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Kalmanol, the flagship member of the kalmane diterpene family, possesses a complex and highly oxidized 5/5/8/5 tetracyclic skeleton with nine contiguous stereocenters and exhibits significant analgesic effects and cardiotoxic properties. We have achieved the efficient total synthesis of (+)-kalmanol in 22 steps with 2.3 % yield. The synthesis featured a Rh-catalyzed [5+2+1] cycloaddition reaction to construct 5/5/8 tricyclic skeleton, and a meticulously designed sequence of stereoselective oxidations of the 5/5/8/5 tetracyclic skeleton., (© 2024 Wiley-VCH GmbH.)

Starting from N-acyl sulfonimidamides, mechanochemically generated rhodium nitrenoids undergo intramolecular N-O couplings to provide unprecedented 1,3,2,4-oxathiadiazole 3-oxides in good to excellent yields. The cyclization proceeds efficiently with a catalyst loading of only 0.5 mol% in the presence of phenyliodine(III) diacetate (PIDA) as oxidant. Neither an inert atmosphere nor additional heating is required in this solvent-free procedure. Under heat or blue light, the newly formed five-membered heterocycles function as nitrene precursors reacting with sulfoxides as exemplified by the imidation of dimethyl sulfoxide., (© 2024 Wiley‐VCH GmbH.)

We report here the rhodium catalyzed reductive hydroformylation of methyl 10-undecenoate. Our approach is based on an ionic liquid/heptane biphasic system associated with commercially available trialkylamines. The effects of various reaction parameters such as amine type, amine amount, temperature, syngas pressure and composition were studied in order to minimize the rhodium leaching and increase the production of primary alcohols. Although the amine is less soluble in the ionic liquid than in heptane, the catalytic system is efficiently maintained in the ionic liquid phase. For the optimized conditions, the catalytic ionic liquid layer can be recycled at least nine times by keeping an alcohol yield over 50% and by limiting the rhodium leaching. As an extension of this system and to examine the long-term stability, this batch system was transferred to a miniplant for a continuous flow process. A pilot plant was operated for 45 h of total reaction time, reaching a TTON of 232 for alcohol production., (© 2024 Wiley‐VCH GmbH.)

We have developed the Rh-catalyzed enantioselective [2+2+2] cycloaddition of homopropargyl enamides (tosylamide-tethered 1,6-enynes) with alkynes to construct tetrahydroindole skeletons found in natural alkaloids and pharmaceuticals. This cycloaddition proceeds at room temperature in high yields and regio- and enantioselectivity with a broad substrate scope. The preparative scale reaction followed by substituent conversion on the nitrogen atom and the diastereoselective [4+2] cycloaddition with singlet O 2 affords hexahydroindole-diols bearing three stereogenic centers and variable substituents on the nitrogen. Mechanistic studies have revealed that the substituents of the enynes change the ratio of intramolecular and intermolecular rhodacycle formation when using terminal alkynes, varying the ee values of the cycloadducts., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Tryptophan and its non-canonical variants play critical roles in pharmaceutical molecules and enzymes. Facile access to this privileged class of amino acids from readily available building blocks remains a long-standing challenge. Here, we report a regioselective synthesis of non-canonical tryptophans bearing C4-C7 substituents via Rh-catalyzed annulation between structurally diverse tert-butyloxycarbonyl (Boc)-protected anilines and alkynyl chlorides readily prepared from amino acid building blocks. This transformation harnesses Boc-directed C-H metalation and demetalation to afford a wide range of C2-unsubstituted indole products in a redox-neutral fashion. This umpolung approach compared to the classic Larock indole synthesis offers a novel mechanism for heteroarene annulation and will be useful for the synthesis of natural products and drug molecules containing non-canonical tryptophan residues in a highly regioselective manner., (© 2024 Wiley‐VCH GmbH.)

Rhodium complexes in the -I and 0 oxidation states are of great potential interest in catalytic applications. In contrast to their rhodium +I congeners, however, the structural and electronic parameters governing their access and stability are far less understood. Herein, we investigate the two-electron reduction of a parameterized series of bis(diphosphine) Rh complexes [Rh(dxpy) 2 ]NTf 2 (x=P-substituent, y=alkanediyl bridging P atoms). Through (electro)reductions from the Rh I parents, Rh -I d 10 -complexes were obtained and characterized spectroscopically, including 103 Rh NMR data. The reductive steps convolute with structural rearrangements from square planar to tetrahedral coordination. We found that the extent of these reorganisations defines whether the first E 0 (Rh I/0 ) and second E 0 (Rh 0/-I ) reduction potentials are normally ordered, leading to monoelectronic stepwise transitions, or inverted, giving bielectronic events. Reductionist approaches based on Hammett parameters or the P-Rh-P bite angles provide only partial correlations with the redox potentials. However, we identified the C-O stretch of analogue diphosphine complexes as an expedient computational parameter that enables these correlations through both electronic and geometric features, even in a predictive manner. Gaining control over two-electron reduction behaviors through rationalized ligand effects has potential impact beyond Rh complexes, for molecular and enzymatic metal sites commonly exhibiting bielectronic transitions., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Supported metal single atom catalysis is a dynamic research area in catalysis science combining the advantages of homogeneous and heterogeneous catalysis. Understanding the interactions between metal single atoms and the support constitutes a challenge facing the development of such catalysts, since these interactions are essential in optimizing the catalytic performance. For conventional carbon supports, two types of surfaces can contribute to single atom stabilization: the basal planes and the prismatic surface; both of which can be decorated by defects and surface oxygen groups. To date, most studies on carbon-supported single atom catalysts focused on nitrogen-doped carbons, which, unlike classic carbon materials, have a fairly well-defined chemical environment. Herein we report the synthesis, characterization and modeling of rhodium single atom catalysts supported on carbon materials presenting distinct concentrations of surface oxygen groups and basal/prismatic surface area. The influence of these parameters on the speciation of the Rh species, their coordination and ultimately on their catalytic performance in hydrogenation and hydroformylation reactions is analyzed. The results obtained show that catalysis itself is an interesting tool for the fine characterization of these materials, for which the detection of small quantities of metal clusters remains a challenge, even when combining several cutting-edge analytical methods., (© 2024 Wiley-VCH GmbH.)

