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This study investigated the electronic structure of single-atom Rhodium (Rh) and Iridium (Ir) adsorbed on defective and impurity-doped ZnO(0001) surfaces, and assessed their activity towards the CO oxidation reaction. Our findings reveal that surface impurities significantly influence the binding energies and electronic properties of the metal atoms, with Al and Cr serving as particularly effective promoters. While Rh and Ir acquire a positive charge upon incorporation on the unpromoted Zn(0001) surface, adsorption directly on the promoter results in a net negative charge, thus facilitating the activation of both CO and O2 species. These results highlight the potential of impurity-promoted ZnO surfaces in modulating and tailoring the electronic properties of SACs, which can be used for a rational design of active single-atom catalysts. [ABSTRACT FROM AUTHOR]

In the context of the growing importance of heterocyclic compounds across various disciplines, numerous strategies for their construction have emerged. Exploiting the distinctive properties of cyclopropenes, this study introduces an innovative approach for the synthesis of benzo‐fused five‐membered oxa‐ and aza‐heterocycles through a formal [4+1] cyclization and subsequent acid‐catalyzed intramolecular O‐ to N‐ rearrangement. These transformations exhibit mild reaction conditions and a wide substrate scope. The applications in the late‐stage modification of complex molecules and in the synthesis of a potential PD‐L1 gene down‐regulator, make this method highly appealing in related fields. Combined experimental mechanistic studies and DFT calculations demonstrate Rh(III)‐mediated sequential C─H coupling/π‐allylation/dynamically favorable O‐attack route. [ABSTRACT FROM AUTHOR]

A facile synthesis of Pt-Rh 2 O 3 /CN x composite is reported for superior electrocatalytic hydrogen evolution and oxidation reaction (HER/HOR) in base. The HER/HOR performance of Pt-Rh 2 O 3 /CN x is ∼6/3.4 times better than commercial Pt/C. Both the hydrogen and hydroxyl binding energy are equal descriptors for alkaline HER/HOR. The hydrogen spillover from Pt to Rh 2 O 3 enhances the HER/HOR performance. The role of hydroxyl-metal-water species on alkaline HOR was also discussed. [Display omitted] • The Platinum/Rhodium Oxide-Nitrogen-Doped Carbon (Pt/Rh 2 O 3 -CN x) nanocomposite was prepared for bifunctional HER/HOR in base media. • The HOR/HER activities of Pt/Rh 2 O 3 -CN x are ∼ 3.5/6 times higher than commercial Pt/C. • Experimental, theoretical studies suggest H-spillover increases catalytic activity. • HBE and OHBE are responsible for alkaline HER/HOR; a bifunctional mechanism was proposed. • Interfaces, porosity, ECSA, and synergetic interactions also helped for high activity. The poor activity of Pt-based-catalysts for alkaline hydrogen oxidation/evolution reaction (HOR/HER) encourages scientific society to design an effective electrocatalyst to develop alkaline fuel cells/electrolyzers. Herein, platinum/rhodium oxide-nitrogen-doped carbon (Pt/Rh 2 O 3 -CN x) composite is prepared for alkaline HER and HOR inspired by hydrogen spillover. The HER performance of Pt/Rh 2 O 3 -CN x is ∼ 6 times higher than Pt/C. In HOR, Pt/Rh 2 O 3 -CN x possesses an exchange current density of 657.60 mA/mg metal , which is ∼ 3.4 times higher than Pt/C. Hydrogen and hydroxyl binding energy (HBE and OHBE) contribute equally to alkaline HOR/HER. The experimental and theoretical evidence suggests that the enhanced HER and HOR activity of Pt/Rh 2 O 3 -CN x may be due to hydrogen spillover from Pt to Rh 2 O 3. Small work function difference [0.08 eV] of the system suggested hydrogen-spillover is feasible, which has been justified by reaction-free energy calculations. We proposed that the dissociation of hydrogen (H 2) and water (H 2 O) occurs at Pt to form Pt-adsorbed hydrogen species (Pt-H ad). Then, some H ad moves to Rh 2 O 3 through hydrogen spillover and reacts with neighboring H ad or adsorbed hydroxyl species (OH ad) to form H 2 or H 2 O, which enhances the HER and HOR activity, respectively. The role of water-metal-hydroxyl species in the electrical double layer was also demonstrated on alkaline HOR/HER. This work may help to design the hydrogen-spillover-based catalysts for several renewable energy technologies. [ABSTRACT FROM AUTHOR]

We stand fully behind our earlier suggestion [Raymond & Girolami (2023). Acta Cryst. C79, 445–455] that the claim by Fish and co‐workers [Chen et al. (1995). J. Am. Chem. Soc.117, 9097–9098; Smith et al. (2014). Organometallics, 33, 2389–2404] of a linear two‐coordinate rhodium(I) species is incorrect, and that the putative rhodium atom is in fact silver. [ABSTRACT FROM AUTHOR]

A carbon‐rich molecule is synthesized, which mainly contains conjugated sp2 and sp hybridized carbon centers. Alkenyl and alkynyl binding sites are arranged such that this compound serves as ligand to a binuclear metal unit with a RhI─RhI bond. Furthermore, CH units are placed in proximity to the metal centers. The dicationic complex [Rh2(bipy)2{Ph2Ptrop(C≡CCy)2}]2+(OTf−)2 allows to study possible responses of the carbon‐framework to redox reactions as well as deprotonation reactions. All products are, whenever possible, characterized by X‐ray diffraction (XRD) methods, NMR and EPR spectroscopy as well as electrochemical methods. It is shown that the carbon skeleton of the ligand framework undergoes C─C bond rearrangement reactions of remarkable diversity. In combination with DFT (density functional theory) studies, these results allow to gain insight into the electronic structure changes caused by metal sites in a carbon‐rich environment, which may be of relevance for the properties of metal particles on carbon support materials when they are exposed to hydrogen, electrons, or protons. [ABSTRACT FROM AUTHOR]

