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This report presents a selective synthetic approach towards borazine from ammonia borane using a dinuclear rhodium olefin homogeneous catalyst. The synthesis and spectroscopic characterization of a dirhodium ammonia borane complex as an intermediate provides insight into a possible mode of activation. [ABSTRACT FROM AUTHOR]

Thiophene, a heterocyclic compound characterized by a five-membered ring comprising four carbon atoms and one sulfur atom, has garnered significant attention in recent research due to its versatile applications in medicinal and chemosensing fields. Thiophene derivatives formed complexes with various transition metals. These complexes exhibit promising anti-inflammatory, anticancer, antibacterial, antifungal and other biological properties. Certainly, the complexation phenomenon involving thiophene derivatives can be effectively used for the recognition of various cations. Thiophene-based compounds can act as selective ligands, forming stable complexes with specific heavy metal ions. This property has significant implications for environmental monitoring, industrial safety, and public health, as the presence of heavy metal ions beyond permissible levels can lead to detrimental effects. This paper explored the versatile applications of thiophene derivatives, investigating their chemosensing potential for the determination of various metal ions covering the period from 2018 to 2024. Thiophene derivatives serve as versatile ligands for metal ions and exhibit fluorescence and colorimetric changes for selective detection of metal ions. Additionally, this study also explores the anticancer efficacy demonstrated by metal complexes derived from thiophene, with a specific emphasis on those formed with platinum-group metals (Ir(III), Ru(II), Ru(III), Rh, Os(II), Os(IV), Pd(II), Pt(II)). [ABSTRACT FROM AUTHOR]

The κ2‐(P,N)−phosphine ligand precursor NH(CH2CH2PCy2)2 can be used for the synthesis of the rhodium(I) complex [Rh(CO){ĸ3‐(P,N,P)−Cy2PC2H4NHC2H4PCy2}][Cl] (1). The deprotonated complex [Rh(CO){ĸ3‐(P,N,P)−Cy2PC2H4NC2H4PCy2}] (2) shows a cooperative reactivity of the PNP ligand in the activation reaction of SO2F2 to yield the rhodium fluorido complex trans‐[Rh(F)(CO){ĸ2‐(P,P)−Cy2PC2H4N(SO2F)C2H4PCy2}]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−CF3 and different fluorine sources such as SF4 or Selectfluor®. However, the treatment of complex 3 with XeF2 in the presence of CsF resulted in the formation of the unique fluorido rhodium(III) complex cis,trans‐[Rh(F)3(CO){ĸ2‐(P,P)−Cy2PC2H4N(SO2F)C2H4PCy2}]2 (4). In the presence of pyridine(HF)X or BF3 the fluorido complex 3 converted into the dicationic complexes [Rh(CO){ĸ2‐(P,P)−Cy2PC2H4N(SO2F)C2H4PCy2}]2[XF]2, X=HF (5) or BF3 (6), respectively. [ABSTRACT FROM AUTHOR]

L3‐edge high‐energy‐resolution fluorescence‐detection X‐ray absorption near‐edge structure (XANES) spectra for palladium and rhodium compounds are presented, with focus on their electronic structures. The data are compared with transmission XANES spectra recorded at the K‐edge. A correlation between the absorption edge energy and the metal ion oxidation state is not observed. Despite the different filling of the 4d orbitals and different local coordination, the Rh and Pd compounds show remarkably similar spectral shapes. Calculation of the density of states and of the L3‐XANES data reproduce the experimental results. [ABSTRACT FROM AUTHOR]