NMR spectroscopy studies using parahydrogen-induced polarization have previously established the existence of the pairwise hydrogen addition route in the hydrogenation of unsaturated hydrocarbons over heterogeneous catalysts, including those based on rhodium (Rh 0 ). This pathway requires the incorporation of both hydrogen atoms from one hydrogen molecule to the same product molecule. However, the underlying mechanism for such pairwise hydrogen addition must be better understood. The involvement of carbon, either in the form of carbonaceous deposits on the surface of a catalyst or as a metal carbide phase, is known to modify catalytic properties significantly and thus could also affect the pairwise hydrogen addition route. Here, we explored carbon's role by studying the hydrogenation of propene and propyne with parahydrogen on a Rh 2 C catalyst and comparing the results with those for a Rh 0 /C catalyst obtained from Rh 2 C via H 2 pretreatment. While the catalysts Rh 2 C and Rh 0 /C differ notably in the rate of conversion of parahydrogen to normal hydrogen as well as in terms of hydrogenation activity, our findings suggest that the carbide phase does not play a significant role in the pairwise H 2 addition route on rhodium catalysts., (© 2024 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

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., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

Chemical wave patterns and V-oxide redistribution in catalytic methanol oxidation on a VO x /Rh(110) surface have been investigated in the 10 -4  mbar range with low-energy electron microscopy (LEEM) and micro spot low-energy electron diffraction (micro-LEED) as in situ methods. V coverages of θ V =0.2 and 0.4 MLE (monolayer equivalents) were studied. Pulses display a c(2×2) pattern in the reduced part and (1×2) and c(2×8) structures in the oxidized part of the surface. At θ V =0.4 MLE (1×2)/(1×4) patterns with streaks along the [001]-direction at the 1/8 positions are present on the oxidized part of the surface. This phase can be assigned to V-oxide. On a tentative basis, an excitation mechanism for pulses is presented, Annealing the surface to 990 K under reaction conditions results in a macroscopic hole pattern in which holes of low VO x coverage are surrounded by a V-oxide layer. Chemical waves propagate inside the holes as well as on the VO x covered parts of the surface. The results demonstrate for the first time that also in supported oxidic overlayers selforganization processes can take place leading to chemical waves and a large scale redistribution of the oxide., (© 2024 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

We report herein of a novel, enantioselective and rhodium- catalyzed cyclisation of allenyl alcohols towards chiral α-vinylic, cyclic ethers employing a rhodium/(R,R)-Me-ferrocelane catalyst. The corresponding chiral cyclic products were obtained in general high yields and enantioselectivities. The synthetic value of our obtained products was further exemplified by transformations of the allylic ether function. Furthermore, applying our newly developed method in our previously reported route towards the total synthesis of (R,R,R)-α-tocopherol, we accomplished a significantly improved 2 nd generation synthesis of the chromane building providing a total number of 13 steps and an overall total yield of 27 %., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Isoindolinones are vital heterocyclic compounds in medicinal chemistry, notable for their diverse bioactivities. Significant attention has been devoted to their preparation; however, existing methods are unsuitable for constructing unsubstituted 3-methyleneisoindolin-1-ones. Herein, we present a rhodium(III)-catalyzed method for synthesizing unsubstituted 3-methyleneisoindolin-1-ones via C-H/N-H activation and annulation of N-methoxybenzamides with potassium (ethenyl)trifluoroborate. This approach offers mild reaction conditions, high regioselectivity, and efficient yields. Interestingly, sterically demanding or heterocyclic N-methoxyaromaticamides resulted in the formation of 2-vinyl(hetero)aromatic amides instead of 3-methyleneisoindolin-1-ones. Mechanistic insights suggest a rhodacycle intermediate pathway, highlighting the method's potential for developing new bioactive isoindolinone derivatives., (© 2024 Wiley-VCH GmbH.)

Development of chiral indenyl ligands for asymmetric C-H activation is a longstanding challenge, and extremely few successes have been achieved. In this paper, we describe a class of readily accessible, facilely tunable and user-friendly chiral indenyl ligands featuring a [2.2]benzoindenophane skeleton via a divergent synthesis strategy. The corresponding chiral indenyl rhodium catalysts were successfully applied in the asymmetric C-H activation reaction of O-Boc hydroxybenzamide with alkenes to give various chiral dihydroisoquinolone products (up to 97 % yield, up to 98 % ee). Moreover, the asymmetric C-H activation reaction of carboxylic acids with alkynes was also successfully accomplished, providing a range of axially chiral isocoumarins (up to 99 % yield, up to 94 % ee). Notably, this represents the first example of enantioselective transition metal catalyzed C(sp 2 )-H activation/oxidative coupling of benzoic acids with internal alkynes to construct isocoumarins. Given many attractive features of this class of indenyl ligands, such as convenient synthesis, high tunability and exclusive face-selectivity of coordination, its applications in more catalytic asymmetric C-H activation and in other asymmetric catalysis are foreseen., (© 2024 Wiley-VCH GmbH.)

