Lignin First: Confirming the Role of the Metal Catalyst in Reductive Fractionation.

Rhodium nanoparticles embedded on the interior of hollow porous carbon nanospheres, able to sieve monomers from polymers, were used to confirm the precise role of metal catalysts in the reductive catalytic fractionation of lignin. The study provides clear evidence that the primary function of the metal catalyst is to hydrogenate monomeric lignin fragments into more stable forms following a solvent-based fractionation and fragmentation of lignin.

Towards Hydrogen Storage through an Efficient Ruthenium-Catalyzed Dehydrogenation of Formic Acid.

Hydrogen is of fundamental importance for the construction of modern clean-energy supply systems. In this context, the catalytic dehydrogenation of formic acid (FA) is a convenient method to generate H gas from an easily available liquid. One of the issues associated with current catalytic dehydrogenation systems is insufficient stability.

Versatile palladium-catalyzed double carbonylation of aryl bromides.

A versatile palladium-catalyzed double carbonylation of aryl bromides has been developed. Using Pd(OAc)/BuPAd as the catalyst system and DBU as the base, under relatively low CO pressure, various α-ketoamides were produced in good yields. In order to get insight into the reaction pathway, real time NMR studies were performed as well and a correlated reaction mechanism is been given.

Homogeneous Catalysis for Sustainable Hydrogen Storage in Formic Acid and Alcohols.

Hydrogen gas is a storable form of chemical energy that could complement intermittent renewable energy conversion. One of the main disadvantages of hydrogen gas arises from its low density, and therefore, efficient handling and storage methods are key factors that need to be addressed to realize a hydrogen-based economy. Storage systems based on liquids, in particular, formic acid and alcohols, are highly attractive hydrogen carriers as they can be made from CO or other renewable materials, they can be used in stationary power storage units such as hydrogen filling stations, and they can be used directly as transportation fuels.

Delineating the Mechanism of Ionic Liquids in the Synthesis of Quinazoline-2,4(1H,3H)-dione from 2-Aminobenzonitrile and CO.

Ionic liquids (ILs) are versatile solvents and catalysts for the synthesis of quinazoline-2,4-dione from 2-aminobenzonitrile and CO . However, the role of the IL in this reaction is poorly understood. Consequently, we investigated this reaction and showed that the IL cation does not play a significant role in the activation of the substrates, and instead plays a secondary role in controlling the physical properties of the IL.

CO as a hydrogen vector - transition metal diamine catalysts for selective HCOOH dehydrogenation.

The homogeneous catalytic dehydrogenation of formic acid in aqueous solution provides an efficient in situ method for hydrogen production, under mild conditions, and at an adjustable rate. We synthesized a series of catalysts with the chemical formula [(Cp*)M(N-N')Cl] (M = Ir, Rh; Cp* = pentamethylcyclopentadienyl; N-N = bidentate chelating nitrogen donor ligands), which have been proven to be active in selective formic acid decomposition in aqueous media. The scope of the study was to examine the relationship between stability and activity of catalysts for formic acid dehydrogenation versus electronic and steric properties of selected ligands, following a bottom-up approach by increasing the complexity of the N,N'-ligands progressively.

Carbon Dioxide to Methanol: The Aqueous Catalytic Way at Room Temperature.

Carbon dioxide may constitute a source of chemicals and fuels if efficient and renewable processes are developed that directly utilize it as feedstock. Two of its reduction products are formic acid and methanol, which have also been proposed as liquid organic chemical carriers in sustainable hydrogen storage. Here we report that both the hydrogenation of carbon dioxide to formic acid and the disproportionation of formic acid into methanol can be realized at ambient temperature and in aqueous, acidic solution, with an iridium catalyst.

Calorimetric and spectroscopic studies on solvation energetics for H₂ storage in the CO₂/HCOOH system.