The building of N-heterocyclic cores endures an influential area of research due to their ubiquitous presence in natural products, agrochemicals, and small bioactive molecules. Over the past two decades, the synthesis of N-heterocycles via C-H activation comes out as a dominating synthetic protocol in atom-economic manner. The creation of C-C/C-N bonds acts as a key determining step for the building of nitrogen-based heterocycles via direct C-H activation protocol, which could serve as a fascinating concept. In recent years, Group 9 (Co, Rh & Ir) transition metal emerged as a robust catalytic system for the development of valuable N-heterocyclic scaffolds among other transition metals due to their mild reaction conditions, high reactivity, and functional group tolerance. A diverse type of arenes such as anilines/anilides, benzamides, hydrazones, ketoximes, benzylamine, and N-aryl nitrones were subjected to the C-H bond activation for the annulation reaction. Moreover, unsaturated compounds such as alkyne and olefin as coupling partners are again the most used companions for the same purpose, i.e., formation of N-heterocycles. Therefore, this review centers on the up-to-date reports on N-heterocycles synthesis by implementing alkynes and olefins as coupling partners through Group 9 transition metals' catalysis. The methodologies will be based on the coupling of alkynes and olefin, which preferably react in an intermolecular fashion. The scope, limitation, and mechanistic investigation of the Group 9 metal-activated C-H functionalization for the access of N-containing heterocycles with unsaturated reacting partners are the primary focus of the current review. [ABSTRACT FROM AUTHOR]

This article, published in the journal Synlett, discusses a study on the development of a rhodium-catalyzed direct vinylene annulation reaction. The researchers focused on using vinyl selenones as vinylene-transfer reagents and successfully demonstrated a three-component reaction to construct isoquinolone scaffolds. The article includes a table showing the optimization of reaction conditions. The study also explored the scope and limitations of the reaction system, proposing a mechanism for the coupling reaction and concluding that further optimization is needed. [Extracted from the article]

Previous studies on bimetallic paddlewheel compounds have established a direct correlation between metal–metal distance and ligand torsion angles, leading to the rule that higher torsion results in longer metal‐metal bond distances. Here, the new discovery based on diarylformamidinate Ru₂⁵⁺ paddlewheel compounds [Ru2Cl(DArF)4] that show an opposite behavior is reported: higher torsions lead to shorter metal–metal distances. This discovery challenges the assumption that internal rotation solely impacts the δ bond. By combining experimental and theoretical techniques, it is demostrated that this trend is associated with previously overlooked π metal‐ligand interactions. These π metal‐ligand interactions are a direct consequence of the paddlewheel structure and the conjugated nature of the bidentate ligands. This findings offer far‐reaching insights into the influence of equatorial ligands and their π‐conjugation characteristics on the electronic properties of paddlewheel complexes. That this effect is not exclusive of diruthenium compounds but also occurs in other bimetallic cores such as ditungsten or dirhodium is demonstrated, and with other ligands showing allyl type conjugation. These results provide a novel approach for fine‐tuning the properties of these compounds with significant implications for materials design. [ABSTRACT FROM AUTHOR]

The titanium dioxide (TiO2) semiconductor's wide band gap property restricts its application in a variety of fields. To ensure cost-effectiveness and time efficiency, researchers emphasized material modeling and theoretical analysis. This study employs a Density Functional Theory approach to investigate how the presence of transition metal elements (TME) like rhodium (Rh) and rhenium (Re) affects the optoelectronic properties of TiO2. The study was carried out using the VASP software package and the plane-wave pseudopotential technique. The formation energy, electronic band structure, and optical properties of TiO2 were affected by the addition of both Rh and Re as doping materials. The outcomes of the band structure and total density of states (TDOS), point out notable alterations in the energy gap (Eg) of TiO2. The plot of the band structure illustrates that the introduction of Re leads to a more substantial reduction in the TiO2 band gap compared to Rh. The introduction of numerous sub-states into the band gap causes the valence band to approach the conduction band at the Gamma point. The band gap reduction caused by the addition of Rh and Re TME is confirmed by the relocation of the TDOS to lower energies in the doped TiO2 structure. Furthermore, significant changes in the partial density of states of TiO2 upon Re doping have been observed at the bottom of the conduction band, highlighting the effectiveness of Re doping in modifying the electronic band structure of TiO2. The outcomes of band structure and TDOS proved that TME with high atomic mass is certain to decrease TiO2's band gap to the range required for usage as a photocatalytic material. Rh and Re doping in TiO2 alter their optical properties, making them suitable for optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this study, a Rh(III)-catalyzed C–H/N–H [4+2] annulation of oxadiazolones with iodonium ylides has been developed, which afforded a series of diverse fused-isoquinolines and fused-pyridines in moderate to high yields. These divergent synthesis protocols featured mild conditions, broad substrate scope, and functional-group compatibility. In addition, scale-up synthesis, related applications and preliminary mechanistic explorations were also accomplished. [ABSTRACT FROM AUTHOR]