A new, cationic N -heterocyclic carbene Rh I complex with a tetra-fluorido-borate counter-anion, [Rh(C 8 H 12 )(C 8 H 15 N 3 )(C 18 H 15 P)]BF 4 , 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 Rh I 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 inter-actions between the ions. One of the tetra-fluorido-borate anions shows statistical disorder of the F atoms., (© Lerch et al. 2024.)

A new neutral triazole-based N-heterocyclic carbene rhodium(I) complex [RhCl(C 8 H 12 )(C 8 H 15 N 3 )], has been synthesized and structurally characterized. The complex crystallizes with two mol-ecules in the asymmetric unit. The central rhodium(I) atom has a distorted square-planar coordination environment, formed by a cyclo-octa-1,5-diene (COD) ligand, an N-heterocyclic carbene (NHC) ligand, and a chlorido ligand. The bond lengths are unexceptional. A weak inter-molecular non-standard hydrogen-bonding inter-action exists between the chlorido and NHC ligands., (© Lerch et al. 2024.)

The κ 2 -(P,N)-phosphine ligand precursor NH(CH 2 CH 2 PCy 2 ) 2 can be used for the synthesis of the rhodium(I) complex [Rh(CO){ĸ 3 -(P,N,P)-Cy 2 PC 2 H 4 NHC 2 H 4 PCy 2 }][Cl] (1). The deprotonated complex [Rh(CO){ĸ 3 -(P,N,P)-Cy 2 PC 2 H 4 NC 2 H 4 PCy 2 }] (2) shows a cooperative reactivity of the PNP ligand in the activation reaction of SO 2 F 2 to yield the rhodium fluorido complex trans-[Rh(F)(CO){ĸ 2 -(P,P)-Cy 2 PC 2 H 4 N(SO 2 F)C 2 H 4 PCy 2 }] 2 (3) by S-F bond cleavage. It is remarkable that no reaction was observed when 3 was treated with hydrogen sources e. g. dihydrogen, organosilicon compounds such as triethylsilane or TMS-CF 3 and different fluorine sources such as SF 4 or Selectfluor®. However, the treatment of complex 3 with XeF 2 in the presence of CsF resulted in the formation of the unique fluorido rhodium(III) complex cis,trans-[Rh(F) 3 (CO){ĸ 2 -(P,P)-Cy 2 PC 2 H 4 N(SO 2 F)C 2 H 4 PCy 2 }] 2 (4). In the presence of pyridine(HF) X or BF 3 the fluorido complex 3 converted into the dicationic complexes [Rh(CO){ĸ 2 -(P,P)-Cy 2 PC 2 H 4 N(SO 2 F)C 2 H 4 PCy 2 }] 2 [XF] 2 , X=HF (5) or BF 3 (6), respectively., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Transition-metal-catalyzed enantioselective transformations of aryl/aryl carbene are inherently challenging due to the difficulty in distinguishing between two arene rings in the reaction process thus remain largely less explored. The few successful examples reported so far, without exception, have all been catalyzed by Rh(II)-complexes. Herein, we describe our successful development of a novel cationic Rh(I)/chiral diene catalytic system capable of efficient enantioselective B-H and O-H insertions with diaryl diazomethanes, allowing the access to a broad range of gem-diarylmethine boranes and gem-diarylmethine ethers in good yields with high enantioselectivities. Notably, previously unattainable asymmetric diarylcarbene insertion into the O-H bond was achieved for the first time. A remarkable feature of this newly designed Rh(I)/diene catalyst bearing two ortho-amidophenyl substitutents is that it can distinguish between two arene rings of the diaryl carbene through a stereochemically selective control of π-π stacking interactions. DFT calculations indicate that the rotation-restricted conformation of Rh(I)/diene complex played an important role in the highly enantioselective carbene transformations. This work provides an interesting and unprecedented stereocontrol mode in diaryl metal carbene transformations., (© 2024 Wiley‐VCH GmbH.)

