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A series of ferrocenylphosphine-stabilized rhodium nanoparticles has been prepared in one pot from the organometallic [Rh(η3-C3H5)3] precursor. This complex has been decomposed by hydrogen treatment (3 bar) in dichloromethane in the presence of five different ferrocene-based phosphine ligands. Very small rhodium nanoparticles in the size range of 1.1–1.7 nm have been obtained. These nanoparticles have shown activity in a model catalytic reaction, namely the hydrogenation of styrene. These results evidence that the metal surface is not blocked despite the steric bulk of the stabilizing ligands. Moreover, certain selectivity has been observed depending on the ligand employed. To the best of our knowledge, such a type of compound has not yet been used for stabilizing metal nanoparticles and our findings highlight the interest to do so. [ABSTRACT FROM AUTHOR]

A porous Ru nanomaterial exhibits high electrocatalytic performance and excellent durability for the hydrogen evolution reaction (HER) under both acidic and neutral conditions. It displays a low overpotential of 83 mV at a current density of 10 mA cm−2 and an excellent durability up to 12 h in 0.5 M H2SO4. [ABSTRACT FROM AUTHOR]

The solution synthesis of rhodium nanoparticles (Rh NPs) was achieved from the organometallic complex [Rh(η3-C3H5)3] under mild reaction conditions in the presence of a polymer (PVP), a monophosphine (PPh3) and a diphosphine (dppb) as a stabilizer, leading to very small Rh NPs of 2.2, 1.3 and 1.7 nm mean size, with PVP, PPh3 and dppb, respectively. The surface properties of these nanoparticles were compared using a model catalysis reaction namely, hydrogenation of cyclohexene, first under colloidal conditions and then under supported conditions after their immobilization onto an amino functionalized silica-coated magnetite support. PVP-stabilized Rh NPs were the most active catalyst whatever the catalytic conditions as a result of a strong coordination of the phosphine ligands at the metal surface that blocks some surface atoms even after several recycles of the supported nanocatalysts and limit the reactivity of the metallic surface. [ABSTRACT FROM AUTHOR]

The synthesis and catalytic activity of long-chain NHC-stabilized RuNPs are presented. Full characterization of these novel nanostructures including surface state studies show that the ligand influences the number and the location of Ru active sites which impacts the NP catalytic activity, especially in hydrogenation reactions. The high stability and versatility of these nanosystems make them successful catalysts for both oxidation and hydrogenation reactions that can even be performed successively in a one pot-fashion. [ABSTRACT FROM AUTHOR]

The betaine adduct of N-heterocyclic carbene and carbodiimide (ICy·(p-tol)NCN) was found to be a very efficient ligand to prepare very small (1–1.3 nm) ruthenium nanoparticles (RuNPs). The coordination of the ligand on the metal surface takes place through the carbodiimide moiety. The resulting RuNPs led to decarbonylation of THF and showed size selectivity for styrene hydrogenation. [ABSTRACT FROM AUTHOR]

Structural and spectroscopic properties of tetranuclear ruthenium hydrido clusters, and to a less extent, of hexanuclear ruthenium hydrido clusters, are investigated theoretically. Some of these (H)nRuk(L)m (k = 4, 6) clusters were experimentally synthesized and characterized. Non-existing structures are also considered in order to examine the role of ligands on their structure, vibrational spectra and 1HNMR chemical shifts. The calculated properties are found in very good agreement with experimental data, when available. Beyond the intrinsic interest elicited by transition metal clusters, these compounds are also considered in this paper as relevant to diamagnetic ruthenium nanoparticles as well as building blocks of hcp surfaces, which is the ruthenium nanoparticle lattice. On the basis of the very good agreement between experiments and theory, the structural and spectroscopic properties of several model clusters are also predicted in order to bring additional data which may help to analyze the spectral signature of ruthenium nanoparticles. A particular emphasis is put on 1H NMR, which is of high practical importance for characterizing the presence of hydrides in ruthenium clusters and nanoparticles. Several topics are discussed: the structural preference of surface hydrides for terminal-, edge-bridging or face-capping coordination modes, hydrides adsorption energies, the possible presence of interstitial hydrogen atoms, the dependence of 1H chemical shifts on ligands and on electron counting. [ABSTRACT FROM AUTHOR]

Review: 74 refs. [ABSTRACT FROM AUTHOR]