Cycloaddition reactions play a pivotal role in synthetic chemistry for the direct assembly of cyclic architectures. However, hurdles remain for extending the C4 synthon to construct diverse heterocycles via programmable [4+n]-cycloaddition. Here we report an atom-economic and modular intermolecular cycloaddition using furan-fused cyclobutanones (FCBs) as a versatile C4 synthon. In contrast to the well-documented cycloaddition of benzocyclobutenones, this is a complementary version using FCB as a C4 reagent. It involves a C-C bond activation and cycloaddition sequence, including a Rh-catalyzed enantioselective [4 + 2]-cycloaddition with imines and an Au-catalyzed diastereoselective [4 + 4]-cycloaddition with anthranils. The obtained furan-fused lactams, which are pivotal motifs that present in many natural products, bioactive molecules, and materials, are inaccessible or difficult to prepare by other methods. Preliminary antitumor activity study indicates that 6e and 6 f exhibit high anticancer potency against colon cancer cells (HCT-116, IC50 = 0.50 ± 0.05 μM) and esophageal squamous cell carcinoma cells (KYSE-520, IC50 = 0.89 ± 0.13 μM), respectively. Cycloaddition reactions play a pivotal role in synthetic chemistry for the direct assembly of cyclic architectures. However, hurdles remain for extending the C4 synthon to construct diverse heterocycles via programmable [4+n]-cycloaddition. Herein, the authors report an intermolecular cycloaddition using furan-fused cyclobutanones as a C4 synthon. [ABSTRACT FROM AUTHOR]

Described herein is a dirhodium(II)‐catalyzed silylation of propargyl esters with hydrosilanes, using tertiary amines as axial ligands. By adopting this strategy, a range of versatile and useful allenylsilanes can be achieved with good yields. This reaction not only represents a SN2′‐type silylation of the propargyl derivatives bearing a terminal alkyne moiety to synthesize allenylsilanes from simple hydrosilanes, but also represents a new application of dirhodium(II) complexes in catalytic transformation of carbon‐carbon triple bond. The highly functionalized allenylsilanes that are produced can be transformed into a series of synthetically useful organic molecules. In this reaction, an intriguing ON‐OFF effect of the amine ligand was observed. The reaction almost did not occur (OFF) without addition of Lewis base amine ligand. However, the reaction took place smoothly (ON) after addition of only catalytic amount of amine ligand. Detailed mechanistic studies and density functional theory (DFT) calculations indicate that the reactivity can be delicately improved by the use of tertiary amine. The fine‐tuning effect of the tertiary amine is crucial in the formation of the Rh−Si species via a concerted metalation deprotonation (CMD) mechanism and facilitating β‐oxygen elimination. [ABSTRACT FROM AUTHOR]

The interfacial structure between Rh and the metal oxide support (or promoter) is thought to play an essential role in the synthesis of C2-oxygenated compounds such as acetic acid (CH3COOH). However, due to the complexity of the interface structure, the CH3COOH synthesis pathway has yet to be explored theoretically at the metal/metal oxide interface. In this study, we examined the CH3COOH synthesis pathway at the Rh surface and Rh/metal oxide interface based on the systematic investigation of bond disconnection of the CH3COOH molecule. First, CH3COOH synthesis pathways that include small activation energy Ea(c) were explored on the Rh(111) and it was shown that the reaction pathways CH + CO(H) → CHCO(H) → CH2CO(H) → CH3COH → CH3COOH were found [the rate-limiting step (RLS) is the C=O bond connection with Ea(c) = 1.41 eV]. After that, the CH3COOH synthesis pathway at the Rh/ZrO2 interface was investigated, and it was found that the CH3COOH synthesis pathway via the acetyl (CH3CO) generated from Rh–CH3 and Rh–CO with an oxygen atom in Rh–CO interacted with Zr cation (the RLS was the C–C bond connection with Ea(c) = 0.73 eV). This study provides guidelines for the design of a rational active metal/metal oxide interface for C2 oxygenates synthesis. [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]