Rh(III) and Ru(II) complexes, [RhCl 2 (κ 4 -N 2 N'P-L)][SbF 6 ] (1) and [RuCl 2 (κ 4 -N 2 N'P-L)] (2), were synthesised using the tetradentate ligand L (L=N,N-bis[(pyridin-2-yl)methyl]-[2-(diphenylphosphino)phenyl]methanamine). In each case only one diastereomer is detected, featuring cis-disposed pyridine groups. The chloride ligand trans to pyridine can be selectively abstracted by AgSbF 6 , with the ruthenium complex (2) reacting more readily at room temperature compared to the rhodium complex (1) which requires elevated temperatures. Rhodium complexes avoid the second chloride abstraction, whereas ruthenium complexes can form the chiral bisacetonitrile complex [Ru(κ 4 -N 2 N'P-L)(NCMe) 2 ][SbF 6 ] 2 (5) upon corresponding treatment with AgSbF 6 . The complex [RhCl 2 (κ 4 -N 2 N'P-L)][SbF 6 ] (1) has also been used to synthesise polymetallic species, such as the tetrametallic complex [{RhCl 2 (κ 4 -N 2 N'P-L)} 2 (μ-Ag) 2 ][SbF 6 ] 4 (6) which was formed with complete diastereoselectivity and chiral molecular self-recognition. In addition, a stable bimetallic mixed-valence complex [{Rh(κ 4 -N 2 N'P-L)}{Rh(COD)}(μ-Cl) 2 ][SbF 6 ] 2 (7) (COD=cyclooctadiene) was synthesised. These results highlight the significant differences in chloride lability between Rh 3+ and Ru 2+ complexes and demonstrate the potential for complexes to act as catalyst precursors and ligands in further chemistry applications., (© 2024 The Authors. ChemPlusChem published by Wiley-VCH GmbH.)

The paddlewheel-type dimetal core ([M 2 ]) is a ubiquitous motif in the nodes in coordination polymers (CPs) and metal-organic frameworks (MOFs). However, their preparation has relied on ligand-substitution-labile metal ions owing to challenges associated with crystallization. Consequently, examples featuring ligand-substitution-inert metal ions, such as Ru or Rh, are scarce. This study presents the synthesis of novel reticular imine-linked CPs incorporating the paddlewheel-type diruthenium(II, II) ([Ru 2 II,II ]; 1-Ru) or dirhodium(II, II) ([Rh 2 II,II ]; 1-Rh) subunits. The synthetic approach involved a Schiff base dehydration condensation reaction between p-formylbenzoate-bridged [Ru 2 II,II ] or [Rh 2 II,II ] precursors (i. e., CHO-Ru and CHO-Rh, respectively) and 2,5-dimethyl-1,4-phenylenediamine in a 1 : 2 ratio. The catalytic activities of 1-Ru and 1-Rh for the photochemical reduction of CO 2 in a heterogeneous system depended on the metal site. The 1-Ru system exhibited exceptional selectivity, generating 3.0×10 4  μmol g -1 of CO after 24 h of irradiation, whereas the 1-Rh system generated a lower amount of CO (3.2×10 3  μmol g -1 ). The catalytic activity of 1-Ru ranked with that of all relevant catalytic systems. This study paves the way for the exploration of [Ru 2 II,II ]- or [Rh 2 II,II ]-based polymers with open metal site-dependent functional properties., (© 2024 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

The catalytic access of silicon-stereogenic organosilanes remains a big challenge, and largely depends on the desymmetrization of the symmetric precursors with two identical substitutes attached to silicon atom. Here we report the construction of silicon-stereogenic organosilanes via catalytic kinetic resolution of racemic monohydrosilanes with good to excellent selectivity factors. Both Si-stereogenic dihydrobenzosiloles and Si-stereogenic monohydrosilanes could be efficiently accessed in one single operation via Rh-catalyzed enantioselective intramolecular hydrosilylation, employing (R,R)-Et-DuPhos as the optimal ligand. This catalytic protocol features mild conditions, a low catalyst loading (0.1 mol % [Rh(cod)Cl] 2 ), high stereoinduction (S factor up to 152), and excellent scalability. Moreover, further derivatizations led to the efficient synthesis of uncommon middle-size (7- and 8-membered) Si-stereogenic silacycles. Preliminary mechanistic study indicates this reaction might undergo a modified Chalk-Harrod mechanism., (© 2024 Wiley-VCH GmbH.)

A carbon-rich molecule is synthesized, which mainly contains conjugated sp 2 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 Rh I ─Rh I bond. Furthermore, CH units are placed in proximity to the metal centers. The dicationic complex [Rh 2 (bipy) 2 {Ph 2 Ptrop (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., (© 2024 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

Organophosphorus nerve agents (OPNAs) pose a great threat to humanity. Possessing extreme toxicity, rapid lethality, and an unassuming appearance, these chemical warfare agents must be quickly and selectively identified so that treatment can be administered to those affected. Chromogenic detection is the most convenient form of OPNA detection, but current methods suffer from false positives. Here, nitrogenous base adducts of dirhodium(II,II) acetate were synthesized and used as chromogenic detectors of diethyl chlorophosphate (DCP), an OPNA simulant. UV-vis spectrophotometry was used to evaluate the sensitivity and selectivity of the complexes in the detection of DCP. Visual limits of detection (LOD) for DCP were as low as 1.5 mM DCP, while UV-vis-based LODs were as low as 0.113 μM. The dirhodium(II,II) complexes were also tested with several potential interferents, none of which produced a visual color change that could be mistaken for OPNA response. Ultimately, the Rh 2 (OAc) 4 (1,8-diazabicyclo[5.4.0]undec-7-ene) 2 complex showed the best combination of detection capability and interferent resistance. These results, when taken together, show that dirhodium(II,II) paddlewheel complexes with nitrogenous base adducts can produce instant, selective, and sensitive detection of DCP. It is our aim to further explore and apply this new motif to produce even more capable OPNA sensors.