Previously, we demonstrated the synthesis of a well-defined hydroxyalkyl-functionalized N-heterocyclic carbene (NHC)/Ru(II) complex through the transmetalation reaction between [RuCl2(p-cymene)]2 and the corresponding NHC/Ag(I) complex derived from a chiral benzimidazolium salt using the Ag2O method. In this study, we successfully synthesized [RhX(cod)(NHC)] complexes through a one-pot deprotonation route. The hydroxyalkyl-substituted benzimidazolium salt reacted with [Rh(OH)(cod)]2 in THF at room temperature, affording the corresponding monodentate NHC/Rh(I) complex in nearly quantitative yield. The rhodium complex was characterized using NMR, HRMS measurement, and elemental analysis. [ABSTRACT FROM AUTHOR]

Commercially available and air- and moisture-stable rhodium complex [Rh(OH)(cod)]2 (2) was utilized in the synthesis of [RhX(cod)(NHC)] (3). The presence of an OH group in complex 2 serves as an internal base, facilitating the deprotonation of the C–H bond of the azolium ring in the hydroxyamide-substituted benzimidazolium salt 1. This reaction between 1 and 2 proceeded in THF at room temperature without temperature control, affording the desired NHC/Rh complex 3 in excellent yield. The characterization of complex 3 was accomplished through NMR and HRMS analyses, revealing its existence as a diastereomeric mixture of two NHC/Rh complexes. Furthermore, its catalytic performance was briefly evaluated in the reaction between 2-naphthaldehyde (5) and phenylboronic acid (6). [ABSTRACT FROM AUTHOR]

Abstract In the context of the growing importance of heterocyclic compounds across various disciplines, numerous strategies for their construction have emerged. Exploiting the distinctive properties of cyclopropenes, this study introduces an innovative approach for the synthesis of benzo‐fused five‐membered oxa‐ and aza‐heterocycles through a formal [4+1] cyclization and subsequent acid‐catalyzed intramolecular O‐ to N‐ rearrangement. These transformations exhibit mild reaction conditions and a wide substrate scope. The applications in the late‐stage modification of complex molecules and in the synthesis of a potential PD‐L1 gene down‐regulator, make this method highly appealing in related fields. Combined experimental mechanistic studies and DFT calculations demonstrate Rh(III)‐mediated sequential C─H coupling/π‐allylation/dynamically favorable O‐attack route.

Abstract In the growing field of peptidomimetics, there is a constant need for new synthetic methods to generate new bioactive compounds. Herein, we present an atom‐economic approach for the branched‐selective allylation of aliphatic amine moieties of α‐amino acids and small oligopeptides. This Rh‐catalyzed hydroamination of allenes with a commercially available ligand forms a new stereocenter, often chemoselectively, in a catalyst‐controlled manner, providing high yields and stereoselectivities without the need for an additive. The method is shown to be effective in gram scale without the need for column chromatography for purification, and ready‐to‐use allylated substrates for solid‐phase peptide synthesis can be synthesized in two steps from the products of the catalysis.

Introduction. The development of methodological issues of optimizing the activities of mining and metallurgical companies and the sale of platinum group metals are highly relevant in the current market conditions due to sanctions restrictions and the severance of international economic ties. Theoretical analysis. The concept of an optimization model is formulated, the main goals for the sales unit of a mining and metallurgical company are determined, a balanced approach to monthly planning is justified, which involves dividing the sales volume into two parts: under long-term contracts and on the spot market, and the stages of constructing an optimization sales model are developed. Empirical analysis. An optimization model is presented for calculating sales volumes of platinum, palladium and rhodium within two months to obtain maximum operating profit. The model is based on regression modeling of prices for platinum group metals, a cost model built on open data from a Russian mining and metallurgical company. Results. Approbation of the methodology made it possible to justify the sales volumes of platinum group metals in two forecast periods depending on the price environment, which provide the opportunity to increase the total profit of the company under given restrictions.

In this computational study, the preferential adsorption and co-adsorption sites of various chemical species (N, O, and NO) on the Pt (111) and Rh3Pt (111) surfaces were identified. The preferential adsorption site for NO and co-adsorption sites for N and O on the Pt (111) surface are the hollow (fcc) sites; and these on the Rh3Pt (111) surface are the hollow (fcc1) site and hollow N(hcp2)-O(fcc1) sites, respectively. The activation energies of the NO dissociation reaction on the Pt (111) and Rh3Pt (111) catalytic surfaces are 2.35 and 2.02 eV, respectively. The lower activation energy of the NO decomposition on the Rh3Pt (111) surface is explained by the stronger back-donation from the 4d orbital of the Rh atoms to the 2π* anti-bonding orbital of the NO molecule. The activation energies of the N and O recombination reaction on the Pt (111) and Rh3Pt (111) catalytic surfaces are 1.51 and 2.30 eV, respectively. The study indicates that the Rh3Pt (111) surface not only facilitates the NO decomposition but also better prevents N and O from recombination. Copyright © 2024 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Introduction. The first part of the paper reveals the concept and features of platinum group metals. According to the complex of considered parameters of each platinum group metals, including the market volume in physical and value terms, we distinguish three major (palladium, platinum, rhodium) and two minor (iridium, ruthenium) metals. For this research, the markets of five platinum group metals are identified as the object for factor analysis. Theoretical analysis. The platinum group metals market is systematized into two groups: supply factors and demand factors. It also analyzes primary and secondary sources of metals, and provides an overview of key application industries for each metal. Empirical analysis. Based on historical data, we compiled correlation matrices of fundamental factors interrelation between each other and with metal prices. Taking into account the identified correlation dependencies, regression models were developed, which, with a certain degree of accuracy, enable to forecast price dynamics. Results. Carrying out a factor analysis, in addition to stated dependencies and fundamental indicators quantitative assessments, we have summarized platinum group metals market trends.

