) for Ru(0)/APTS-catalyzed dehydrogenation of dimethylamine-borane; (iv) demonstration of the catalytic lifetime of Ru(0)/APTS nanoparticles in the dehydrogenation of dimethylamine-borane at room temperature, (v) testing the bottlability and reusability of Ru(0)/APTS nanocatalyst in the room-temperature dehydrogenation of dimethylamine-borane, (vi) quantitative carbon disulfide (CS(2)) poisoning experiments to find a corrected TTO and TOF values on a per-active-ruthenium-atom basis, (vii) a summary of extensive literature review for the catalysts tested in the catalytic dehydrogenation of dimethylamine-borane as part of the results and discussions.     

Rhodium(I) catalyst supported on polymer crystal surfaces: Further hydrogenation studies

Catalysts bound to polymers in the form of crosslinked beads have been demonstrated to have a number of advantages over homogeneous catalysts. However, there are several problems that exist due to the polymer support being in the form of a bead. The rate of reaction depends on the presence of solvents that adequately swell the bead in order to allow access to the catalytic sites. Differences in polarity and reactant size can inhibit diffusion into the bead. Recently a new system has been developed whereby tris(triphenyl phosphine) chlororhodium (I) (Wilkinson's catalyst) is bound to the surface of polyethylene single crystals. Polyethylene single crystals have a very high surface to volume ratio allowing for greater ease of reaction compared to a bead system. In a previous paper we showed that there is a dramatic increase in catalytic activity and that the reaction rate increased as the polarity of solvent was increased, even in ethanol where the homogeneous catalyst is not soluble and the polystyrene bead support would not swell. In this letter we are describing the activity of hydrogenation of olefins contained in both large and/or polar molecules. The results demonstrate the advantages of supported catalysts on polyethylene single crystals rather than on polymer beads.     

Facile synthesis of bis(indolyl)methanes using catalytic amount of iodine at room temperature under solvent-free conditions

Efficient electrophilic substitution reactions of indoles with various aromatic aldehydes were carried out using a catalytic amount of I₂ under solvent-free conditions to afford the corresponding bis(indolyl)methanes in excellent yields.     

Silica supported perchloric acid (HClO4-SiO2): a green,reusable, and highly efficient heterogeneous catalyst for the synthesis of thioethers under solvent-free conditions at room temperature

Abstract

A highly efficient and clean procedure is described for the synthesis of thioethers with excellent yields under solvent-free conditions at room temperature using a catalytic amount of HClO₄-SiO₂. The catalyst is easily prepared, stable, and reusable without much loss of catalytic activity, and is efficient under the reaction conditions.     

Cellulose sulfuric acid: reusable catalyst for solvent-free synthesis of bis(indolyl)methanes at room temperature

Abstract

Bis(indolyl)methanes were synthesized from indole and aldehydes under solvent-free conditions using cellulose sulfuric acid (CSA) as a catalyst at room temperature. CSA is easily prepared and it was also found that this catalyst could be recovered quantitatively and reused without much loss of catalytic activity.     

Superior (de)hydrogenation properties of Mg-Ti-Pd trilayer films at room temperature

In this paper, a series of Mg-Ti-Pd trilayer films with various thicknesses of the Ti interlayer were prepared by magnetron sputtering. The trilayer films could be reversibly (de)hydrogenated at room temperature. The relationship between structure and properties of Mg-Ti-Pd trilayer films was comprehensively investigated. Our studies showed that the hydrogen storage properties of Mg-Pd films were significantly improved with the addition of a Ti interlayer. The optimal hydrogenation properties were obtained when the Ti interlayer was 1 nm. The superior hydrogenation properties achieved by introduction of the Ti interlayer could be attributed to several aspects: prevention of Mg-Pd alloying; catalytic dissociation of H(2) molecules and provision of heterogeneous nucleation sites. These results were elucidative for the development of high performance intermetallic hydrogen storage materials and thin film based functional devices.     

Silver nanoparticles supported on ionic‐tagged magnetic hydroxyapatite as a highly efficient and reusable nanocatalyst for hydrogenation of nitroarenes in water

A novel chemically modified magnetic hydroxyapatite (MHAp) was prepared and used as support and stabilizer for the synthesis of silver nanoparticles. First, 1,4‐diazabicyclo[2.2.2]octane (DABCO) was successfully grafted onto the surface of MHAp, and then silver nanoparticles were homogeneously loaded on mesoporous MHAp‐DABCO (ionic‐tagged MHAp) nanocomposite by in situ chemical reduction of silver nitrate using sodium borohydride. The structure and properties of the resulting MHAp‐DABCO‐Ag nanocomposite were confirmed using various techniques. The catalytic activity of ionic‐tagged MHAp‐Ag nanocatalyst was investigated for the hydrogenation reaction of nitroarenes in aqueous media. The results reveal that the Ag‐containing inorganic–organic nanocomposite is highly efficient for the reduction of a wide range of aromatic nitro compounds under green conditions. The superparamagnetic nature of the nanocatalyst leads to its being readily removed from solution via application of a magnetic field, and it can be easily stored and reused.     