Stabilization of hexaphyrin(1.0.1.0.1.0) (named "rosarin") in its 25π radical state is achieved using a hetero‐bimetal‐coordination strategy. The antiaromatic BF2 complex B‐1 was first synthesized, and then rhodium ion was inserted into B‐1 to produce the BF2/Rh(CO)2 mixed complex Rh‐B‐1 as a highly air‐stable radical. The structures of B‐1 and Rh‐B‐1 were determined by single‐crystal X‐ray diffractions, and the antiaromatic or radical character was identified by various spectroscopy evidence and theoretical calculations. Rh‐B‐1 exhibits excellent redox properties, enabling amphoteric aromatic‐antiaromatic conversion to their 24/26π states. Compared to the 24/26π conjugation systems on the same skeleton, Rh‐B‐1 has the narrowest electrochemical and optical band gaps, with the longest absorption band at 1010 nm. The ring‐current analysis reveals intense paratropic currents for B‐1 and co‐existing diatropic‐paratropic currents for Rh‐B‐1. This hetero‐bimetal‐coordination system provides a novel platform for organic radical stabilization on porphyrinoids, showing the prospect of modulating ligand oxidation states through rational coordination design. [ABSTRACT FROM AUTHOR]

The use of gem‐difluorinated cyclopropanes (gem‐DFCPs) as fluoroallyl surrogates under transition‐metal catalysis has drawn considerable attention recently but such reactions are restricted to producing achiral or racemic mono‐fluoroalkenes. Herein, we report the first enantioselective allylation of indoles under rhodium catalysis with gem‐DFCPs. This reaction shows exceptional branched regioselectivity towards rhodium catalysis with gem‐DFCPs, which provides an efficient route to enantioenriched fluoroallylated indoles with wide substrate scope and good functional group tolerance. [ABSTRACT FROM AUTHOR]

The impact of isomerism of pyrimidine-based ligands and their rhodium(III) complexes with regard to their structures and properties was investigated. Two isomeric ligands, 4-(3,5-dimethyl-1H-pyrazol-1-yl)-2,5-diphenylpyrimidine (HL2,5) and 4-(3,5-dimethyl-1H-pyrazol-1-yl)-2,6-diphenylpyrimidine (HL2,6), were synthesized. The ligands differ by the degree of steric bulk: the molecular structure of HL2,5 is more distorted due to presence of pyrazolyl and phenyl groups in the neighbouring positions 4 and 5 of the pyrimidine ring. The complexation of HL2,5 and HL2,6 with RhCl3 leads to the sp2 C–H bond activation, resulting in the isolation of two complexes, [RhL2,5(Solv)Cl2]·nEtOH and [RhL2,6(Solv)Cl2]·nEtOH (Solv = H2O, EtOH), with the deprotonated forms of the pyrazolylpyrimidine molecules which coordinate the Rh3+ ion as N^N^C-tridentate ligands. According to DFT modelling, the mechanism of the deprotonation involves (i) the C–H bond breaking in the 2-phenyl group followed by the coordination of the C atom to the Rh atom, (ii) the protonation of coordinated chlorido ligand, (iii) the ejection of the HCl molecule and (iv) the coordination of the H2O molecule. The ligand isomerism has an impact on emission properties and cytotoxicity of the complexes. Although the excited states of the complexes effectively deactivate through S0/T1 and S0/S1 crossings associated with the cleavage of the weak H2O ligands upon excitation, the [RhL2,5(Solv)Cl2]·nEtOH complex appeared to be emissive in the solid state, while [RhL2,6(Solv)Cl2]·nEtOH is non-emissive at all. The complexes show significant cytotoxic activity against cancerous HepG2 and Hep2 cell lines, with the [RhL2,6(Solv)Cl2]·nEtOH complex being more active than its isomer [RhL2,5(Solv)Cl2]·nEtOH. On the other hand, noticeable cytotoxicity of the latter against HepG2 is supplemented by its non-toxicity against non-cancerous MRC-5 cells. [ABSTRACT FROM AUTHOR]

