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Two bis-(propyl-imidazolium)-napthalenediimide (NDI) salts were prepared and used as N-heterocyclic carbene (NHC) precursors for the preparation of dimetallic complexes of rhodium and iridium. Infrared spectroelectrochemical studies indicate that the metals are sensitive to changes in the electronic state of the NDI moiety. The catalytic behavior of the rhodium and iridium complexes was tested in the cycloisomerization of alkynoic acids, where the complexes showed effective redox-switching properties.

Rhodium-catalysed [3 + 3]-cycloaddition of acetanilides with CF3-ynones was achieved through a traceless directing-group strategy, which delivered 2-trifluromethylquinolines exhibiting favorable blue emissions.

Two chiral rhodium(iii) complexes with an azobenzene moiety were developed to act as photoswitchable DNA molecular locks, which can photo-regulate DNA transcription in vitro.

The increasingly stringent emission regulations make it urgent to get a fundamental understanding on the catalytic behaviors of rhodium, the most efficient component in three-way catalysts (TWCs) to convert NOx into N2. Herein, the catalytic conversion of NO and CO into N2 and CO2 by gas-phase rhodium-aluminum oxide species (RhAlO0–3 and RhAl2O1–4) was identified by mass spectrometry and quantum chemical calculations. This finding represents a significant step in the field of gas-phase catalysis, given that only elementary reactions for this conversion are commonly observed because it is extremely challenging to rupture the strong N–O bond and couple the N–N bond as well as drive the resulting product to oxidize CO. It emphasized that a polarized Rh–Al bond in gas-phase species is indispensable and the RhAlO0,1 and RhAl2O1,2 species with direct Rh–Al bonding can be involved in catalytic NO reduction by CO.

Asymmetric cyclopropanation of alkenes by aryldiazoacetates was achieved using the readily-available racemic (diene)rhodium complex in combination with the chiral oxazoline-phenol ligand, which acts as the chiral poison and selectively inhibits one of the enantiomers of the catalyst. This approach eliminates a common problematic step of the synthesis of chiral catalysts.

Broad substrate scope; high isloated yield and enantioselectivity; novel hybrid bisphosphine ligands; gram-scale reaction with lower catalyst usage.

Herein, a rhodium-catalyzed desymmetrization of dihydrosilanes with heterocyclic compounds via intermolecular dehydrogenative C–H silylation is developed.

The 0.54%(Pt, Rh, Pd or Ru)/Co(OH)2, 1.23%Rh/Co(OH)2 catalysts were successfully synthesized by simple hydrothermal and precipitation methods for nitroarenes selective hydrogenation, it was found that 0.54%Rh/Co(OH)2 outperformed other catalysts, for example, 2-chloronitrobenzene hydrogenation (turnover frequency-TOF of 575 h-1) under 3.0 MPa H2 at 100 °C for 1 h (much higher than that of 1.23%Rh/Co(OH)2-398 h-1). Through the nanostructure characterization (XRD, TEM, HRTEM, AC-STEM (spherical aberration-corrected scanning transmission electron microscope), AC-STEM-EDX elemental mapping and line-scanning, and H2-TPD, etc.), it confirmed that Rh was dispersed in the form of single atoms and ultrasmall nanoclusters on Co(OH)2 for 0.54%Rh/Co(OH)2. Moreover, 0.54%Rh/Co(OH)2 also exhibited extremely high selectivity to -NO2 hydrogenation for other selected nitroarenes substrates. It was mainly attributed to Rh as single atoms or super tiny nanoclusters in 0.54%Rh/Co(OH)2, leading to a significant increase in the number of the active sites, beneficial adsorption of -NO2-group at defect-rich Co(OH)2 and interfacial synergy effect of Rh-Co(OH)2, thus improving the catalytic performance.

Rh-catalyzed highly chemo- and enantioselective hydrogenation of chromone-2-carboxylic acids was successfully established for the first time, providing a wide range of enantiopure chromanone-2-carboxylic acids with excellent results (up to 97% yield and 99% ee) and high efficiency (up to 10 000 TON). The carboxylic group in the substrate was demonstrated to play a vital role and an enantio-induction mode was elucidated by DFT calculation. This hydrogenation protocol provided straightforward access to various bioactive chromanoids.