Coenzyme B 12 (AdoCbl; 5'-deoxy-5'-adenosylcobalamin), the quintessential biological organometallic radical catalyst, has a formerly unanticipated, yet extensive, role in photoregulation in bacteria. The light-responsive cobalt-corrin AdoCbl performs this nonenzymatic role by facilitating the assembly of CarH photoreceptors into DNA-binding tetramers in the dark, suppressing gene expression. Conversely, exposure to light triggers the decomposition of this AdoCbl-bound complex by a still elusive photochemical mechanism, activating gene expression. Here, we have examined AdoRhbl, the non-natural rhodium analogue of AdoCbl, as a photostable isostructural surrogate for AdoCbl. We show that AdoRhbl closely emulates AdoCbl in its uptake by bacterial cells and structural functionality as a regulatory ligand for CarH tetramerization, DNA binding, and repressor activity. Remarkably, we find AdoRhbl is photostable even when bound "base-off/His-on" to CarH in vitro and in vivo. Thus, AdoRhbl, an antivitamin B 12 , also represents an unprecedented anti-photoregulatory ligand, opening a pathway to precisely target biomimetic inhibition of AdoCbl-based photoregulation, with new possibilities for selective antibacterial applications. Computational biomolecular analysis of AdoRhbl binding to CarH yields detailed structural insights into this complex, which suggest that the adenosyl group of photoexcited AdoCbl bound to CarH may specifically undergo a concerted non-radical syn-1,2-elimination mechanism, an aspect not previously considered for this photoreceptor., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Although the synthesis of mechanically interlocked molecules has been extensively researched, selectively constructing homogeneous linear [4]catenanes remains a formidable challenge. Here, we selectively constructed a homogeneous linear metalla[4]catenane in a one-step process through the coordination-driven self-assembly of a bidentate benzothiadiazole derivative ligand and a binuclear half-sandwich rhodium precursor. The formation of metalla[4]catenanes was facilitated by cooperative interactions between strong sandwich-type π-π stacking and non-classical hydrogen bonds between the components. Moreover, by modulating the aromatic substituents on the binuclear precursor, two homogeneous metalla[2]catenanes were obtained. The molecular structures of these metallacatenanes were unambiguously characterized by single-crystal X-ray diffraction analysis. Additionally, reversible structural transformation between metal-catenanes and the corresponding metallarectangles could be achieved by altering their concentration, as confirmed by mass spectrometry and NMR spectroscopy studies., (© 2024 Wiley‐VCH GmbH.)

Triphenylpnictogens EPh 3 (E=N, P, As, Sb, Bi) are able to displace the perfluorinated Cp* ligand in [Rh(COD)(C 5 (CF 3 ) 5 )] (COD=1,5-cyclooctadiene) in up to quantitative yield. The resulting ionic products contain [C 5 (CF 3 ) 5 ] - as uncoordinated counter anion. The cations feature [Rh(COD)] + fragments, coordinated by one (N, Bi), two (P, As) or three (Sb) triphenylpnictogen moieties. Whereas coordination via the pnictogen is observed for P, As and Sb, π-coordination of the aryl rings is observed for N and Bi., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

In this study, we examine the surface-derived electronic and chemical structures of nanostructured GaRh alloys as a model system for supported catalytically active liquid metal solutions (SCALMS), a novel catalyst candidate for dehydrogenation reactions that are important for the petrochemical and hydrogen energy industry. It is reported that under ambient conditions, SCALMS tends to form a gallium oxide shell, which can be removed by an activation treatment at elevated temperatures and hydrogen flow to enhance the catalytic reactivity. We prepared a 7 at. % Rh containing the GaRh sample and interrogated the evolution of the surface chemical and electronic structure by photoelectron spectroscopy (complemented by scanning electron microscopy) upon performing surface oxidation and (activation treatment mimicking) annealing treatments in ultrahigh vacuum conditions. The initially pronounced Rh 4d and Fermi level-derived states in the valence band spectra disappear upon oxidation (due to formation of a GaO x shell) but reemerge upon annealing, especially for temperatures of 600 °C and above, i.e., when the GaO x shell is efficiently being removed and the Ga matrix is expected to be liquid. At the same temperature, new spectroscopic features at both the high and low binding energy sides of the Rh 3d 5/2 spectra are observed, which we attribute to new GaRh species with depleted and enriched Rh contents, respectively. A liquefied and GaO x -free surface is also expected for GaRh SCALMS at reaction conditions, and thus the revealed high-temperature properties of the GaRh alloy provide insights about respective catalysts at work.

The masked transition-metal frustrated Lewis pairs [Cp*M(κ 3 N,N',N''-L)][SbF 6 ] (Cp*=η 5 -C 5 Me 5 ; M=Ir, 1, Rh, 2; HL=pyridinyl-amidine ligand) reversibly activate H 2 under mild conditions rendering the hydrido derivatives [Cp*MH(κ 2 N,N'-HL)][SbF 6 ] observed as a mixture of the E and Z isomers at the amidine C=N bond (M=Ir, 3Z, 3E; M=Rh, 4Z, 4E). DFT calculations indicate that the formation of the E isomers follows a Grotthuss type mechanism in the presence of water. A mixture of Rh(I) isomers of formula [(Cp*H)Rh(κ 2 N,N'-HL)][SbF 6 ] (5 a-d) is obtained by reductive elimination of Cp*H from 4. The formation of 5 a-d was elucidated by means of DFT calculations. Finally, when 2 reacts with D 2 , the Cp* and Cp*H ligands of the resulting rhodium complexes 4 and 5, respectively, are deuterated as a result of a reversible hydrogen abstraction from the Cp* ligand and D 2 activation at rhodium., (© 2024 Wiley‐VCH GmbH.)