The dehydrogenation of dimethylamine-borane (DMAB) catalyzed by the iminophosphonamide rhodium(III) complexes [Cp*RhCl{Ph2P(N–p-Tol)(NR)}] (Iа, R = p-Tol; Ib, R = Me) as well as their in situ formed fulvene [(η4-C5Me4CH2)Rh(NPN)] (IIa, IIb) and diene [(η4-C5Me5H)Rh(NPN)] (IIIa, IIIb) rhodium(I) derivatives is studied. Catalysts IIIa and IIIb turn out to be the most active and demonstrate a TOF activity of 110 (IIIа) and 540 h–1 (IIIb) at 40°С in toluene. The activity decreases significantly in more polar and coordinating THF. At the same time, the rate of DMAB dehydrogenation by complexes Iа and Ib is lower by 10–30 times, and fulvene complexes Iа and Ib are rapidly deactivated after the active initial period (<20% conversion). The kinetic studies show that the reaction has the first order with respect to the substrate and the catalyst. The model 11В NMR experiments confirm that the reaction proceeds via the intermediate formation of a monomer Me2N=BH2, which rapidly dimerizes to (Me2N–BH2)2. The mechanism of DMAB dehydrogenation with the formation of unstable hydride intermediate [Cp*RhH{Ph2P(N–p-Tol)(NR)}] (IVa, IVb) is proposed on the basis of the preliminarily 31Р NMR results and published data. [ABSTRACT FROM AUTHOR]

To date, it remains challenging to achieve a general and catalytic α‐arylation of cyclic 1,3‐dicarbonyls, particularly ubiquitous heteroaromatic ones. In most cases, the preparation of their medically significant arylated derivatives requires multistep synthetic sequences. Herein, we introduce a new, convenient strategy involving the conversion of cyclic 1,3‐dicarbonyls to cyclic iodonium ylides (CIYs), followed by rhodium‐catalyzed α‐arylation with arylboronic reagents via carbene coupling. This approach is mild, operationally simple, base‐free, biocompatible, and exhibits broad substrate scope (>100 examples), especially with respect to various heteroaromatic 1,3‐dicarbonyls and ortho‐substituted or base‐sensitive arylboronic acids. Importantly, owing to the excellent compatibility with various arylboronic acids or boronate esters (ArBpin, ArBneop, or ArBF3K), this method allows the late‐stage installation of heterocyclic 1,3‐dicarbonyl motifs in highly complex settings. The utility of this transformation is further demonstrated through significantly simplifying the synthesis of several bioactive molecules and natural products. [ABSTRACT FROM AUTHOR]

The catalytic activity of cyclobutadiene rhodium complexes was investigated in various transformations of alkynes. Complexes [Rh(C4Et4)Hal]n (at 1 mol% loading) were found to promote hydrosilylation of 1-octyne selectively giving 1-Z-, 1-E-, or 2-Et3Si-1-octene depending on the nature of the halide ligand and the presence of additional ligand PPh3. Complex [Rh(C4Et4)(p-xylene)]+ (1 mol%) also efficiently catalyzed the polymerization of phenylacetylene. At the same time, we found that various cyclobutadiene rhodium complexes do not catalyze the Diels–Alder reaction, alkyne hydration, and 1,4-addition of boronic acids to cyclohexanone. New complexes [Rh(C4Et4)(PPh3)2]BF4 and [Rh(C4Et4)(C10H8)]PF6 were also synthesized and their structures were established by X-ray diffraction. [ABSTRACT FROM AUTHOR]

This article discusses the development of a catalytic method for the magnesiation of alkyl fluorides using magnesium powder. Alkylmagnesium reagents, such as Grignard reagents, are important tools in organic synthesis, but the preparation of alkylmagnesium reagents from alkyl fluorides has been challenging due to the high bond-dissociation energy of C-F bonds. The researchers used a bimetallic rhodium-aluminum complex as a catalyst to activate the C-F bond and successfully magnesiate alkyl fluorides, including secondary and tertiary ones. The method offers a new approach for the synthesis of alkylmagnesium reagents and expands the range of available starting materials. [Extracted from the article]