[Display omitted] Acute kidney injury (AKI) results from the rapid deterioration of renal function, which is mainly treated by transplantation and dialysis, and has a high mortality rate. Inflammation induced by excess reactive oxygen/nitrogen species (RONS) plays a crucial role in AKI. Although small molecule antioxidants have been utilized to alleviate AKI, low bioavailability and side-effect of these drugs tremendously limit their clinical use. Hence, we successfully construct ultra-small (2–4 nm) rhodium nanoparticles modified with l -serine (denoted as Rh-Ser). Our results show that Rh-Ser with multiple enzyme-mimicking activities, allows remove various RONS to protect damaged kidney cells. Additionally, the ultrasmall size of Rh-Ser is conducive to enrichment in the renal tubules, and the modification of l -serine enables Rh-Ser to bind to kidney injury molecule-1, which is highly expressed on the surface of damaged renal cells, thereby targeting the damaged kidney and increasing the retention time. Moreover, Rh-Ser allows the production of oxygen at the inflammatory site, thus further improving hypoxia and inhibiting pro-inflammatory macrophages to relieve inflammation, and increasing the survival rate of AKI mice from 0 to 80%, which exhibits a better therapeutic effect than that of small molecule drug. Photoacoustic and fluorescence imaging can effectively monitor and evaluate the enrichment and therapeutic effect of Rh-Ser. Our study provides a promising strategy for the targeted treatment of AKI via RONS scavenging and inflammatory regulation. [ABSTRACT FROM AUTHOR]

Hydroformylation of olefins is widely used in the chemical industry due to its versatility and the ability to produce valuable aldehydes with 100% atom economy. Herein, a hybrid phosphate promoter was found to efficiently promote rhodium-catalyzed hydroformylation of styrenes under remarkably mild conditions with high regioselectivities. Preliminary mechanistic studies revealed that the weak coordination between the Rhodium and the P=O double bond of this pentavalent phosphate likely induced exceptional reactivity and high ratios of branched aldehydes to linear products. [ABSTRACT FROM AUTHOR]

This study examines the kinetics and mechanism of the oxygen reduction reaction (ORR) on a polycrystalline rhodium electrode (Rh(poly)) in acidic and alkaline media, using rotating disc electrode measurements. This study found that the ORR activity of the Rh(poly) electrode decreases in the order of 0.1 M NaOH > 0.1 M HClO4 > 0.05 M H2SO4 concerning the half-wave potentials. The Tafel slopes for ORR on Rh(poly) in the cathodic direction are 60 and 120 mV dec−1 at low and high overpotentials, respectively, in perchloric acid and alkaline solutions. However, strongly adsorbed sulfate anions hinder the ORR on Rh(poly) in sulfuric acid, leading to higher Tafel slopes. The highest ORR activity of Rh(poly) in an alkaline media suggests the promoting role of the specifically adsorbed OH− anions and RhOH. In all cases, ORR on Rh(poly) proceeds through the 4e-series reaction pathway. [ABSTRACT FROM AUTHOR]

The high-pressure and high-temperature thermodynamic properties of rhodium (up to 2000 K and 300 GPa) are presented using the first principle approach within the quasi-harmonic approximation. The thermal Helmholtz free energy includes the contribution of both phonon vibrations and electronic excitations. The performance of three popular exchange-correlation functionals—local density approximation [Perdew et al., Phys. Rev. B 23, 5048 (1981)], Perdew–Burke–Ernzerhof generalized gradient approximation (PBE) [Perdew et al., Phys. Rev. Lett. 77, 3865 (1996)], PBE modified for dense solids [Perdew et al., Phys. Rev. Lett. 100, 136406 (2008)] are shown. The simulated thermal expansion coefficient, isobaric heat capacity, mode-Grüneisen parameter, thermodynamic average Grüneisen parameter, and bulk modulus are compared with the available experimental and theoretical reports. The contribution of thermal electronic excitations to the obtained thermodynamic parameters is significant at low pressure and high temperatures, except in bulk modulus, where it is small. The pressure-dependent elastic constant coefficient (Cij) and the Debye temperature are computed at 0 K. The Pugh ratio calculated from Cij indicates that rhodium undergoes brittle to ductile transitions at an average pressure of 7.45 GPa. [ABSTRACT FROM AUTHOR]

The design and commissioning of a cell suitable for operando studies using high‐energy‐resolution fluorescence‐detected X‐ray absorption near‐edge structure (HERFD‐XANES) spectroscopy in the tender X‐ray regime is reported. The cell is optimized for measurements within the energy range of 1.5 keV to 4.5 keV. It has a plug‐flow geometry and can be used for sieved powder samples, analogous to reactors employed for laboratory tests. The functionality of the spectroscopic cell is demonstrated in the area of emission control using CO oxidation as target reaction over 1 wt.% Rh/γ‐Al2O3 as catalyst. We show how HERFD‐XANES at the Rh L3‐edge captures variations in the noble metal structure resulting from the interaction with the support material and reactant molecules. Moreover, distinct structural changes were identified along the catalyst bed as a function of temperature and local gas mixture. [ABSTRACT FROM AUTHOR]