Solvents playing a crucial role in many chemical reactions and additives can be used to shift the reaction equilibrium. Herein we study the enthalpy of mixing for selected solvents (aqueous, organic) and basic additives (amines, aqueous KOH) when mixed with formic acid with the aim to optimize hydrogen storage/delivery in the CO2/HCOOH system. Formic acid, resulting from carbon dioxide hydrogenation, reaches highest yields when effectively "removed" from the reaction equilibrium.

Hydrogen Storage in the Carbon Dioxide - Formic Acid Cycle.

This year Mankind will release about 39 Gt carbon dioxide into the earth's atmosphere, where it acts as a greenhouse gas. The chemical transformation of carbon dioxide into useful products becomes increasingly important, as the CO(2) concentration in the atmosphere has reached 400 ppm. One approach to contribute to the decrease of this hazardous emission is to recycle CO(2), for example reducing it to formic acid.

Rh(I)-Catalyzed Hydroamidation of Olefins via Selective Activation of N-H Bonds in Aliphatic Amines.

Hydroamidation of olefins constitutes an ideal, atom-efficient method to prepare carboxylic amides from easily available olefins, CO, and amines. So far, aliphatic amines are not suitable for these transformations. Here, we present a ligand- and additive-free Rh(I) catalyst as solution to this problem.

Metal-free catalyst for the chemoselective methylation of amines using carbon dioxide as a carbon source.

N-methylation of amines is an important step in the synthesis of many pharmaceuticals and has been widely applied in the preparation of other key intermediates and chemicals. Therefore, the development of efficient methylation methods has attracted considerable attention. In this respect, carbon dioxide is an attractive C1 building block because it is an abundant, renewable, and nontoxic carbon source.

Base-free non-noble-metal-catalyzed hydrogen generation from formic acid: scope and mechanistic insights.

The iron-catalyzed dehydrogenation of formic acid has been studied both experimentally and mechanistically. The most active catalysts were generated in situ from cationic Fe(II) /Fe(III) precursors and tris[2-(diphenylphosphino)ethyl]phosphine (1, PP3 ). In contrast to most known noble-metal catalysts used for this transformation, no additional base was necessary.

Direct synthesis of formic acid from carbon dioxide by hydrogenation in acidic media.

The chemical transformation of carbon dioxide into useful products becomes increasingly important as CO2 levels in the atmosphere continue to rise as a consequence of human activities. In this article we describe the direct hydrogenation of CO2 into formic acid using a homogeneous ruthenium catalyst, in aqueous solution and in dimethyl sulphoxide (DMSO), without any additives. In water, at 40 °C, 0.

Enhanced conversion of carbohydrates to the platform chemical 5-hydroxymethylfurfural using designer ionic liquids.

5-Hydroxymethylfurfural (HMF) is a key platform chemical that may be obtained from various cellulosic (biomass) derivatives. Previously, it has been shown that ionic liquids (ILs) facilitate the catalytic conversion of glucose into HMF. Herein, we demonstrate that the careful design of the IL cation leads to new ionic solvents that enhance the transformation of glucose and more complex carbohydrates into HMF significantly.

Electrostatic and non-covalent interactions in dicationic imidazolium-sulfonium salts with mixed anions.

A series of thioether-functionalised imidazolium salts have been prepared and characterized. Subsequent reaction of the thioether-functionalised imidazolium salts with iodomethane affords imidazolium-sulfonium salts composed of doubly charged cations and two different anions. Imidazolium-sulfonium salts containing a single anion type are obtained either by a solvent extraction method or by anion exchange.

Amide bond formation via C(sp3)-H bond functionalization and CO insertion.

An efficient method for the synthesis of amides via Pd-catalyzed oxidative carbonylation of C(sp(3))-H bonds with CO and amines is described. The route efficiently provides substituted phenyl amides from alkanes.

Hydrogen storage: beyond conventional methods.

The efficient storage of hydrogen is one of three major hurdles towards a potential hydrogen economy. This report begins with conventional storage methods for hydrogen and broadly covers new technology, ranging from physical media involving solid adsorbents, to chemical materials including metal hydrides, ammonia borane and liquid precursors such as alcohols and formic acid.