Here we report on the organometallic synthesis of polyvinylpyrrolidone (PVP)-stabilized palladium-rhodium nanostructures that display high electrochemical properties when used as carbon-supported electrodes (Pd x Rh 1-x -PVP/C) for methanol oxidation reaction (MOR). These nanostructures were synthesized by hydrogenation of the tris(dibenzylideneacetone)dipalladium(0) (Pd 2 (dba) 3) and tris(allyl) rhodium (Rh(η3-C 3 H 5) 3) complexes, in tetrahydrofuran (THF) under mild reaction conditions (room temperature and 3 bar H 2) and in the presence of PVP as stabilizer. The influence of methanol concentration (0.5, 1.0 and 2.0 M) as well as different scan rates (5–100 mV s−1) was evaluated to determine changes in the stability and catalytic activity. The organometallic approach and the use of PVP for the preparation of PdRh electrode materials promoted the formation of highly dispersed nanostructures, that led to a remarkably enhanced methanol electro-oxidation in alkaline medium. This high catalytic behavior can reasonably arise from a synergistic effect between Pd and Rh metals as, under the applied conditions, Rh is expected to enhance the Pd ability to oxidize methanol to CO 2 (oxophilic character) as well as the catalyst stability. From all the evaluated electrode materials, Pd 8 Rh 2 -PVP/C electrode showed the highest mass activity at high methanol concentration (2.0 M) and low scan rate (10 mV s−1). This catalyst showed a performance up to 26 times higher than that of Pd-PVP/C and interestingly an electroactivity superior to that of previously reported PdRh catalysts. [Display omitted] • This synthesis led to the formation of well-dispersed nanostructures of size <5 nm. • Pd 8 Rh 2 -PVP/C showed an enhanced performance, up to 26 times higher than Pd-PVP/C. • CVs shifts in the oxidation peak potential towards (-) values as Rh amount increases. • Oxophilic character in the PdRh alloys is favored at low Rh quantities. [ABSTRACT FROM AUTHOR]

Supported Pd nanocatalysts were prepared by deposition of Pd nanoparticles (NPs) onto spherical mesoporous carbon beads (MB) functionalized by thermal or acidic treatement. The Pd NPs were synthesized by decomposition of [Pd 2 (dba) 3 ] (dba: dibenzylideneacetone) under dihydrogen either directly on the carbon supports without stabilizer leading to naked Pd NPs (Pd/MB series) or in solution in the presence of a stabilizer (polymer (PVP series) or triphenylphosphine (TPP series)) to obtain stable colloidal solutions that were further used to impregnate the carbon materials to have carbon-deposited Pd NPs. The NPs deposited on carbon displayed a Pd loading from 0.5 to 14.8 wt.% and were characterized by different techniques (nitrogen physisorption at 77 K, H 2 -chemissorption and TPD, XRD, XPS and HRTEM). Their catalytic performance in deoxygenation of oleic acid was evaluated in batch and flow reaction conditions. Flow conditions led to superior results compared to batch. No aromatic compounds were detected as side products, but in the case of the Pd/MB series, octadecanol and octadecane were significantly formed suggesting the involvement of a deoxygenation mechanism in which the hydrocarbons were produced via both decarbonylation/decarboxylation and dehydration steps. Further experiments carried out in H 2 /N 2 mixture or in pure N 2 highlighted the key role of hydrogen. For a N 2 /H 2 of 2.5:1 the dehydration route was crossing out and even no traces of octadecanol nor octadecane were detected. Then, complete removal of H 2 produced heptadecene in a high excess compared to heptadecane (almost 7–1) thus suggesting the decarbonylation/decarboxylation steps as the main route. ICP-OES measurements indicated no leaching of palladium and simple washing of catalysts with mesitylene allowed recycling without any change in conversion or product distribution. [ABSTRACT FROM AUTHOR]

Abstract: Both (Ni, Pt) and bimetallic (Ni x Pt; x =1, 2, 3) nanoparticles have been synthesized by hydrogenation of Ni(cod)2 ad Pt2(dba)3 in the presence of a weak coordinating ligand, hexadecylamine (CH3(CH2)15NH2, HDA). These nanostructures were characterized by different techniques (Fourier Transform-Infrared Spectroscopy (FT-IR), High-Resolution Transmission Electron Microscopy (HRTEM)), and were evaluated as Hydrogen Evolution Reaction electrocatalysts in 0.5M sulfuric acid. The effects of varying the platinum amount during the synthesis were systematically studied by Cyclic Voltammetry (CV), polarization measurements and electrochemical impedance spectroscopy (EIS) techniques. HRTEM shows that the bimetallic nanostructures display a different morphology compared to that observed for pure Ni and Pt ones. The process of hydrogen adsorption–desorption in the as-prepared electrodes seems to occur in (110) and (100) facets. It was found that the increase in the activity for the HER is due to an increased electrochemical active surface area (ECSA) and/or stabilization in the case of elemental electrode materials; and to the effect of Pt amount in the case of the Ni–Pt nanostructures (synergistic effect leads to lower overpotential). It has been established that the main pathway for the HER is Volmer–Heyrovsky. [Copyright &y& Elsevier]