The controlled formation of mixed-metal bimetallics was realised through use of a fac-[Re(CO)3(N,N′-bpy-P)Cl] complex bearing an exogenous 2,4,6-trioxa-1,3,5,7-tetramethyl-8-phosphaadamantane donor at the 5-position of the bpy. The introduction of gold, silver, and rhodium with appropriate secondary ligands was readily achieved from established starting materials. Restricted rotation about the C(bpy)-P bond was observed in several of the bimetallic complexes and correlated with the relative steric bulk of the second metal moiety. Related chemistry with the 6-substituted derivative proved more limited in scope with only the bimetallic Re/Au complex being isolated. [ABSTRACT FROM AUTHOR]

A enantioselective tandem transformation, concerning asymmetric allylic decarboxylative addition and cyclization of N-nosylimines with vinylethylene carbonates (VECs), in the presence of [Rh(C2H4)2Cl]2, chiral sulfoxide-N-olefin tridentate ligand has been developed. The reaction of VECs with various substituted N-nosylimines proceeded smoothly under mild conditions, providing highly functionalized oxazolidine frameworks in good to high yields with good to excellent enantioselectivity. [ABSTRACT FROM AUTHOR]

The title complex [{PhS(tBuN)2}(Cl)Ge:→RhCl(cod)] (2) was synthesized by the reaction of three-coordinated chlorogermylene, [PhS(tBuN)2]GeCl (1), supported by a diimidosulfinate ligand with a half equivalent of [RhCl(cod)]2 in benzene. The molecular structure of 2 was determined by 1H and 13C NMR spectroscopies and single-crystal X-ray diffraction (SCXRD) analysis. The electronic property of germylene 1 was assessed by determining the Tolman electronic parameter of the corresponding cis-dicarbonyl Rh(I) complex, [{PhS(tBuN)2}(Cl)Ge:→RhCl(CO)2] (3), that was prepared by the treatment of 2 with carbon monoxide. [ABSTRACT FROM AUTHOR]

The heterogenization of molecular catalysts within a porous solid acting as macroligand can advantageously open access to enhanced stability and productivity, and thus to more sustainable catalytic process. Herein, a porous organic polymer (POP) made through metal‐free polymerization using bipyridine repeating units is reported. This N‐rich POP is an efficient macroligand for the heterogenization of molecular rhodium complexes. The intrinsic catalytic activity of the heterogenized catalyst is slightly higher than that of its homogeneous molecular counterpart for formic acid production as a unique carbon‐containing product. The heterogenization of the rhodium catalysts enables recycling for a total productivity of up to 8.3 g of formic acid per gram of catalyst after 7 reuses using visible light as the sole energy source. [ABSTRACT FROM AUTHOR]

A new, cationic N-heterocyclic carbene RhI complex with a tetrafluoridoborate counter-anion, [Rh(C8H12)(C8H15N3)(C18H15P)]BF4, has been synthesized and structurally characterized. There are two independent ion pairs in the asymmetric unit. Each complex cation exhibits a distorted square-planar conformation around the RhI atom. Bond lengths and bond angles are as expected for an Rh–NHC complex. There are several close, non-standard C—H...F hydrogen-bonding interactions between the ions. One of the tetrafluoridoborate anions shows statistical disorder of the F atoms.

A new neutral triazole-based N-heterocyclic carbene rhodium(I) complex [RhCl(C8H12)(C8H15N3)], has been synthesized and structurally characterized. The complex crystallizes with two molecules in the asymmetric unit. The central rhodium(I) atom has a distorted square-planar coordination environment, formed by a cycloocta-1,5-diene (COD) ligand, an N-heterocyclic carbene (NHC) ligand, and a chlorido ligand. The bond lengths are unexceptional. A weak intermolecular non-standard hydrogen-bonding interaction exists between the chlorido and NHC ligands.

The regioselective functionalization of fullerenes holds significant promise for applications in the fields of medicinal chemistry, materials science, and photovoltaics. In this study, we investigate the regioselectivity of the rhodium(I)-catalyzed [2 + 2 + 2] cycloaddition reactions between diynes and C70 as a novel procedure for generating C70 bis(fulleroid) derivatives. The aim is to shed light on the regioselectivity of the process through both experimental and computational approaches. In addition, the photooxidation of one of the C–C double bonds in the synthesized bis(fulleroids) affords open-cage C70 derivatives having a 12-membered ring opening.

Phospholane-phosphites are known to show highly unusual selectivity towards branched aldehydes in the hydroformylation of terminal alkenes. This paper describes the synthesis of hitherto unknown unsaturated phospholene borane precursors and their conversion to the corresponding phospholene-phosphites. The relative stereochemistry of one of these ligands and its Pd complex was assigned with the aid of X-ray crystal structure determinations. These ligands were able to approach the level of selectivity observed for phospholane-phosphites in the rhodium-catalysed hydroformylation of propene. High-pressure infra-red (HPIR) spectroscopic monitoring of the catalyst formation revealed that whilst the catalysts showed good thermal stability with respect to fragmentation, the C=C bond in the phospholene moiety was slowly hydrogenated in the presence of rhodium and syngas. The ability of this spectroscopic tool to detect even subtle changes in structure, remotely from the carbonyl ligands, underlines the usefulness of HPIR spectroscopy in hydroformylation catalyst development. [ABSTRACT FROM AUTHOR]