International audience; Electronic and steric properties of NHC ligands functionalized with porphyrins were investigated. When porphyrins are used as NHCwingtips, nickel(II) in the macrocyle significantly improves the catalytic activity of the neighbouring NHC-Rh(I) complex in the conjugate addition of phenylboronic acid to cyclohexen-2-one.

Hydrazine-directed, Rh(iii) catalyzed (4+2) annulation with sulfoxonium ylides.

Construction of a carbon-nitrogen bond is one of the most prevalent operations in nature and organic synthesis. The resulting amino compounds are privileged structural fragments in natural products, pharmaceutical drugs, and functional materials. With the rapid advancement of C-H bond activation, directing-group strategies in C-H amination catalyzed by rhodium have emerged. This reaction approach considerably enhances the step economy and atom economy of the reaction, and it complies with green chemistry and atom economy. The reactivity and selectivity of chelation-assisted rhodium-catalyzed C-H amination are discussed in relation to the types of aminating reagent, as well as the challenges and future development prospects in this field.

Rhodium catalyzed alkyne-tethered intramolecular annulation has been demonstrated for the synthesis of tetracyclic carbazole skeletons and a series of five to eight-membered pyrido[3,2,1

The synthesis and characterization of carbon black supported rhodium and iridium heterobimetallic catalysts, termed hybrid catalysts, and their application in the hydrosilylation of alkynes is described. An aryl diazonium grafting procedure was applied to simultaneously immobilize Rh and Ir pyrazole–triazole complexes with tethers of varying lengths to carbon black, yielding the hybrid catalysts. The complexes differ in metal centre oxidation state and co-ligands, which are CO or Cp*Cl for the Rh complexes and Cp*Cl for the Ir complexes. The immobilization results in simultaneous surface binding and modification of the Rh complexes bearing CO-ligands. In this process, the CO ligands are removed and the overall structure of the catalytically active complex is altered. Analysis of the hybrid catalysts by XPS and SEM/EDX shows that the catalysts bear both surface bound Rh- and Ir-complexes. The Rh content is substantially higher than the Ir content. This is due to more efficient binding of the modified Rh complexes to the carbon black, as they feature two potential binding sites. Synchrotron based X-ray absorption spectroscopy (XAS) at the Rh K- and Ir L3 edges further confirms the presence of the surface bound metal complexes. There is no indication that the presence of a secondary metal affects the electronic structure of the adjacent metal in the systems under investigation, for either the long or short tether derivatives. The performance of the different catalysts was assessed for promoting the hydrosilylation of alkynes, an important industrially relevant reaction. All catalysts are highly efficient. The modified Rh sites are α-selective in the product formation on activation of terminal alkynes, while the RhCp*Cl and IrCp*Cl sites are β(Z)-selective. When operating at mild conditions with high metal loadings, the surface bound Rh catalyst is the active species, while the Ir sites are inactive. At a lower overall surface coverage or higher temperature, the Ir sites become active, which allows engineering of the regioselectivity by adjusting surface coverages and metal loadings.

A rhodium-catalyzed electrochemical regioselective annulation of 6-phenylpurines and 6-phenyl-7-deazapurines with alkynes has been developed. Electricity is used to recycle the active rhodium-based catalyst, promote the evolution of H

Rhodium-catalyzed stereospecific cyanation of the olefinic C–H bond using environmentally benign N-cyano-N-phenyl-p-methylbenzenesulfonamide (NCTS) as a cyanating reagent for the synthesis of β,β-disubstituted acrylonitriles has been developed. The mechanism involves electrophilic cyanation of an alkenylrhodium intermediate which is generated in situ via 1,4-rhodium migration. This approach does not require directing groups, tolerates various functional groups, and provides a concise and green access to a wide range of disubstituted acrylonitriles in generally good to excellent yields under mild conditions.

Hydroxycarbonylation of alkenes using formic acid (HCOOH) is ideal for the synthesis of various carboxylic acids as a means to develop a sustainable reaction system with lower environmental impact. In this study, we developed a new catalytic system for hydroxycarbonylation of alkenes with HCOOH using a Vaska-type Rh complex with an iodide ligand, RhI(CO)(PPh3)2 (1), as the catalyst, and a quaternary ammonium iodide salt as the promoter for the catalyst. In comparison with similar reaction systems using Rh catalysts, our reaction system is safer and more environmentally friendly since it does not require high-pressure conditions, explosive gases, or environmentally unfriendly CH3I and extra PPh3 promoters. In addition, we also experimentally clarified that the catalytic reaction proceeds via RhHI2(CO)(PPh3)2 (2), which is formed by the reaction of 1 with a quaternary ammonium iodide salt and p-TsOH. Furthermore, the Rh(III) complex 2 can catalyze hydroxycarbonylation of alkenes with HCOOH without any promoters.