Utilizing rhodium complexes to catalyze 2‐vinylbenzaldehyde derivatives has proven to be a valuable strategy in constructing indanone moieties. In this study, the stoichiometric reactions of Wilkinson's catalyst RhCl(PPh3)3 with 2‐vinylbenzaldehyde derivatives were investigated, leading to the formation of rhodaindanone complexes (2). Notably, the transformation of of rhoda‐1‐indanone (2 a) to rhoda‐2‐indanone (3) was achieved for the first time. In comparision, the reactivity of IrCl(PPh3)3 and Ir(CO)(CH3CN)(PPh3)2 ⋅ BF4 towards 2‐vinylbenzaldehyde derivatives affords irida‐2‐indanone complexes (4) and fused iridacycles (5), respectively. These newly prepared coumpounds represent the first metellacycles resulting from the reactions between 2‐vinylbenzaldehyde derivatives and rhodium/iridium complexes and may provide further insights into the catalytic processes involving 2‐vinylbenzaldehyde derivatives for synthesizing indanone compounds. [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 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. [ABSTRACT FROM AUTHOR]

The combination of different donor moieties often results in unconventional coordination behavior. This contribution describes the synthesis of a new hybrid ligand, phosphanylferrocene amidine Ph2PfcN=CHNMe2 (1; fc=ferrocene‐1,1′‐diyl), and its coordination behavior toward the light platinum metals. Reacting compound 1 with [PdCl2(MeCN)2] produced the chelate complex [PdCl2(1‐κ2P,N)] and the bis (phosphane) complex trans‐[PdCl2(1‐κP)2], depending on the ligand‐to‐metal stoichiometry. Halide removal from [PdCl2(1‐κ2P,N)] with Na[BARF] afforded the chloride‐bridged dimer [Pd2(μ‐Cl)2(1‐κ2P,N)2][BARF]2, which was presumably in equilibrium with the mononuclear κ3‐complex [PdCl(1‐κ3Fe,P,N)][BARF] in solution (BARF=tetrakis [3,5‐bis(trifluoromethyl)phenyl]borate). The reactions of 1 with the isoelectronic precursors [(arene)MCl(μ‐Cl)]2 (M/arene=Ru(II)/p‐cymene, and Rh(III)/C5Me5) generated the respective bridge‐cleavage products [(arene)MCl2(1‐κP)], which transformed into the P,N‐chelate complexes [(arene)MCl(1‐κ2P,N)][BARF] when treated with Na[BARF] as a chloride scavenger. All this suggests preferential coordination the phosphane moiety to soft metal ions, while the coordination of the amidine moiety can be induced through changing the reaction stoichiometry or by generating a vacant coordination site at the metal ion. The compounds were characterized using a combination of standard spectroscopic methods (multinuclear NMR, IR, and ESI MS) and single‐crystal X‐ray crystallography, and compounds 1 and 3 were further studied by cyclic voltammetry. [ABSTRACT FROM AUTHOR]

Monocarbonyl rhodium complex LRh(CO), 1, which is stabilized by a pyrrole‐based bis(phosphinimine) pincer ligand (L=κ3‐NNN'=2,5‐[iPr2P=N(4‐iPrC6H4)]2‐N'(C4H2)−), serves as a versatile platform for the dehydrogenation of group 14 substrates. Reaction with primary and secondary silanes and germanes (MesSiH3, Et2SiH2, Ph2GeH2, tBuGeH3; Mes=mesityl) liberates H2 and yields base‐stabilized tetrylene compounds of the form κ2‐L(CO)Rh(ER2) (E=Si: R=Mes, H, 2; R=Et, 5; E=Ge: R=Ph, 6; R=tBu, H, 8). The ":ER2" fragment in these species bridges between the rhodium center and a phosphinimine donor. Preliminary reactions between pinacol (Pin) and κ2‐L(CO)Rh(ER2), E=Si, Ge, indicate that such complexes can serve as silylene and germylene synthons, releasing :ER2 and catalytically generating PinER2. In contrast, combination of complex 1 and MesGeH3 does not yield the anticipated dehydrogenation product, but rather, transmetalation similar to that observed upon reaction between 1 and 3,5‐dimethylphenylborane prevails. [ABSTRACT FROM AUTHOR]