The hydrogenation of C=C bonds in styrene−butadiene rubber (SBR), catalyzed by RhH(P(i-Pr)3)3, was experimentally investigated. Tris(triisopropylphosphine)hydridorhodium(I), RhH(P(i-Pr)3)3 (i-Pr=CH(CH3)2) was prepared by using rhodium chloride (RhCl3), tetrahydrofuran (THF), triisopropylphosphine (P(i-Pr)3) and a sodium mercury amalgam. The effect of catalyst/polymer ratio, reaction temperature, and hydrogen pressure on the reactivity of the catalytic system has been studied. The optimal experimental condition was obtained. The hydrogenated styrene-butadiene rubber (HSBR) was analyzed by FT-IR and 1H-NMR. In the absence of any additives, the conversion of C=C bonds in SBR could easily reach 95% in a short period of time, and no obvious cross-linking was observed. The dynamic properties of SBR did not change after the hydrogenation of the unsaturated C=C bonds. A preliminary reaction mechanism was also proposed. This study provides a new route, not only for the chemical modification of SBR by using a rhodium complex but also for the hydrogenation of other unsaturated polymers, such as diene-based rubbers. [ABSTRACT FROM AUTHOR]

The catalytic activity of rhodium-containing nanocomposites with carbon nanodots and Si, Al and Zr oxides in high-temperature water shift reaction has been established. The role of support lies in regulation of the surface concentration of the active component (Rh) and its localization. The use of the support with a low specific surface promote the localization of the active component on the external surface that leads to the decrease of the distance between supported Rh particles, which is important for the surface migration of intermediate products of the reaction. [ABSTRACT FROM AUTHOR]

Noble metals are key to various research fields and noble metal nanomaterials are directly relevant to optics, catalysis, medicine, sensing and many other applications. Rhodium-based nanomaterials have been less studied than metals such as gold, silver or platinum. There have been many improvements in characterisation tools over the years and knowledge about rhodium chemistry and nanomaterials is growing rapidly. Rhodium nanoparticles are widely used as catalysts for automotive emissions control and for hydrogen and oxygen precipitation reactions in electrolytic cells. Novel applications in electronics, anticancer drugs and aerospace are being revisited. In Part I of this two-part review, we cover different strategies for the synthesis of rhodium films and nanoparticles. [ABSTRACT FROM AUTHOR]

Part I of this review covered the synthesis methods for synthesis of rhodium films and nanoparticles (1). In Part II, we review the literature on the current and potential applications of rhodium and rhodium alloy films and nanoparticles in catalysis, components for the glass, chemical and electronic industries, thermal sensors and anticancer drugs. [ABSTRACT FROM AUTHOR]

An efficient method of accessing new CF3-containing spiro-[indene-proline] derivatives has been developed based on a Cp*Rh(III)-catalyzed tandem C-H activation/[3+2]–annulation reaction of 5-aryl-2-(trifluoromethyl)-3,4-dihydro-2H-pyrrole-2-carboxylates with alkynes. An important feature of this spiro annulation process is the feasibility of dehydroproline moiety to act as a directing group in the selective activation of the aromatic C-H bond. [ABSTRACT FROM AUTHOR]

Commercially available and air- and moisture-stable rhodium complex [Rh(OH)(cod)]2 (2) was utilized in the synthesis of [RhX(cod)(NHC)] (3). The presence of an OH group in complex 2 serves as an internal base, facilitating the deprotonation of the C–H bond of the azolium ring in the hydroxyamide-substituted benzimidazolium salt 1. This reaction between 1 and 2 proceeded in THF at room temperature without temperature control, affording the desired NHC/Rh complex 3 in excellent yield. The characterization of complex 3 was accomplished through NMR and HRMS analyses, revealing its existence as a diastereomeric mixture of two NHC/Rh complexes. Furthermore, its catalytic performance was briefly evaluated in the reaction between 2-naphthaldehyde (5) and phenylboronic acid (6).

Previously, we demonstrated the synthesis of a well-defined hydroxyalkyl-functionalized N-heterocyclic carbene (NHC)/Ru(II) complex through the transmetalation reaction between [RuCl2(p-cymene)]2 and the corresponding NHC/Ag(I) complex derived from a chiral benzimidazolium salt using the Ag2O method. In this study, we successfully synthesized [RhX(cod)(NHC)] complexes through a one-pot deprotonation route. The hydroxyalkyl-substituted benzimidazolium salt reacted with [Rh(OH)(cod)]2 in THF at room temperature, affording the corresponding monodentate NHC/Rh(I) complex in nearly quantitative yield. The rhodium complex was characterized using NMR, HRMS measurement, and elemental analysis.

Abstract Rh‐promoted YZr‐supported Ni catalyst (5Ni/YZr) is investigated for DRM and characterized with X‐ray diffraction, Raman, infrared spectroscopy, cyclic reduction–oxidation–reduction temperature programmed experiment, thermogravimetry, and transmission electron microscope. Over 5Ni/YZr, some active sites become inactive under the CO2 stream and limit H2 yield to ∼71%. Upon 4 wt% Rh addition over 5Ni/YZr; more than one type of stable active sites (Rh and Ni) generates, moderate basic sites are enhanced, wide ranges of CO2‐interacted surface species (especially bidentate CO2‐adsorbed species) are grown and graphitic carbon proportion over spent catalyst declines. This resulted in 87.35% H2 yield and 86.73% CO yield up to 420 min. 5Ni4Rh/YZr catalyst maintains ∼80% H2 yield at the end of 27 h of DRM reaction.