Colloidal metal nanoparticles exhibit interesting catalytic properties for the hydrogenation of (hetero)arenes. Catalysts based on precious metals, such as Ru and Rh, promote this reaction efficiently under mild reaction conditions. In contrast, heterogeneous catalysts based on earth-abundant metals can selectively hydrogenate (hetero)arenes but require harsher reaction conditions. Bimetallic catalysts that combine precious and earth-abundant metals are interesting materials to mitigate the drawbacks of each component. To this end, RuNi nanoparticles bearing a phosphine ligand were prepared through the decomposition of [Ru(η 4 -C 8 H 12 )(η 6 -C 8 H 10 )] and [Ni(η 4 -C 8 H 12 ) 2 ] by H 2 at 85 °C. Wide angle X-ray scattering confirmed a bimetallic segregated structure, with Ni predominantly on the surface. Spectroscopic analyses revealed that the phosphine ligand coordinated to the surface of both metals, suggesting, as well, a partial Ni shell covering the Ru core. The RuNi-based nanomaterials were used as catalysts in the hydrogenation of quinoline to assess the impact of the metallic composition and of the stabilizing agent on their catalytic performance., (© 2024 The Author(s). ChemPlusChem published by Wiley-VCH GmbH.)

Background: The effects of climate change, loss of pastureland to other land usage and presence of large carnivores are the main reasons for the increase in supplementary feeding of semi-domesticated reindeer (Rangifer tarandus tarandus) in Fennoscandia over the last decades. Feeding might expose reindeer to stress and increased animal-to-animal contact, leading to an increased risk of infectious disease transmission, such as infectious keratoconjunctivitis (IKC). As it can develop rapidly and be very painful, IKC is described as an important animal welfare concern and a potential source of economic loss. The aim of this study was to investigate the current presence of IKC and potential associations between IKC and supplementary feeding through an online questionnaire survey, distributed among reindeer herders in Norway and Sweden in 2021., Results: Seventy-six reindeer herders (33 from Norway and 43 from Sweden) responded to the questionnaire, representing 6% and 4% of the registered reindeer herding groups in Norway and Sweden, respectively. Infectious keratoconjunctivitis was common, with 54 (71%) of the 76 herders that responded having observed clinical signs during the past 10 years. These signs were mainly observed as increased lacrimation, causing "wet cheeks", but also as keratitis and conjunctivitis. Autumn and winter were the seasons in which IKC was observed most. The herders reported several measures, such as slaughter and isolation of affected reindeer, to counteract the spread of disease. The herding year 2019/2020 was associated with reports of outbreaks of IKC in herds as well as being the herding year where most herders (80%) had performed supplementary feeding. A significant association was found between IKC and feeding performed in an enclosure (odds ratio = 15.20), while feeding on free-range areas had a non-significant, negative, relationship with the appearance of IKC outbreaks (odds ratio = 0.29). Finally, there was a trend in the data suggesting that IKC affected calves especially., Conclusions: Infectious keratoconjunctivitis is a common disease, mainly observed in winter and autumn. It usually has mild to moderately severe clinical signs. Our results imply that IKC is associated with stress and feeding situations and that calves might be more susceptible than adults, however, this needs to be confirmed with further studies, preferably at an individual animal level., (© 2023. The Author(s).)

A series of ruthenium nanoparticles (RuNPs) were synthesized by the organometallic approach in different functionalized imidazolium ionic liquids (FILs). Transmission electron microscopy (TEM) showed well-dispersed and narrow-sized RuNPs ranging from 1.3 to 2.2 nm, depending on the IL functionalization. Thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) allowed the interaction between the RuNPs and the ILs to be studied. The RuNPs stabilized by methoxy-based FILs (MEM and MME) displayed a good balance between catalytic activity and stability when evaluated in the hydrogenation of styrene (S) under mild reaction conditions. Moreover, the catalysts showed total selectivity towards ethylbenzene (EB) under milder reaction conditions (5 bar, 30 °C) than reported in the literature for other RuNP catalysts.