Poly(vinyl)chloride supported palladium nanoparticles: catalyst for rapid hydrogenation reactions

Palladium nanoparticles supported over poly(vinyl)chloride matrix (PVC-Pd(0)) are prepared through an efficient and inexpensive protocol. The catalyst has been characterized by XRD, SEM and TEM and its utility for the reduction of a range of functional groups as well as for the removal of some common protecting groups employed in peptide chemistry is demonstrated.     

Highly chemoselective reduction of azides to amines by Fe(0) nanoparticles in water at room temperature

A highly chemoselective reduction of aryl, heteroaryl, acyl and sulfonyl azides to the corresponding amines has been achieved by Fe(0) nanoparticles in water at room temperature in the absence of external hydride source. Several readily reducible functionalities including alkene, alkyne, S-S linkage, OTBDMS remain unaffected during reduction.     

钌(II)-吡啶基NNN配合物催化酮的室温(不对称)氢转移反应

合成了一种基于吡啶骨架含有苯并咪唑和手性咪唑啉基团的三齿NNN配体及其二价钌(II)配合物,通过核磁共振波谱学和X射线单晶晶体结构测定确认了钌(II)配合物的分子结构.这些配合物在室温下催化酮的氢转移反应,表现出了优异的催化活性,收率和ee值最高分别可达99%和97%.     

Copper(0)-mediated radical polymerization of styrene at room temperature

The “living’/controlled radical polymerization (LRP) of styrene (St) at room temperature is rarely reported. In this work, copper(0) (Cu(0))-mediated radical polymerization of St at room temperature was investigated in detail. Dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF) as well as a binary solvent, tetrahydrofuran/1,1,1,3,3,3-hexafluoro-2-propanol were used as the solvents, respectively. Methyl-2-bromopropionate and ethyl 2-bromoisobutyrate were used as the initiators, respectively. The polymerization proceeded smoothly with moderate conversions at room temperature. It was found that DMF was a good solvent with the essential features of LRP, while DMSO was a poor solvent with uncontrollable molecular weights. Besides, the match among the initiator, solvent and molar ratios of reactants can modulate the livingness of the polymerization, and the proper selection of ligand was also crucial to a controlled process. This work provided a first example of Cu(0)-mediated radical polymerization of St at room temperature, which would enrich and strength the LRP technique.     

Zinc(II) perchlorate as a new and highly efficient catalyst for formation of aldehyde 1,1-diacetate at room temperature and under solvent-free conditions

Zinc(II) perchlorate efficiently catalysed the conversion of aromatic, heteroaromatic, and aliphatic aldehydes to 1,1-diacetates under solvent-free conditions at room temperature. It was compatible with other functional groups (e.g., ether, ester, nitro, and cyano) likely to interfere by complex formation with the catalyst. Other anhydrides such as isobutyric, pivalic, and benzoic anhydrides afforded the corresponding 1,1-dicarboxylates and established the generality. The reaction rate was influenced by the steric and electronic nature of the anhydride. The rate of 1,1-dicarboxylate formation was found to follow the order Ac₂O > (i-PrCO)₂O > (t-BuCO)₂O > (PhCO)₂O and no 1,1-dicarboxylate formation took place with (ClCH₂CO)₂O, and (F₃CO)₂O. During inter- and intra-molecular competition between a ketone and an aldehyde group with Ac₂O, 1,1-diacetate formation took place exclusively with the aldehyde group. An 88:12 selectivity was observed for 1,1-diacetate formation in favour of 1-naphthaldehyde during competition with 2-methoxy-1-naphthaldehyde.     

Pd nanoparticles supported on CeO2 as efficient catalyst for hydrogen generation from formaldehyde solution at room temperature

A facile and efficient method for facilitating hydrogen generation from formaldehyde aqueous solution was developed using Pd nanoparticles supported on CeO₂ (Pd/CeO₂) as the catalyst. The prepared Pd/CeO₂ catalyst exhibited 100% H₂ selectivity and excellent catalytic activity for formaldehyde dehydrogenation with the initial rate of 2089 ml min⁻¹ g_Pd⁻¹ at room temperature and atmospheric pressure without any extra additive. The prepared catalyst was stable and reusable, and its catalytic activity kept almost unchanged after it was reused for the fifth run. Therefore, it is considered that this Pd/CeO₂ based hydrogen generation system may serve as an alternative hydrogen supply candidate for practical application.     