The combination of achiral Cp*Rh(III) with chiral carboxylic acids (CCAs) represents an efficient catalytic system in transition metal-catalyzed enantioselective C-H activation. However, this hybrid catalysis is limited to redox-neutral C-H activation reactions and the adopt to oxidative enantioselective C-H activation remains elusive and pose a significant challenge. Herein, we describe the development of an electrochemical Cp*Rh(III)-catalyzed enantioselective C-H annulation of sulfoximines with alkynes enabled by chiral carboxylic acid (CCA) in an operationally friendly undivided cell at room temperature. A broad range of enantioenriched 1,2-benzothiazines are obtained in high yields with excellent enantioselectivities (up to 99 % yield and 98 : 2 er). The practicality of this method is demonstrated by scale-up reaction in a batch reactor with external circulation. A crucial chiral Cp*Rh(III) intermediate is isolated, characterized, and transformed, providing rational support for a Rh(III)/Rh(I) electrocatalytic cycle., (© 2024 Wiley‐VCH GmbH.)

The factors governing the acceleration of the oxidative addition of methyl iodide to pincer rhodium(I)-complexes induced by coronene have been computationally explored in detail using quantum chemical methods. Both the parent reaction and the coronene-mediated process proceed via a stepwise S N 2-type mechanism. It is found that the acceleration of the process derives from the formation of an initial supramolecular complex, mainly stabilized by electrostatic and π-π interactions, which significantly increases the electron richness of the complex. The impact of this effect on the reaction barrier has been quantitatively analyzed by applying the activation strain model in combination with the energy decomposition analysis method. In addition, the influence of other polycyclic aromatic hydrocarbons on the oxidative reaction has been also considered., (© 2024 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

Enantioselective C-H amination at a benzylic methylene is a vital disconnection towards chiral benzylamines. Here we disclose that butyric and valeric acid-derived tertiary amides can undergo highly enantioselective benzylic amination using an achiral anionic Rh complex that is ion-paired with a Cinchona alkaloid-derived chiral cation. A broad scope of compounds can be aminated encompassing numerous arene substitutions, amides, and two different chain lengths. Excellent tolerance of ortho substituents was observed, which has not been achieved before in asymmetric intermolecular C-H amination with Rh. We speculate that the tertiary amide group of the substrate engages in hydrogen bonding interactions directly with the chiral cation, enabling a high level of organisation at the transition state for C-H amination. This is in contrast with our previous work where a substrate bearing a hydrogen bond donor was required. Control experiments led to the discovery that methyl ethers also function as proficient directing groups under the optimised conditions, potentially also acting as hydrogen bond acceptors. This finding has the promise to dramatically expand the applicability of our ion-paired chiral catalysts., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Enantiomerically enriched crown ethers (CE) exhibit strong asymmetric induction in phase transfer catalysis, supramolecular catalysis and molecular recognition processes. Traditional methods have often been used to access these valuable compounds, which limit their diversity and consequently their applicability. Herein, a practical catalytic method is described for the gram scale synthesis of a class of chiral CEs (aza-crown ethers; ACEs) using Rh-catalyzed hydroamination of bis(allenes) with diamines. Using this approach, a wide range of chiral vinyl functionalized CEs with ring sizes ranging from 12 to 36 have been successfully prepared in high yields of up to 92 %, dr of up to >20 : 1 and er of up to >99 : 1. These vinyl substituted CEs allow for further diversification giving facile access to various CE derivatives as well as to their three-dimensional analogues using ring-closing metathesis. Some of these chiral CEs themselves display high potential for use in asymmetric catalysis., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Terpene-derived alkaloids show a variety of biological activities, including antioxidant, anti-inflammatory, antimicrobial and cytotoxicity effects. In this work, homologated monoterpene amines have been prepared via a rhodium-catalyzed hydroaminomethylation of biomass-based alkenes, such as (R)-limonene, linalool, myrcene and camphene, in combination with secondary amines of aliphatic and aromatic nature, namely morpholine and N-methylaniline, leading to highly chemo- and regioselective processes. The as-prepared amines were obtained in 50-99 % overall yields, and in vitro tested on a human colon cancer cell line (HCT-116) to evaluate their cytotoxic potential. The lead compound of the series (3 a) showed cytotoxicity in the micromolar range (IC50 52.46 μM) via the induction of cell death by apoptosis, paving the way towards further structure-activity relationship studies., (© 2024 The Authors. Chemistry & Biodiversity published by Wiley‐VHCA AG.)

A enantioselective tandem transformation, concerning asymmetric allylic decarboxylative addition and cyclization of N -nosylimines with vinylethylene carbonates (VECs), in the presence of [Rh(C 2 H 4 ) 2 Cl] 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.

Atropisomeric phosphines hold considerable significance in asymmetric catalysis, yet their synthesis presents a formidable challenge owing to intricate multistep procedures. In this context, a groundbreaking methodology has been presented for their preparation. This innovative approach entails an atroposelective rhodium-catalyzed C-H activation employing aryl and heteroaryl halides, chelated by a P(III) center. The essence of this strategy lies in its ability to directly construct chiral phosphine ligands in a single step, thereby exhibiting exceptional efficiency in terms of atom and redox economy. Illustrative examples serve to demonstrate the immense potential of in situ-formed ligands in asymmetric catalysis. Mechanistic experiments have further provided invaluable insights into this transformation., (© 2024 Wiley-VCH GmbH.)