Carbon dioxide (CO 2) is the most important greenhouse gas (GHG), accounting for 76% of all GHG emissions. The atmospheric CO 2 concentration has increased from 280 ppm in the pre-industrial era to about 418 ppm, and is projected to reach 570 ppm by the end of the 21 st century. In addition to reducing CO 2 emissions from anthropogenic activities, strategies to adequately address climate change must include CO 2 capture. To promote circular economy, captured CO 2 should be converted to value-added materials such as fuels and other chemical feedstock. Due to their tunable chemistry (which allows them to be selective) and high surface area (which allows them to be efficient), engineered nanomaterials are promising for CO 2 capturing and/or transformation. This work critically reviewed the application of nanomaterials for the transformation of CO 2 into various fuels, like formic acid, carbon monoxide, methanol, and ethanol. We discussed the literature on the use of metal-based nanomaterials, inorganic/organic nanocomposites, as well as other routes suitable for CO 2 conversion such as the electrochemical, non-thermal plasma, and hydrogenation routes. The characteristics, steps, mechanisms, and challenges associated with the different transformation technologies were also discussed. Finally, we presented a section on the outlook of the field, which includes recommendations for how to continue to advance the use of nanotechnology for conversion of CO 2 to fuels., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The conversion of biomass as a sustainable path to access valuable chemicals and fuels is very attractive for the chemical industry, but catalytic conversions still often rely on the use of noble metals. Sustainability constraints require developing alternative catalysts from abundant and low-cost metals. In this context, NiFe nanoparticles are interesting candidates. In their reduced and supported form, they have been reported to be more active and selective than monometallic Ni in the hydrogenation of the polar functions of organic molecules, and the two metals are very abundant. However, unlike noble metals, Ni and Fe are easily oxidized in ambient conditions, and understanding their transformation in both oxidative and reductive atmospheres is an important though seldom investigated issue to be addressed before their application in catalysis. Three types of NiFe nanoparticles were prepared by an organometallic approach to ensure the formation of ultrasmall nanoparticles (<3.5 nm) with a narrow size distribution, controlled composition and chemical order, while working in mild conditions: Ni2Fe1 and Ni1Fe1, both with a Ni rich core and Fe rich surface, and an alloy with a Ni1Fe9 composition. Supported systems were obtained by the impregnation of silica with a colloidal solution of the preformed nanoparticles. Using advanced characterization techniques, such as wide-angle X-ray scattering (WAXS) and X-ray absorption spectroscopy (XAS) in in situ conditions, this study reports on the evolution of the chemical order and of the oxidation state of the metals upon exposure to air, hydrogen, and/or increasing temperature, all factors that may affect their degree of reduction and subsequent performance in catalysis. We show that if oxidation readily occurs upon exposure to air, the metals can revert to their initial state upon heating in the presence of H 2 but with a change in structure and chemical ordering.

Production of hydrogen from a renewable source that is water requires the development of sustainable catalytic processes. This implies, among others, developing efficient catalytic materials from abundant and low-cost resources and investigating their performance, especially in the oxidation of water as this half-reaction is the bottleneck of the water splitting process. For this purpose, NiFe-based nanoparticles with sizes ca . 3-4 nm have been synthesized by an organometallic approach and characterized by complementary techniques (WAXS, TEM, STEM-HAADF, EDX, XPS, and ATR-FTIR). They display a Ni core and a mixed Ni-Fe oxide shell. Once deposited onto FTO electrodes, they have been assessed in the electrocatalytic oxygen evolution reaction under alkaline conditions. Three different Ni/Fe ratios (2/1, 1/1 and 1/9) have been studied in comparison with their monometallic counterparts. The Ni2Fe1 nanocatalyst displayed the lowest overpotential (320 mV at j = 10 mA cm -2 ) as well as excellent stability over 16 h.

Exploiting biomass to synthesise compounds that may replace fossil-based ones is of high interest in order to reduce dependence on non-renewable resources. 1,2-pentanediol and 1,5-pentanediol can be produced from furfural, furfuryl alcohol or tetrahydrofurfuryl alcohol following a metal catalysed hydrogenation/C-O cleavage procedure. Colloidal ruthenium nanoparticles stabilized with polyvinylpyrrolidone in situ modified with different organic compounds are able to produce 1,2-pentanediol directly from furfural in a 36% of selectivity at 125 °C under 20 bar of H 2 pressure.

The present environmental crisis prompts the search for renewable energy sources such as solar-driven production of hydrogen from water. Herein, we report an efficient hybrid photocatalyst for water oxidation, consisting of a ruthenium polypyridyl complex covalently grafted on core/shell Fe@FeO x nanoparticles via a phosphonic acid group. The photoelectrochemical measurements were performed under 1 sun illumination in 1 M KOH. The photocurrent density of this hybrid photoanode reached 20 μA/cm 2 (applied potential of +1.0 V vs reversible hydrogen electrode), corresponding to a turnover frequency of 0.02 s -1 . This performance represents a 9-fold enhancement of that achieved with a mixture of Fe@FeO x nanoparticles and a linker-free ruthenium polypyridyl photosensitizer. This increase in performance could be attributed to a more efficient electron transfer between the ruthenium photosensitizer and the Fe@FeO x catalyst as a consequence of the covalent link between these two species through the phosphonate pendant group.