A Grob-type fragmentation of an oxonium ylide generated from the intramolecular addition of oxygen to α-imino rhodium carbene was realized. The reaction was stereospecific and produced two remote double bonds. The newly formed double bonds could be employed as useful synthetic handles for further transformations. A reasonable mechanism was proposed based on primary control experiments and comparison of the stereochemistry of the starting triazoles with that of the products.

Herein, an original and divergent synthetic method for fluorinated 2-benzylated indoles and 2,2′-bis(indolyl)methanes has been established for the first time via Rh(III)-catalyzed C–H/C–F activation of arenes employing 3,3-difluoro-2-exo-methylidene indolines as novel cross-coupling partners. This redox-neutral protocol exhibited a broad substrate scope (30 examples, up to 97% yield) and high functional-group compatibility. Gram-scale and mechanistic studies were also performed.

A rhodium-catalyzed intermolecular highly stereoselective 1,3-dienylation at the 2-position of indoles with non-terminal allenyl carbonates has been developed by using 2-pyrimidinyl or pyridinyl as the directing group. The reaction tolerates many functional groups affording the products in decent yields under mild conditions. In addition to C–H bond activation, the directing group also played a vital role in the determination of Z-stereoselectivity for the C–H functionalization reaction with 4-aryl-2,3-allenyl carbonates, which is confirmed by the E-selectivity observed with 4-alkyl-2,3-allenyl carbonates. DFT calculations have been conducted to reveal that π–π stacking involving the directing 2-pyrimidinyl or pyridinyl group is the origin of the observed stereoselectivity. Various synthetic transformations have also been demonstrated., A rhodium-catalyzed intermolecular highly stereoselective 1,3-dienylation at the 2-position of indoles with non-terminal allenyl carbonates has been developed by using 2-pyrimidinyl or pyridinyl as the directing group.

An effective method for the synthesis of quinolino[2,1-b]quinazolinones has been described. The O-directing Rh(III)-catalyzed C–H activation of 3-arylquinazolinones and alkynes gave the corresponding polyaryl substituted quinolino[2,1-b]quinazolinones in good to excellent yields. The results of competition and isotope-labeling experiments support the proposed double C–H activation mechanism. The synthesized quinolino[2,1-b]quinazolinones exhibit a blue-colored emission and large Stokes shifts (67–123 nm) as well as emit visible fluorescence with good fluorescence quantum yields in the solid state.

This feature article details the progress of transition metal-catalyzed stereoselective sp2 and sp3 C-H activation and silylation in the synthesis of chiral organosilicon compounds, and the asymmetric C-H silylation includes intramolecular cyclizing silylation and intermolecular silylation. The silylating reagents include monohydrosilanes, dihydrosilanes, silacylcobutanes and disilanes. In general, catalytic systems include a transition metal salt as the catalyst and a chiral ligand. No external chiral ligand is required in some cases where the chiral substrates act as the source of chirality. Many kinds of silylated compounds with central, axial, planar, or helical chirality have been constructed via C-H activation by asymmetric rhodium, iridium or palladium catalysis. Some pharmacophores and material building blocks were successfully introduced into the target molecules. Some silylated products proved to be useful in medicinal chemistry, synthetic organic chemistry, and materials science. Besides reaction development, mechanisms for stereoselective C-H activation and silylation are also discussed.

A rhodium-catalysed direct formylmethylation adopting vinylene carbonate as an ethynol equivalent is reported. The developed catalytic system is further utilised for the oxidant-free production of esters with the liberation of hydrogen gas. Some control experiments are conducted to elucidate the reaction mechanism.