Three-coordinated chlorogermylenes of the type [Ph 2 P(RN) 2 ]GeCl (3: R= t Bu; 4: R=Dip=2,6- i Pr 2 C 6 H 3 ), which bear an N,N-substituted iminophosphonamide ligand, were synthesized. The coordination behavior of 3 and 4 toward rhodium(I) complex was investigated. When 3 was treated with 1/2 of an equivalent of [RhCl(cod)] 2 (cod=1,5-cyclooctadiene), the corresponding chlorogermylene-Rh(I) complex 5 was obtained as orange crystals. In contrast, the reaction of 4 with a half equivalent of [RhCl(cod)] 2 under a CO atmosphere resulted in the formation of a five-membered germarhodacycle 7. Compounds 3, 4, 5, and 7 were characterized using NMR spectroscopies and single-crystal X-ray diffraction. Complex 5 can be employed as a catalyst for the hydrosilylation and hydroboration reactions of diphenylacetylene, thus demonstrating the utility of germylene ligands comparable to those of NHCs in the major transition metal catalytic processes., (© 2023 Wiley-VCH GmbH.)

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.

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 C 70 as a novel procedure for generating C 70 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 C 70 derivatives having a 12-membered ring opening., (Copyright © 2024, Castanyer et al.)

Herein, a highly efficient five-step reaction sequence to BODIPYs is presented. The key step is the combination of transition metal-catalyzed in-situ generation of aldehydes and their subsequent organocatalytic activation to yield dipyrromethanes, which are further converted to the corresponding BODIPY. Classic syntheses towards BODIPYs have relied on aldehydes or acid chlorides, which are often not commercially available and rather sensitive to handle. The presented approach starts from readily available and stable alkenes or aryl-bromides, which allows to extend the range of readily available BODIPYs that can be tailored for their specific use. The synthesis of 55 derivatives with overall yields of up to 78 % demonstrates the wide applicability and advantages of the presented method., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

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 k app 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., Competing Interests: 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., (© 2024 Published by Elsevier Ltd.)

Anionic cyclopentadienyl (Cp) and its pentamethyl-substituted derivative (Cp*) serve as crucial ligands for creating stable π-coordinated materials, including catalysts. From a structural perspective, the π-extended analog of Cp, known as an N-fused porphyrin (NFP), is recognized as an intriguing 18π aromatic chromophore, offering near-infrared (NIR) optical properties that can be fine-tuned through metal complexation. When coordinated with rhodium at the central NFP core, it forms a sandwich binuclear rhodium(III) complex along with terminal and bridging chloride ligands, denoted as Rh-1, and its bromo derivative, Rh-1-Br. In contrast to the bis-NFP complex of iron(II) reported previously by our team, both Rh-1 and Rh-1-Br complexes exhibit strong NIR optical properties and narrow HOMO-LUMO energy gaps, attributed to minimal orbital interactions between the two co-facial NFP ligands. Leveraging these NIR absorption properties, we assessed the photothermal conversion properties of Rh-1 and ligand 1, revealing high conversion efficiency. This suggests their potential application as photothermal agents for use in photothermal therapy., 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. Published by Elsevier Inc.)

In the title triazole-based N-heterocyclic carbene rhodium(I) cationic complex with a tetra-fluorido-borate counter-anion, [Rh(C 8 H 12 )(C 8 H 15 N 3 )(C 18 H 15 P)]BF 4 , 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 inter-actions 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., (© Lerch et al. 2024.)

Monocarbonyl rhodium complex LRh(CO), 1, which is stabilized by a pyrrole-based bis(phosphinimine) pincer ligand (L=κ 3 -NNN'=2,5-[ i Pr 2 P=N(4- i PrC 6 H 4 )] 2 -N'(C 4 H 2 ) - ), serves as a versatile platform for the dehydrogenation of group 14 substrates. Reaction with primary and secondary silanes and germanes (MesSiH 3 , Et 2 SiH 2 , Ph 2 GeH 2 , t BuGeH 3 ; Mes=mesityl) liberates H 2 and yields base-stabilized tetrylene compounds of the form κ 2 -L(CO)Rh(ER 2 ) (E=Si: R=Mes, H, 2; R=Et, 5; E=Ge: R=Ph, 6; R= t Bu, H, 8). The ":ER 2 " fragment in these species bridges between the rhodium center and a phosphinimine donor. Preliminary reactions between pinacol (Pin) and κ 2 -L(CO)Rh(ER 2 ), E=Si, Ge, indicate that such complexes can serve as silylene and germylene synthons, releasing :ER 2 and catalytically generating PinER 2 . In contrast, combination of complex 1 and MesGeH 3 does not yield the anticipated dehydrogenation product, but rather, transmetalation similar to that observed upon reaction between 1 and 3,5-dimethylphenylborane prevails., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

A new generation of soluble phenothiazinyl merocyanine substituted polyacetylenes can be readily synthesized by rhodium-catalyzed polymerization of the corresponding 3-ethynyl phenothiazines, accessible by Sonogashira coupling and Knoevenagel condensation. UV/Vis and fluorescence spectroscopy of 7-acceptor-substituted phenothiazinyl polyacetylenes reveal that these polyacetylenes with conjugatively ligated merocyanines are luminescent in solution with positive emission solvatochromism and, in some cases, with distinct solid-state luminescence., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

We extend the highly-parallelizable open-source electronic transport code TRANSEC (Feldman et al 2014 Phys. Rev. B 90 035445;https://gitlab.com/computational-physics2/transec/) to perform real-space atomic-scale electronic transport calculations with periodic boundary conditions in the lateral dimensions. We demonstrate the use of TRANSEC in periodic Cu and Rh bulk structures and in large periodic Rh point contacts, in preparation to perform calculations of reflection probability across Rh grain boundaries., (© 2024 IOP Publishing Ltd.)