How strong is hydrogen bonding in ionic liquids? Combined X-ray crystallographic, infrared/Raman spectroscopic, and density functional theory study.

Hydrogen bonding in ionic liquids based on the 1-(2'-hydroxylethyl)-3-methylimidazolium cation ([C₂OHmim](+)) and various anions ([A](-)) of differing H-bond acceptor strength, viz. hexafluorophosphate [PF6](-), tetrafluoroborate [BF₄](-), bis(trifluoromethanesulfonimide) [Tf₂N](-), trifluoromethylsulfonate [OTf](-), and trifluoroacetate [TFA](-), was studied by a range of spectroscopic and computational techniques and, in the case of [C₂OHmim][PF6], by single crystal X-ray diffraction. The first quantitative estimates of the energy (E(HB)) and the enthalpy (-ΔH(HB)) of H-bonds in bulk ILs were obtained from a theoretical analysis of the solid-state electron-density map of crystalline [C₂OHmim][PF6] and an analysis of the IR spectra in crystal and liquid samples.

Direct, in situ determination of pH and solute concentrations in formic acid dehydrogenation and CO(2) hydrogenation in pressurised aqueous solutions using (1)H and (13)C NMR spectroscopy.

In water, spin-lattice relaxation times (T(1)) and calibration curves for chemical shifts have been determined for the (13)C and the (1)H(C) atoms in HCOOH, HCOONa, CO(2), Na(2)CO(3) and NaHCO(3) by NMR spectroscopy. These data facilitate kinetic and mechanistic studies for H(2) storage/delivery in the carbon dioxide-formic acid systems under H(2) and CO(2) pressures.

Development of palladium surface-enriched heteronuclear Au-Pd nanoparticle dehalogenation catalysts in an ionic liquid.

Heteronuclear Au-Pd nanoparticles were prepared and immobilized in the functionalized ionic liquid [C(2)OHmim][NTf(2)]. The structural and electronic properties of the nanoparticles were characterized by a range of techniques and the surface of the nanoparticles was found to be enriched in Pd. Moreover, the extent of Pd enrichment is easily controlled by varying the ratio of Au and Pd salts used in the synthesis.

Classical and non-classical phosphine-Ru(II)-hydrides in aqueous solutions: many, various, and useful.

Hydrogenation of the water-soluble [{RuCl(2)(mtppms)(2)}(2)] (mtppms = monosulfonated triphenylphosphine) was studied in aqueous solutions in the presence of excess mtppms both with H(2) and with aqueous HCOONa. Depending on the reductant, the pH and H(2) pressure altogether nine hydride species were identified. In acidic solutions at 1 bar H(2) pressure the known [RuHCl(mtppms)(3)] (1) and [{RuHCl(mtppms)(2)}(2)] (3) were formed, however, elevated pressure led to the formation of trans-[RuH(2)(mtppms)(4)] (11).

Hydrogen storage and delivery: the carbon dioxide - formic acid couple.

Carbon dioxide and the carbonates, the available natural C1 sources, can be easily hydrogenated into formic acid and formates in water; the rate of this reduction strongly depends on the pH of the solution. This reaction is catalysed by ruthenium(II) pre-catalyst complexes with a large variety of water-soluble phosphine ligands; high conversions and turnover numbers have been realised. Although ruthenium(II) is predominant in these reactions, the iron(II) - tris[(2-diphenylphosphino)-ethyl]phosphine (PP3) complex is also active, showing a new perspective to use abundant and inexpensive iron-based compounds in the CO2 reduction.

Efficient dehydrogenation of formic acid using an iron catalyst.

Hydrogen is one of the essential reactants in the chemical industry, though its generation from renewable sources and storage in a safe and reversible manner remain challenging. Formic acid (HCO(2)H or FA) is a promising source and storage material in this respect. Here, we present a highly active iron catalyst system for the liberation of H(2) from FA.