Sum frequency generation (SFG) vibrational spectroscopy is a unique surface/interface-sensitive method, enabling the identification of chemical species and molecular structures, densities and orientations. SFG has been proven to be a powerful probe to examine adsorbates and reactions at solid–gas interfaces related to heterogeneous catalysis, employing well-defined ultra-high vacuum (UHV) grown model catalysts and UHV-compatible high-pressure reaction cells, enabling bridging both the materials and pressure gaps. SFG was thus among the first methods for ambient pressure surface science, enabling the characterization of “high pressure adsorbates”. In this mini-review, we provide an overview of SFG studies of CO-related processes in heterogeneous model catalysis. This includes pressure- and/or temperature-dependent CO adsorption on single crystals (platinum, palladium, rhodium, iridium, copper, nickel) and oxide/graphene-supported (palladium, platinum) nanoparticles, as well as CO reactions (oxidation/hydrogenation) simultaneously monitored by SFG and mass spectrometry. The adsorption of isotopic CO mixtures on single crystals and nanoparticles provides information on the individual contributions of vibrational coupling and chemical interactions to the adsorbate–adsorbate interactions. Altogether, SFG helps to identify various adsorption sites, adsorbate structures, molecular orientations and CO reactions on prototypical catalyst surfaces of increasing complexity. Specifically, the analysis of molecular orientation (tilt angles) can be carried out by polarization-dependent SFG.

Developing powerful methods to introduce versatile functional groups at the N-substituents of isoquinolone scaffolds is still a great challenge. Herein, we report a novel three-component cascade annulation reaction to efficiently construct the N-oxopropyl chain of isoquinolone derivatives via rhodium(iii)-catalyzed C-H activation/cyclization/nucleophilic attack, with oxazoles used both as the directing group and potential functionalized reagents.

A series of half-sandwich polypyridyl complexes was synthesized and compared focusing on structural, cytotoxic and aqueous solution behaviour. The formula of the synthesized complexes is [M(arene)(N,N)Cl]Cl, where M: Ru or Rh, arene: p-cymene, toluene or C5Me5−, (N,N): 2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (dmb), 1,10-phenanthroline (phen) or 2,9-dimethyl-1,10-phenanthroline (neo). The structures of five half-sandwich complexes were determined by X-ray crystallography. It was found that introducing methyl groups next to the coordinating nitrogen atoms of the bidentate ligand causes steric congestion around the metal centre which changes the angle between ligand planes. The ligands and the Rh complexes showed significant cytotoxicity in A2780 and MES-SA cancer cell lines (IC50 = 0.1–56 μM) and in the cisplatin-resistant A2780cis cells. Paradoxically, phen and dmb as well as their half-sandwich Rh complexes showed increased toxicity against multidrug resistant MES-SA/Dx5 cells. In contrast, coordination to Ru caused loss of toxicity. Solution equilibrium constants showed that the studied metal complexes have high stability, and no dissociation was found for Ru and Rh complexes even at micromolar concentrations in a wide pH range. However, in the case of Ru complexes a slow and irreversible decomposition, namely arene loss, was also observed, which was more pronounced in light exposure in aqueous solution. In the case of neo, the methyl groups next to the nitrogen atoms significantly decrease the stability of complexes. For Rh complexes, the order of the stability constants corrected with ligand basicity (log K*): 9.78 (phen) > 9.01 (dmb) > 8.89 (bpy) > 3.93 (neo). The coordinated neo resulted in an enormous decrease in the chloride ion affinity of Ru compounds. Based on the results, a universal model was introduced for the prediction of chloride ion capability of half-sandwich Rh and Ru complexes. It combines the effects of the bidentate ligand and the M(arene) part using only two terms, performing multilinear regression procedure.

Rhodium (Rh) single-atom catalysts (SACs) supported on activated carbon (Rh1/AC) are prepared via a “top-down” chemical reaction-induced dispersion process using Rh nanoparticles as the starting materials. The as-obtained Rh1/AC exhibits hydrogen evolution activity and stability much better than those of the state-of-the-art Pt/C catalysts in alkaline solutions.

Two model porphyrin metal-organic frameworks were used for the incorporation of Rh(i) species by a post-synthetic metallation under mild conditions. As a result, new rhodium MOFs (Rh/MOFs), Rh/PCN-222 and Rh/NU-1102, were synthesized and structurally characterized. To illustrate the potential of this catalytic platform, we use Rh/MOFs as phosphine-free heterogeneous catalysts in the hydrogenation of unsaturated hydrocarbons under mild reaction conditions (30 °C and 1 atm H2). We found that for our Rh/MOFs an activation step is required during the first run of the catalytic process. The presence of Rh-CO moieties allowed us to monitor the activation pathway of the catalyst under a H2 atmosphere, by in situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). After activation, the catalyst remains highly active during the subsequent catalytic cycles. This simple post-synthetic modification approach presents new possibilities for the utilization of Rh-based catalytic systems with robust porphyrin-based MOFs as supports.