Rhodium is one of the scarcest, most valuable, and useful platinum group metals, a strategically important material relied on heavily by automotive and electronics industries. The limited finite natural sources of Rh and exponentially increasing demands on these supplies mean that new sources are being sought to stabilise supplies and prices. Spent nuclear fuel (SNF) contains a significant quantity of Rh, though methods to recover this are purely conceptual at this point, due to the differing chemistry between SNF reprocessing and the methods used to recycle natural Rh. During SNF reprocessing, Rh partitions between aqueous nitric acid streams, where its speciation is complex, and insoluble fission product waste streams. Various techniques have been investigated for Rh recovery during SNF reprocessing for over 50 years, including solvent extraction, ion exchange, precipitation, and electrochemical methods, with tuneable approaches such as impregnated composites and ionic liquids receiving the most attention recently, assisted by more the comprehensive understanding of Rh speciation in nitric acid developed recently. The quantitative recovery of Rh within the SNF reprocessing ecosystem has remained elusive thus far, and as such, this review discusses the recent developments within the field, and strategies that could be applied to maximise the recovery of Rh from SNF.

The title complex [{PhS(tBuN)2}(Cl)Ge:→RhCl(cod)] (2) was synthesized by the reaction of three-coordinated chlorogermylene, [PhS(tBuN)2]GeCl (1), supported by a diimidosulfinate ligand with a half equivalent of [RhCl(cod)]2 in benzene. The molecular structure of 2 was determined by 1H and 13C NMR spectroscopies and single-crystal X-ray diffraction (SCXRD) analysis. The electronic property of germylene 1 was assessed by determining the Tolman electronic parameter of the corresponding cis-dicarbonyl Rh(I) complex, [{PhS(tBuN)2}(Cl)Ge:→RhCl(CO)2] (3), that was prepared by the treatment of 2 with carbon monoxide.

The aim of this study was to prepare poly-N-isopropylmethacrylamide-co-acrylic acid-acrylamide [p-(NIPMAM-co-AA-AAm)] via precipitation polymerization in an aqueous medium. Rhodium nanoparticles were formed in the microgel network by an in-situ reduction technique with the addition of sodium borohydride as a reducing agent. Pure p-(NIPMAM-co-AA-AAm) and hybrid microgels [Rh-(p-NIPMAM-co-AA-AAm)] microgels were examined by using UV–Visible, FTIR (Fourier Transform Infrared), SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), DLS (Dynamic Light Scattering) and XRD (X-Ray Diffraction) techniques. The catalytic activities of the hybrid microgel [Rh-(p-NIPMAM-co-AA-AAm)] for the degradation of azo dyes such as alizarin yellow (AY), congo red (CR), and methyl orange (MO) were compared and the mechanism of the catalytic action by this system was examined. Various parameters including the catalyst amount and dye concentration influenced the catalytic decomposition of azo dyes. In order to maximize the reaction conditions for the dye's quick and efficient decomposition, the reaction process was monitored by spectroscopic analysis. The rate constants for reductive degradation of azo dyes were measured under various conditions. When kapp values were compared for dyes, it was found that [Rh-(p-NIPMAM-co-AA-AAm)] hybrid microgels showed superior activity for the degradation of MO dyes compared to the reductive degradation of CR and AY.

In the title triazole-based N-heterocyclic carbene rhodium(I) cationic complex with a tetrafluoridoborate counter-anion, [Rh(C8H12)(C8H15N3)(C18H15P)]BF4, which crystallizes with two cations and two anions in the asymmetric unit, the Rh center has a distorted square-planar coordination geometry with expected bond distances. Several nonclassical C—H...F hydrogen-bonding interactions help to consolidate the packing. Two of the F atoms of one of the anions are disordered over adjacent sites in a 0.814 (4):0.186 (4) ratio.

For the industrially relevant hydroformylation of but‑1-ene the concept of supported ionic liquid phase (SILP) has been applied previously. In this work, we have studied the influence of the type of ionic liquid (imidazolium and phosphonium based cations, various anions) on the solubility of the three reagents but‑1-ene, carbon monoxide and hydrogen. For the olefin, the predicted solubility values were determined using the COSMO-RS software tool. These data were compared to the experimentally determined values. A correlation between the predicted solubility and the observed activity within similar ILs could be observed. The highest activity could be obtained with the IL [N1888][NTf2]. A variation of the olefin chain length supported the observed correlation between solubility and activity. With increasing chain length, the activity of the SILP catalyst also increased. For the undesired consecutive reaction leading to aldols it was found that the substrate solubility does not significantly influence the activity or hydrocarbon accumulation under the used reaction conditions. The anion had a more pronounced effect on the accumulation of aldols, with hydrophilic Cl− and [EtOSO3]− showing lowest accumulation as well as aldol formation activity, while [NTf2]− showed highest values for both accumulation and formation activity. It was shown that the Kamlet-Taft-parameter β is a suitable value to be correlated with activity and accumulation for different ILs.