Copper(II) tetrafluoroborate as a novel and highly efficient catalyst for N-tert-butoxycarbonylation of amines under solvent-free conditions at room temperature

Commercially available copper(II) tetrafluoroborate hydrate was found to be a highly efficient catalyst for chemoselective N-tert-butoxycarbonylation of amines with di-tert-butyl dicarbonate under solvent-free conditions and at room temperature. Various aromatic amines were protected as their N-tert-butyl carbamates in high yields and in short times. No competitive side reactions such as isocyanate, urea, and N,N-di-t-Boc formation was observed. Chemoselective N-tert-butoxycarbonylation was achieved with substrates bearing OH and SH groups. Chiral α-amino acid esters afforded the corresponding N-t-Boc derivatives in excellent yields.     

硫存在下Beta沸石负载钯催化剂上的芳烃加氢性能研究

采用浸渍和离子交换方法，制备了一系列H-Beta沸石负载钯催化剂，并用XRD，N2吸附和氨程序升温脱附进行了表征。采用连续流动固定床反应器，在总压4 MPa，270 ℃，液体空速为16 h－1和硫的质量分数为100×10－6的条件下进行了四氢萘的加氢反应。实验结果表明，钯催化剂的催化性能与催化剂制备方法及载体的硅铝比有关系。对Pd/Beta25(25是硅铝比，下同)来说,离子交换(IE)催化剂的加氢活性高于对应的初湿浸渍(IWI)样品。对于所有离子交换催化剂，Pd/Beta80(IE)在整个反应期间催化活性及抗硫性最好。Pd/Beta25(IE)四氢萘的初始转化率高达77％，失活最快，8 h降到10％；Pd/Beta60(IE)初始转化率为60％，8 h后为16％；Beta80负载催化剂最稳定，起始和8 h后转化率分别为75％和55％。离子交换的Beta80负载Pd催化剂的优良催化活性可以归结为催化剂中有较高比例的中强和强酸性位的存在，尤其中强酸比例较高，同时较多中孔的存在也是其中的影响因素之一。少量Al2O3的添加可以改善催化剂的活性。     

Stabilized rhodium(0) nanoparticles: a reusable hydrogenation catalyst for arene derivatives in a biphasic water-liquid system

A colloidal system based on an aqueous suspension of rhodium(o) nanoparticles proved to be an efficient catalyst for the hydrogenation of arene derivatives under biphasic conditions. The rhodium nanoparticles (2-2.5 nm) were synthesized by the reduction of RhCl3 x 3H2O with sodium borohydride and were stabilized by highly water-soluble N-alkyl-N-(2-hydroxyethyl)ammonium salts (HEA-Cn). These surfactant molecules were characterized by measurements of the surface tension and the aqueous dispersions with rhodium were observed by transmission electron cryomicroscopy. The catalytic system is efficient under ultramild conditions, namely room temperature and 1 atm H2 pressure. The aqueous phase which contains the protected rhodium(0) colloids can be reused without significant loss of activity. The microheterogeneous behavior of this catalytic system was confirmed on a mercury poisoning experiment.     

Iridium(0) nanocluster, acid-assisted catalysis of neat acetone hydrogenation at room temperature: exceptional activity, catalyst lifetime, and selectivity at complete conversion

Acetone hydrogenation catalysis is important in applications such as heat pumps and fuel cells or in fulfilling the sizable demand for the product of selective acetone hydrogenation, 2-propanol. Reported herein is the discovery of a superior acetone hydrogenation catalyst--superior in terms of activity at low temperature, selectivity at complete conversion, and total catalyst lifetime. The new catalyst system consists of Ir(0)(n) nanoclusters plus HCl easily and reproducibly formed from commercially available [(1,5-COD)IrCl](2) under H(2). The resultant, room temperature, high activity, and highly selective (2/n)Ir(0)(n) plus 2HCl catalyst system hydrogenates acetone at 22 degrees C and 40 psig of H(2) pressure to 95% 2-propanol and the rest diisopropyl ether at 100% conversion with 16400 total catalytic turnovers and with an initial turnover frequency of 1.9 s(-1) at 22 degrees C. When molecular sieves are added, the catalyst system becomes even more selective and long-lived, providing the complete and selective conversion of acetone to 100% 2-propanol with 188000 total turnovers. Also reported are initial kinetic, D-labeling and other mechanistic studies, a summary section detailing the four main findings, the "green chemistry" aspects, and the current main drawback (a limited catalytic lifetime due to nanocluster precipitation) of the present invention. A review of the extensive literature of acetone hydrogenation is also tabulated as part of the Supporting Information.