By virtue of α-allenols as innovative three-carbon annulation components, the Rh(III)-catalyzed redox-neutral C-H coupling of N-phenoxyacetamides with α-allenols has been realized for the assembly of 4-alkylidene chroman-2-ol frameworks via an unusual [3+3] annulation. This transformation features good functional group tolerance, specific regio-/chemoselectivity and potential synthetic utility. Mechanistic studies reveal that synergistic coordination modes between the dual directing groups (-ONHAc and -OH) and the rhodium metal center account for the observed exclusive selectivity.

Chloride poisoning is a serious problem for the electrocatalytic reduction of aqueous nitrate (NO3−) and improved electrocatalysts are needed. Here we study the electrocatalytic activity of rhodium sulfide supported on carbon (RhxSy/C) for the reduction of nitrate and compare it against Pt/C and Rh/C in the presence of chloride. Between 0.05–0.15 V vs. RHE, RhxSy/C has a steady-state nitrate reduction current density in 1 M H2SO4 + 1 M NaNO3 that is 1.6–5.6 times greater than Rh/C (the most active metal electrocatalyst) and 10–24 times greater than Pt/C. Current densities are decreased by 37% for RhxSy/C, 62% for Rh/C, and 40% for Pt/C at 0.1 V vs. RHE in the presence of 1 mM chloride. The decrease in nitrate reduction activity for Pt, Rh, and RhxSy is due to the competitive adsorption of chloride and nitrate on the surface. Density functional theory (DFT) modeling predicts that chloride poisoning will persistently inhibit nitrate reduction on metals due to linear adsorbate scaling relations between nitrate and chloride. DFT calculations and microkinetic modeling of our experimental measurements predict that nitrate converts to nitrite via an H-assisted dissociation mechanism on Pt and direct nitrate dissociation on Rh and RhxSy. Pristine RhxSy (i.e., Rh3S4, Rh2S3, and Rh17S15) terraces are predicted to be inactive toward nitrate reduction. In contrast, sulfur vacancies in Rh3S4 terraces are predicted to be active for nitrate reduction, but also bind chloride strongly. Thus, sulfur-defected Rh3S4 rationalize the experimentally observed high activity but moderate chloride poison-resistance of RhxSy/C for nitrate reduction.

Divergent catalytic reactions provide access to diverse nitrogen-containing heterocycles through controlled catalysts. This study presents a computational study of rhodium- and cobalt-catalyzed decarboxylative transformations of isoxazolones. The calculations clarified the mechanistic details of the reaction and the origins of the catalyst controlled product selectivity. We identified a mechanism in which alkene insertion precedes CO2 elimination in rhodium- and cobalt-catalyzed decarboxylative transformations of isoxazolones. The kinetic feasibility of this mechanism is attributed to the avoidance of formation of a highly unstable four-membered rhodacycle intermediate. The reason for the formation of different products with the two metals lies in the different geometries of the metal centers in the key transition states. The energy barrier of C–N-bond-forming reductive elimination via the triplet state for the cobalt system is small because the distorted trigonal–bipyramidal coordination geometry of the transition state maximizes the overlap between the π* orbital of the N atom and the σ* orbital of the C atom.

The synthesis and reactivity of the bimetallic rhodium–copper complex, Rh(COE)[P2N2]Cu, which is stabilized by the P2N2 macrocycle, is reported. In the solid state, the rhodium and copper centers are on opposite sides of the macrocyclic ring with the Cu(I) in a linear environment and the Rh(I) in a square planar array. However, in solution a very symmetrical structure is suggested on the basis of the 1H NMR data, which is consistent with at least two separate fluxional processes, rotation of the cyclooctene unit and movement of the Rh(I) unit between the two amido donors. Addition of H2 to Rh(COE)[P2N2]Cu results in the formation of ([P2N2H]RhH(μ-H)2Cu)2 via hydrogenation of the coordinated cyclooctene unit, oxidative addition of H2 to the rhodium center and hydrogenolysis of the copper amido unit. Monitoring the reaction of H2 by NMR spectroscopy indicated the formation of a number of intermediates which suggests hydrogenolysis of the copper amido linkage occurs to generate CuH in some form, along with Rh(COE)[P2N2H], which is converted to Rh(H)2[P2N2H] by hydrogenation of the cyclooctene, which then recombines with the CuH present to generate the final product. Deuteration studies indicate that there is considerable H/D scrambling in the cyclooctane produced that we attribute to reversible beta-elimination, migratory insertion steps.