The nanointerface CeO 2 /Rh anchored on CNT is constructaed, wherein adjustable charge transfer between CeO 2 and Rh could simultaneously resultac in optimized oxygen vacancy concentration of CeO 2 and positive charges of Rh, leading to CeO 2 /Rh possessing of superior hydrogen oxidation reaction performance in alkaline electrolyte than that of state-of-the-art Pt. [Display omitted] Sluggish kinetics of hydrogen oxidation reaction (HOR) in alkaline solution has restricted the rapid development of hydrogen economy. Constructing catalyst with metal-oxide heterostructures can enhance HOR performance; however, little studies concentrate on charge transfer between them, and the corresponding effects on reactions remain unclear. Herein, we report charge-transfer-adjustable CeO 2 /Rh interfaces uniformly dispersed on multiwalled carbon nanotube (CNT), which exhibit excellent alkaline HOR performance. Results confirm that the charge transfer from Rh to CeO 2 could be conveniently tuned via thermal treatment. Consequently, the adsorption free energies of H* in Rh sites and OH* adsorption strength in CeO 2 could be adjusted, as corroborated by density functional theory study. The optimized CeO 2 /Rh interfaces exhibit an exchange current density and a mass-specific kinetic current of 0.53 mA cm PGM −2 and 830 A g PGM −1 at an overpotential of 50 mV, respectively, which surpasses most of the advanced noble-metal-based electrocatalysts. This work provides a new insight of harnessing charge transfer of heterostructure to enhance catalytic activities. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rh nanoparticles anchored on Co/ N -doped carbon nanofibers are prepared via an electrospinning-pyrolysis-reduction method. • The nanofibrous hybrid catalyst shows rich exposed active sites and excellent electrical conductivity. • The nanofibrous hybrid catalyst presents high HER activities in both alkaline and acidic media. • The nanofibrous hybrid catalyst presents an excellent long-term stability towards HER. Constructing high-activity electrocatalysts towards hydrogen evolution reaction (HER) is an essential way to achieve efficient, green and sustainable energy from water electrolysis. In this work, rhodium (Rh) nanoparticles anchored on cobalt (Co)/nitrogen (N)-doped carbon nanofibers (NCNFs) catalyst is prepared by the electrospinning-pyrolysis-reduction method. The synergy effect between Co-NCNFs and Rh nanoparticles contributes to the superior HER activity and favorable durability. The optimized 0.15Co-NCNFs-5Rh sample exhibits ultralow overpotentials of 13 and 18 mV to reach 10 mA cm−2 in an alkaline and acidic electrolyte, surpassing many Rh-based or Co-based electrocatalysts reported in the literature. Additionally, the Co-NCNFs-Rh sample shows a better HER activity than benchmark Pt/C catalyst in an alkaline medium at all current densities and in an acidic condition at higher current densities, offering its promising practical applications. Thus, this work provides an efficient methodology to construct high-performance HER electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] Immune checkpoint blockade has emerged as a significant therapeutic development in immunotherapy during the past decade. However, only a small percentage of cancer patients respond to checkpoint blockade, suggesting that a fundamental knowledge of the underlying processes of immune checkpoint receptor signaling remains elusive and that novel therapeutic medications are needed. Here, the programmed cell death protein 1(PD-1) expressing nanovesicles were developed to enhance T cell activity. Iguratimod (IGU) and Rhodium (Rh) nanoparticles (NPs) were loaded in PD-1 nanovesicles (NVs) for synergistic therapeutic antitumor effects against lung cancer and metastasis. For the first time, this study revealed that IGU exhibits an antitumor effect by inhibiting the phosphorylation of mammalian target of rapamycin (mTOR) and Rh-NPs provided a photothermal effect by improving reactive oxygen species (ROS)-dependent apoptosis in lung cancer cells. IGU-Rh-PD-1 NVs also reduced the migration ability through the epithelial-mesenchymal transition (EMT) pathway. Furthermore, IGU-Rh-PD-1 NVs reached the targeted site and inhibited tumor growth in vivo. This strategy could boost T cell performance and simultaneously possess chemotherapeutic and photothermal therapy to serve as a new combination therapy for lung cancer and potentially other aggressive cancer. [ABSTRACT FROM AUTHOR]

Transition-metal-catalyzed cross-coupling reactions as very efficient and atom-economical approaches have been widely used to build up complex heterocyclic compounds. However, modification of 2-oxyl benzimidazole skeleton using maleimide compounds via C-H activation has remained unprecedented. Herein, we developed a rhodium(III)-catalyzed [5 + 1] cascade spiroannulation to construct diversified novel benzimidazole-incorporated spirosuccinimide derivatives from 2-oxyl benzimidazoles and maleimides. [ABSTRACT FROM AUTHOR]

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Accurate computations of experimental observables are essential for interpreting the high information content held within x-ray spectra. However, for complicated systems this can be difficult, a challenge compounded when dynamics becomes important owing to the large number of calculations required to capture the time-evolving observable. While machine learning architectures have been shown to represent a promising approach for rapidly predicting spectral lineshapes, achieving simultaneously accurate and sufficiently comprehensive training data is challenging. Herein, we introduce Δ-learning for x-ray spectroscopy. Instead of directly learning the structure-spectrum relationship, the Δ-model learns the structure dependent difference between a higher and lower level of theory. Consequently, once developed these models can be used to translate spectral shapes obtained from lower levels of theory to mimic those corresponding to higher levels of theory. Ultimately, this achieves accurate simulations with a much reduced computational burden as only the lower level of theory is computed, while the model can instantaneously transform this to a spectrum equivalent to a higher level of theory. Our present model, demonstrated herein, learns the difference between TDDFT(BLYP) and TDDFT(B3LYP) spectra. Its effectiveness is illustrated using simulations of Rh L3-edge spectra tracking the C–H activation of octane by a cyclopentadienyl rhodium carbonyl complex. [ABSTRACT FROM AUTHOR]