To shed light on the factors governing the stability and surface properties of iron nanoparticles, a series of iron nanoparticles has been produced by hydrogenation of two different iron amido complexes: the bis[bis(trimethylsilyl)amido] Fe(ii), [Fe(N(SiMe 3 ) 2 ) 2 ] 2 , and the bis(diphenylamido) Fe(ii), [Fe(NPh 2 ) 2 ]. Nanostructured materials of bcc structure, or nanoparticles displaying average sizes below 3 nm and a polytetrahedral structure, have been obtained. Depending on the synthesis conditions, the magnetization of the nanoparticles was either significantly lower than that of bulk iron, or much higher as for clusters elaborated under high vacuum conditions. Unexpectedly, hydrogenation of aromatic groups of the ligands of the [Fe(NPh 2 ) 2 ] precursor has been observed in some cases. Confrontation of the experimental results with DFT calculations made on polytetrahedral Fe 91 model clusters bearing hydrides, amido and/or amine ligands at their surface, has shown that amido ligands can play a key role in the stabilisation of the nanoparticles in solution while the hydride surface coverage governs their surface magnetic properties. This study indicates that magnetic measurements give valuable indicators of the surface properties of iron nanoparticles in this size range, and beyond, of their potential reactivity., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Production of formate via CO2/bicarbonate hydrogenation using cheap metal-based heterogeneous catalysts is attractive. Herein, we report the organometallic synthesis of a foam-like Ni@Ni(OH)2 composite nanomaterial which exhibited remarkable air stability and over 2 times higher catalytic activity than commercial RANEY® Ni catalyst in formate synthesis. Formate generation was achieved with an optimal rate of 6.0 mmol gcat-1 h-1 at 100 °C, a significantly lower operation temperature compared to the 200-260 °C reported in the literature. Deep characterization evidenced that this nanomaterial was made of an amorphous Ni(OH)2 phase covering metallic Ni sites; a core-shell structure which is crucial for the stability of the catalyst. The adsorption of bicarbonates onto the Ni@Ni(OH)2 catalyst was found to be a kinetically relevant step in the reaction, and the Ni-Ni(OH)2 interface was found to be beneficial for both CO2 and H2 activation thanks to a cooperative effect. Our findings emphasize the underestimated potential of Ni-based catalysts in CO2 hydrogenation to formate, indicating a viable strategy to develop stable, cheap metal catalysts for greener catalytic applications.

Rhodium nanoparticles (Rh NPs) embedded in different amphiphilic core-crosslinked micelle (CCM) latexes (RhNP@CCM) have been synthesized by [RhCl(COD)(TPP@CCM)] reduction with H 2 (TPP@CCM = core-anchored triphenylphosphine). The reduction rate depends on temperature, on the presence of base (NEt 3 ) and on the P/Rh ratio. For CCMs with outer shells made of neutral P(MAA- co -PEOMA) copolymer chains (RhNP@CCM-N), the core-generated Rh NPs tend to migrate toward the hydrophilic shell and to agglomerate depending on the P/Rh ratio and core TPP density, whereas the MAA protonation state has a negligible effect. Conversely, CCMs with outer shells made of polycationic P(4VPMe + I - ) chains (RhNP@CCM-C) maintain core-confined and well dispersed Rh NPs. All RhNP@CCMs were used as catalytic nanoreactors under aqueous biphasic conditions for acetophenone, styrene and 1-octene hydrogenation. Styrene was efficiently hydrogenated by all systems with high selectivity for vinyl reduction. For acetophenone, competition between benzene ring and carbonyl reduction was observed as well as a limited access to the catalytic sites when using CCM-C. Neat 1-octene was also converted, but the activity increased when the substrate was diluted in 1-nonanol, which is a better core-swelling solvent. Whereas the molecular Rh I center was more active than the Rh 0 NPs in 1-octene hydrogenation, the opposite trend was observed for styrene hydrogenation. Although Rh NP migration and agglomeration occurred for RhNP@CCM-N, even at high P/Rh, the NPs remained core-confined for RhNP@CCM-C, but only when toluene rather than diethyl ether was used for product extraction before recycling., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)