Titanium dioxide (TiO2) has been widely studied because of its stable chemical properties, low cost and non-toxicity. But some of its shortcomings also limit its development, such as a large band gap and weak catalytic ability under visible light. The photocatalytic performance of titanium dioxide has been improved by doping nonmetal boron (B) and noble metal rhodium (Rh) in the current study. In general, a metal's electron-deficient state can be regarded as the active sites in a hydrogen evolution reaction. The electron-deficient state of Rhδ+ contributes to its high ability to grab electrons. The light absorption range of Rh nanoparticles (NPs) can reach the visible light band. TiO2 with special morphology is synthesized by a one-step hydrothermal method, and B-doped titanium dioxide with an oxygen vacancy is obtained by adding a B source into the precursor solution. The influence of nonmetal ion doping on oxygen vacancy is studied. The Rh/B–TiO2-550 photocatalyst is synthesized by depositing Rh NPs onto B–TiO2, and the bifunctional photocatalyst with a visible light response is successfully prepared. The Rh/B–TiO2-550 catalyst shows good performance in the degradation of hydrogen and pollutants produced in the photocatalytic decomposition process. Under the irradiation of a 300 W xenon lamp, the hydrogen production reaches 108.67 μmol in 3 h, and the degradation effect of OPP reaches 99.48%.

Having recently reported on the synthesis and rhodium complexes of the novel macrocyclic pincer ligand PNP-14, which is derived from lutidine and features terminal phosphine donors trans-substituted with a tetradecamethylene linker (Dalton Trans., 2020, 49, 2077–2086 and Dalton Trans., 2020, 49, 16649–16652), we herein describe our findings critically examining the chemistry of iridium homologues. The five-coordinate iridium(I) and iridium(III) complexes [Ir(PNP-14)(η2:η2-cyclooctadiene)][BArF4] and [Ir(PNP-14)(2,2′-biphenyl)][BArF4] are readily prepared and shown to be effective precursors for the generation of iridium(III) dihydride dihydrogen, iridium(I) bis(ethylene), and iridium(I) carbonyl derivatives that highlight important periodic trends by comparison to rhodium counterparts. Reaction of [Ir(PNP-14)H2(H2)][BArF4] with 3,3-dimethylbutene induced triple C–H bond activation of the methylene chain, yielding an iridium(III) allyl hydride derivative [Ir(PNP-14*)H][BArF4], whilst catalytic homocoupling of 3,3-dimethylbutyne into Z-tBuC[triple bond, length as m-dash]CCHCHtBu could be promoted at RT by [Ir(PNP-14)(η2:η2-cyclooctadiene)][BArF4] (TOFinitial = 28 h−1). The mechanism of the latter is proposed to involve formation and direct reaction of a vinylidene derivative with HC[triple bond, length as m-dash]CtBu outside of the macrocyclic ring and this suggestion is supported experimentally by isolation and crystallographic characterisation of a catalyst deactivation product.\ud \ud

A novel protocol for Rh(iii)-catalyzed switchable C-H acylmethylation and annulation of 2,2'-bipyridine derivatives with sulfoxonium ylides is reported. This protocol provides a facile approach to synthesize structurally diverse acylmethylated 2,2'-bipyridine derivatives and acyl pyrido[2,3-a]indolizines with a broad range of functional group tolerance.

A new method for the direct and stereoselective synthesis of 3-substituted isoindolinones via Rh(III)-catalyzed chiral N-sulfinyl amide directed asymmetric [4 + 1] annulation of benzamides with acrylic esters has been developed. The reaction proceeded through an oxidative C–H olefination and a subsequent cyclization by intramolecular aza-Michael addition, producing a series of diastereoisomeric chiral isoindolinones (20 examples) in generally good yields with a dr value up to 5.5 : 1. The absolute configurations of the newly formed C-stereocenters in the major and minor diastereomers of the catalysis product have been determined by X-ray crystal diffraction analysis to be S and R, respectively. The separation of the major diastereoisomers from the catalysis products and subsequent removal of the N-sulfinyl chiral auxiliary afforded enantiomerically pure (S)-isoindolinones. The application of the obtained (S)-isoindolinones in the synthesis of several biologically active isoindolinones such as (S)-PD172938, (S)-pazinaclone and (S)-pagoclone is presented.