Organic amines are important compounds present in a wide variety of products, which makes the development of new systems for their detection an interesting field of study. New organometallic complexes of group 9 [MCp*X(2′-R-2-py-SBF)] (M = Ir, Rh; R = H, X = Cl (6), R = H, X = OAc (7), R = CHO, X = Cl (8)), and [IrCp*Cl(2′, 7-diCHO-2-py-SBF)] (9) (Cp* pentamethylcyclopentadienyl, SBF = 9,9'-spirobifluorene) bearing bidentate C–N ligands based on 9,9′-spirobifluorene were obtained and characterized by NMR spectroscopy, mass spectrometry, IR spectroscopy, and X-ray diffraction analysis when possible. The formation of a Schiff base to give complexes with the formula [MCp*Cl(2′-CH=NR-2-py-SBF)] (M = Ir, Rh; R = alkyl or aryl (10–12)), through condensation of an amine, and the aldehyde group present in these new complexes was studied leading to a selective reactivity depending on the nature of the amine and the metal center. While the iridium complexes only react with aromatic amines, the rhodium derivative requires heat for those but can react at room temperature with aliphatic amines. [ABSTRACT FROM AUTHOR]

Triphenylphosphine acetylacetone carbonyl rhodium (ROPAC) is an important catalyst in the petrochemical industry, and its deactivated waste catalyst holds significant value for recovery. This study focuses on the existing forms of rhodium (Rh) in waste catalysts and the current status of traditional processes. A green, efficient, and continuous recovery technique was developed using a sealed stainless steel microchannel reactor. The influence of reaction temperature, reaction time, and phase ratio on the Rh recovery rate was investigated, and the process parameters were optimized using response surface methodology (RSM). The results indicate that the magnitude of the impact on the Rh recovery rate follows the order: reaction temperature > reaction time > phase ratio. The optimized process parameters were determined as follows: a reaction time of 29 min, a reaction temperature of 110 °C, and a phase ratio of 1:1, with a corresponding maximum recovery rate of Rh of 66.06%. Furthermore, secondary treatment was performed on the organic phase after primary recovery using the same process conditions, resulting in an overall Rh recovery rate of 95.6%, indicating satisfactory recovery efficiency. Moreover, the application of FTIR and ICP-OES analysis provided definitive evidence that the oxidative dissociation of the rhodium-phosphine chemical bond by H2O2 within ROPAC leads to the conversion of Rh+ into Rh3+. Subsequently, Rh forms chloroaquorhodium (III) complexes that enter the aqueous phase, enabling effective recovery of Rh. [ABSTRACT FROM AUTHOR]

Simple Summary: Air pollution in urban areas represents a major environmental risk to human and ecosystem health. Our aim was to test the adequacy of the Ligustrum lucidum physiological variables as proxies for heavy metal and platinum group element pollution. Chlorophyll, nitrogen and Fv/Fm generally showed high values typical of healthy plants, and they did not seem to be consistently affected by the different pollutants. Regarding flavonoid content, it was negatively correlated with heavy metals, which did not confirm its role as a protectant against metal stress. The relatively low levels of pollution usually found in the city of Logroño, together with the influence of other environmental factors and the relative tolerance of Ligustrum lucidum to modest atmospheric pollution, probably determined the only slight response of physiological variables to heavy metals and platinum group elements. Physiological variables (the content of chlorophyll, flavonoids and nitrogen, together with Fv/Fm) and the content of ten heavy metals (As, Cd, Cu, Hg, Mn, Ni, Pb, Sb, V and Zn) and two platinum group elements (PGEs: Pd and Rh) were measured in the leaves of 50 individuals of Ligustrum lucidum trees regularly distributed in the city of Logroño (Northern Spain). Three of these variables increased with increasing physiological vitality (chlorophyll, nitrogen and Fv/Fm), whereas flavonoids increased in response to different abiotic stresses, including pollution. Our aim was to test their adequacy as proxies for the pollution due to heavy metals and PGEs. The three vitality indicators generally showed high values typical of healthy plants, and they did not seem to be consistently affected by the different pollutants. In fact, the three vitality variables were positively correlated with the first factor of a PCA that was dominated by heavy metals (mainly Pb, but also Sb, V and Ni). In addition, Fv/Fm was negatively correlated with the second factor of the PCA, which was dominated by PGEs, but the trees showing Fv/Fm values below the damage threshold did not coincide with those showing high PGE content. Regarding flavonoid content, it was negatively correlated with PCA factors dominated by heavy metals, which did not confirm its role as a protectant against metal stress. The relatively low levels of pollution usually found in the city of Logroño, together with the influence of other environmental factors and the relative tolerance of Ligustrum lucidum to modest atmospheric pollution, probably determined the only slight response of the physiological variables to heavy metals and PGEs. [ABSTRACT FROM AUTHOR]

The syntheses of new neutral square-planar pyridine di-imine rhodium and iridium complexes with O- and S-donor (OH, OR, SH, SMe and SPh) ligands along with analogous cationic compounds are reported. Their crystal and electronic structures are investigated in detail with a focus on the non-innocence/innocence of the PDI ligand. The oxidation states of the metal centers were analyzed by a variety of experimental (XPS and XAS) and theoretical (LOBA, EOS and OSLO) methods. The dπ-pπ interaction between the metal centers and the π-donor ligands was investigated by theoretical methods and revealed the partial multiple-bond character of the M-O,S bonds. Experimental support is provided by a sizable barrier for the rotation about the Ir-S bond in the methyl thiolato complex and confirmed by DFT and LNO-CCSD(T) calculations. This was corroborated by the high Ir-O and Ir-S bond dissociation enthalpies calculated at the PNO-CCSD(T) level. [ABSTRACT FROM AUTHOR]