Reaction of the tris-hypersilyl nonagermanide Zintl cluster salt, K[Ge 9 (Hyp) 3 ] (Hyp=Si(SiMe 3 ) 3 ) with [Rh(η 2 ,η 2 -L)Cl] 2 (L=1,5-cyclooctadiene, COD; norbornadiene, NBD) afforded eleven- and twelve-vertex homo-multimetallic clusters by cluster core expansion. Using a stepwise procedure, starting from the Zintl cluster [Rh(COD){Ge 9 (Hyp) 3 }] and [Ir(COD)Cl] 2 , this methodology was expanded for the synthesis of eleven-vertex hetero-multimetallic clusters. A mechanism for the formation of these first examples of closo eleven-vertex Zintl clusters is proposed, informed by density functional theory calculations., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Axially chiral open-chained olefins are an underexplored class of atropisomers, whose enantioselective synthesis represents a daunting challenge due to their relatively low racemization barrier. We herein report rhodium(I)-catalyzed hydroarylative cyclization of 1,6-diynes with three distinct classes of arenes, enabling highly enantioselective synthesis of a broad range of axially chiral 1,3-dienes that are conformationally labile (ΔG ≠ (rac)=26.6-28.0 kcal/mol). The coupling reactions in each category proceeded with excellent enantioselectivity, regioselectivity, and Z/E selectivity under mild reaction conditions. Computational studies of the coupling of quinoline N-oxide system reveal that the reaction proceeds via initial oxidative cyclization of the 1,6-diyne to give a rhodacyclic intermediate, followed by σ-bond metathesis between the arene C-H bond and the Rh-C(vinyl) bond, with subsequent C-C reductive elimination being enantio-determining and turnover-limiting. The DFT-established mechanism is consistent with the experimental studies. The coupled products of quinoline N-oxides undergo facile visible light-induced intramolecular oxygen-atom transfer, affording chiral epoxides with complete axial-to-central chirality transfer., (© 2023 Wiley-VCH GmbH.)

Generating reliable data on functional group compatibility and chemoselectivity is essential for evaluating the practicality of chemical reactions and predicting retrosynthetic routes. In this context, we performed systematic studies using a functional group evaluation kit including 26 kinds of additives to assess the functional group tolerance of carbene-mediated reactions. Our findings revealed that some intermolecular heteroatom-hydrogen insertion reactions proceed faster than intramolecular cyclopropanation reactions. Lewis basic functionalities inhibited rhodium-catalyzed C-H functionalization of indoles. While performing these studies, we observed an unexpected C-H functionalization of a 1-naphthol variant used as an additive.

The exogenous administration of nitric oxide (NO) is considered a potential therapeutic treatment against a great variety of diseases due to its significant role in multiple physiological functions. Due to the gaseous nature, short lifetime and dose- and tissue-dependent activity of this molecule, the development of new administration procedures is required to control the NO delivery in terms of dosage, timing, and location. In this work, we propose a new molecular material based on robust metal-organic polyhedra (MOPs) for controlled NO release. We select dirhodium paddlewheel complex-based cuboctahedral MOPs (RhMOP), in which NO can chemically coordinate to the open-metal sites at the axial sites of dirhodium paddlewheel moieties. We further prepare amorphous coordination polymer particles (CPPs) by connecting RhMOP with bis(imidazole) linkers at the external axial sites. Both molecular MOPs and polymeric CPPs show relevant NO payloads and the release of NO can be triggered by two different stimuli: light and humidity. We show that imidazole ligands coordinating to the external axial sites of the paddlewheel moieties tune the light-triggered NO release property. We further demonstrate that the size and the extrinsic pores of CPPs are important for enhanced NO release.

The exponential proliferation of conformers makes it impossible to examine the entire population in most systems. Controlling conformational ensembles is thus pivotal in many areas of chemistry. Rh 2 (esp) 2 , a dicarboxylate-derived paddlewheel rhodium complex, is one of the most effective catalysts for nitrene chemistry. Its enormous success has led to preparing many analogous complexes. However, there has been little consideration for the conformational dynamics of the parent catalyst. Herein, we report a new ligand modification principle that prevents conformer interconversion. The resulting complex comprises two isolable conformers, whose structures have been determined by X-ray diffraction. Combined experimental and computational data has revealed similarities and dissimilarities between the conformationally confined and parent complexes. Three model cases have demonstrated the utility of conformational fixation in the development of stereoselective catalysts for nitrene transfer reactions. The design principle described in this study can be combined with other established modification strategies, serving as a springboard for further advancement of the chemistry of paddlewheel metal complexes., (© 2023 Wiley-VCH GmbH.)