Over the past few decades, the landscape of inorganic medicinal chemistry has been dominated by investigations on platinum or ruthenium, while the research based on other metal centers such as rhodium has been relatively insufficient. In this work, a series of cyclometalated rhodium(iii) complexes with imidazo[4,5-f][1,10]phenanthroline containing different aromatic rings were synthesized and characterized. Notably, all the complexes displayed stronger anticancer activity against various cancer cells compared with cisplatin. A mechanism study revealed that the rhodium complexes accumulated in the mitochondria, elevated the levels of mitochondrial reactive oxygen species (ROS) and released cytochrome c, indicating severe mitochondrial damage during the anticancer activity. Further studies illustrated that the rhodium complexes caused cell cycle arrest at the G2/M phase, upregulated the expression of p53 and reduced the ratio of B-cell lymphoma-2 (Bcl-2)/Bcl-2-associated x (Bax), which ultimately resulted in cellular apoptosis. Overall, through mitochondrial pathways, these Rh(iii) complexes could induce cellular apoptosis to a larger extent than cisplatin and should be paid close attention as promising chemotherapeutic drugs in anticancer research.

Arylation is a common behaviour in organic synthesis for the construction of complex structures, especially the biaryls. Among those reported arylation procedures, transition-metal-catalyzed direct C(sp2)-H arylation has been rapidly developed in recent decades and has become a reliable alternative to traditional cross-coupling procedures using organometallic reagents. Great achievements in rhodium-catalyzed C(sp2)-H arylation have been witnessed during the last decade. Aryl halides, simple arenes, aryl boronic acids, arylsilanes, aryl aldehyde, aryl carboxylic acid, diazides, etc. were successfully utilized as arylating reagents under rhodium-catalyzed conditions. In this review, recent achievements in rhodium-catalyzed arylations through C(sp2)-H bond activation were summarized together with the mechanism discussions.

A facile synthesis of multi-functionalized benzothiazonine was achieved by the rhodium-catalyzed denitrogenative annulation of 1-sulfonyl-1,2,3-triazole and thiochromone. In view of the excellent atom economy, broad substrate scope and easy availability of starting materials, the protocol provided an efficient strategy for the construction of medium N,S-heterocycles.

Herein we report a [Cp*RhCl2]2-catalyzed coupling cyclization of two different classes of allenes with 2,3-allenoic acids affording 2(5H)-furanone skeletons of products and 2,3-allenols forming a conjugated (E)-enal or enone functionality to the β-position of the 2(5H)-furanones. These products are important building blocks for the syntheses of potentially bioactive compounds. The reaction proceeded via the nucleometalation, insertion, and stereodefined 1,4-H delivery carried by rhodium.

Three chiral dirhodium coordination polymers Rh2–Ln (n = 1–3) have been synthesized via ligand exchange between dirhodium trifluoroacetate Rh2(TFA)4 and differently sized chiral dicarboxylic acids derived from L-tert-leucine. SEM images indicate that the Rh2–Ln (n = 1–3) polymers have a lamellar structure. XPS data demonstrate that the oxidation state of rhodium in the dirhodium nodes is maintained during the synthesis of the polymers. The coordination polymers have been further characterized by FTIR, 1H → 13C CP MAS NMR and 19F MAS NMR spectroscopy to prove the formation of polymers via ligand exchange. Although the quantitative 19F MAS NMR spectra reveal incomplete ligand substitution in the coordination polymers, these catalysts show excellent activity and selectivity in the asymmetric cyclopropanation reaction between styrene and diazooxindole. In particular, the enantioselectivity has been significantly improved compared with previously designed dirhodium coordination polymers, which were synthesized from aromatic dicarboxylic acids derived from L-phenylalanine. Meanwhile, the dirhodium polymers can be easily recycled five times without significant reduction in their catalytic efficiency.

A concise approach for the synthesis of structurally diverse indoles enabled by RhIII-catalyzed switchable C2 C–H olefination and alkylation of N-quinolinyl indoles with alkenes as well as highly efficient C–H deuteration is described. The reaction can be conducted under practical reaction conditions, with a broad substrate scope and good tolerance of various functional groups. The potential value of this synthetic methodology is shown by the diverse late-stage modification of the products, thereby providing a straightforward route to access functionalized indoles, especially indole-based P,N ligands.

A highly efficient homogeneous catalyst system for production of CH3OH from CO2 using single molecular defined ruthenium and rhodium RAPTA-type catalysts [Ru(η6-p-cymene)X2(PTA)] (X = I(1), Cl(2); PTA = 1,3,5-triaza-7-phosphaadamantane) and rhodium catalysts [Rh(η5-C5Me5)X2(PTA/PTA-BH3)] (X = Cl(3), H(4) and PTA-BH3, H(5)) developed in acidic media under mild conditions. A TON of 4752 is achieved using a [Ru(η6-p-cymene)I2(PTA)] catalyst which represents the first example of CO2 hydrogenation to CH3OH using single molecular defined Ru and Rh RAPTA-type catalysts.

A new family of rhodium porphyrin complexes bearing a primary, secondary or benzylic perfluoroalkyl ligand RhIII(btpp)RF [btpp = 5,10,15,20-tetrakis(4-tert-butylphenyl)porphyrinato dianion] has been successfully synthesized in good yields using commercially available perfluoroalkyl iodides RFI (RF = nC3F7, iC3F7, nC4F9, nC6F13, cC6F11, nC10F21 and C6F5CF2) and the air-stable precursor RhIII(btpp)Cl under basic conditions. Mechanistic investigations suggest a halogen atom transfer pathway with a rhodium(ii) porphyrin metalloradical.

Rh(III)-Catalyzed enone carbonyl directed annulative coupling of α-aroyl ketene dithioacetals and diazo compounds has been realized via aryl and olefinic C–H bond activation. This transformation offers highly functionalized indanone derivatives bearing a quaternary carbon stereocenter at the β-position. The protocol exhibits high efficiency, broad substrate scope, and high compatibility with functional groups.

Electrochemical reduction of nitrogen to ammonia has received considerable attention for sustainable nitrogen fixation, but the sluggish kinetics results in unsatisfactory activity and efficiency. Designing electrocatalytic active centers for nitrogen adsorption and activation is highly desired. Herein, we present an electrodeposition method for the synthesis of a phosphorus-doped mesoporous rhodium film on nickel foam for the electrochemical synthesis of ammonia. Due to the unique combination of components and structure, the obtained catalyst not only shows excellent catalytic performance (NH3 yield: 32.57 μg h-1 mg-1cat.; faradaic efficiency: 40.86%), but also exhibits almost no decrease in activity after the durability test. This research work can provide a facile synthesis strategy for non-metal-doped porous metal based catalysts, which would be promising for the electrochemical synthesis of ammonia.

Alkyl cyclohexanes were synthesized in high selectivity via a combined hydrogenation/hydrodeoxygenation of aromatic ketones using ligand-free RhCl3 as pre-catalyst in trifluoroethanol as solvent. The true catalyst consists of rhodium nanoparticles (Rh NPs), generated in situ during the reaction. A range of conjugated as well as non-conjugated aromatic ketones were directly hydrodeoxygenated to the corresponding saturated cyclohexane derivatives at relatively mild conditions. The solvent was found to be the determining factor to switch the selectivity of the ketone hydrogenation. Cyclohexyl alkyl-alcohols were the products using water as a solvent.

The kinetic resolution of 2-aryl tetrahydro-4-quinolone derivatives was efficiently achieved by rhodium-catalysed asymmetric transfer hydrogenation using HCO2H/DABCO as the hydrogen source. The reaction afforded the enantiomerically enriched 2-aryl-2,3-dihydroquinolin-4(1H)-ones with excellent levels of enantioselectivity (up to >99% ee) as well as the corresponding synthetically useful enantiomerically enriched 2-aryl tetrahydro-4-quinolols in high isolated yields and up to >99% enantioselectivity with high selectivity factors (s up to 1057).

The rhodium(III)-catalyzed spiroannulation reaction between N-aryl indazol-3-ols and maleimides is described herein. The developed method is showcased by the construction of spirosuccinimides using bioactive molecule-linked and chemical probe-linked maleimides. Combined mechanistic investigations including the determination of an isolable rhodacycle complex aided the elucidation of a plausible reaction mechanism.

An efficient asymmetric hydrogenation of cyclic tetrasubstituted-olefinic dehydroamino acid derivatives has been achieved with a Rh-ArcPhos catalyst, affording a series of α-acylamino-β-alkyl tetrahydropyranones with two contiguous chiral centers in up to 96% ee and 1000 TON.