A family of transition metal complexes of meso‐aryl‐2‐aza‐21‐carbaporphyrin (N‐confused porphyrin, NCP) derivatives acting as ortho‐metallating ligands for ruthenium(II), rhodium(III), and iridium(III) is synthesized and characterized by XRD, spectroscopic, and electrochemical methods. The chirality of these systems is shown by the separation of the enantiomers and analyzed by circular dichroism and DFT. A preliminary catalytic study indicates the activity of the iridium(III) ortho‐metallated complexes in the N‐heterocyclization of primary amines with diols. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of three compounds [Rh(η5‐C5Me5)Cl(N^N)]PF6 (N^N=4,4'‐disubstituted‐2,2'‐bipyridines, 1–3) are described. The cationic complexes contain the bidentate ligands N^N=4,4'‐di‐tert‐butyl‐2,2'‐bipyridine (1), N^N=4,4'‐dinonyl‐2,2'‐bipyridine (2) and N^N=4,4'‐diamino‐2,2'‐bipyridine (3). The complex salts were obtained by the bridge‐splitting reaction from the precursor [{Rh(η5‐C5Me5)(μ‐Cl)Cl}2] and subsequent salt metathesis affording their corresponding hexafluorido phosphate salts. All compounds were characterized by elemental analysis and spectroscopic means. Additionally, the molecular structure of compound 3 in the solid was determined by a single‐crystal X‐ray diffraction study. The cytotoxicity of all three compounds was examined by MTT assay against two cancer cell lines – HT‐29 (colon adenocarcinoma) and MCF‐7 (human breast adenocarcinoma) ‐ and normal human fibroblast cells (GM5657T). Compound 1 has moderate cytotoxicity against both cell lines, while compound 2 is seven to nine times more cytotoxic than cisplatin against MCF‐7 and HT‐29, respectively. In contrast to cisplatin, both compounds are more active against cancer cells than fibroblasts, thus showing some cancer selectivity. [ABSTRACT FROM AUTHOR]

This article discusses the synthesis of isocoumarins using Rhodium (Rh) complexes as catalysts. The authors explore the use of phenacyl phosphoniums and iodonium ylides as building blocks in this process. They present their experimental findings, optimization of reaction conditions, and the scope of the reaction with various phenacyl phosphoniums. The research provides valuable insights into the synthesis of isocoumarins using Rh-catalyzed C-H activation. Additionally, the document provides detailed information on the synthesis and characterization of specific compounds, including their chemical structures, yields, physical properties, and spectroscopic data. [Extracted from the article]

The selective reduction of terminal alkynes to alkenes was investigated using common cationic diphosphane rhodium complexes of the type [Rh(PP)(diolefin)]X (PP=diphosphane, X=anion). The effectiveness of the catalyst was demonstrated in the semi‐hydrogenation of dehydroisophytol (DIP), an industrial produced intermediate of vitamin E. The present study highlights the high activity and good selectivity of this simple catalytic system. However, deactivation increases at higher DIP concentrations. Several strategies to circumvent the deactivation are presented. [ABSTRACT FROM AUTHOR]

The Rh(I)‐catalyzed denitrogenative annulation reactions of 1,2,3‐thiadiazoles are a new direct approach to synthesizing densely functionalized heterocycles. The synthesis of multisubstituted thiophenes is possible using this methodology, however the difficulty to predict which regioisomer will form is a current limitation. In this current work, systematic computational and experimental studies were performed addressing how the terminal alkyne substituent effects regioselectivity. The data revealed that the electronic and steric properties of the alkyne substituent effects regioselectivity, including whether the group is aryl or alkyl. The insight gained from this study has allowed the development of a framework for predicting regioselectivity for the Rh(I)‐catalyzed denitrogenative transannulation of 1,2,3‐thiadiazoles with terminal alkynes. [ABSTRACT FROM AUTHOR]

The rhodium complex [(C5H2tBu2CH2tBu)RhCl2]2 with an asymmetric cyclopentadienyl ligand was prepared in 95% yield by the reaction of [(cod)RhCl]2 with tert-butylacetylene in the presence of AlCl3. A similar reaction in the presence of InBr3 gave the cationic fulvene complex [(C5H2tBu2 = CHtBu)Rh(cod)]InBr4 (70%), which can add alcohols ROH and produce more bulky catalysts [(C5H2tBu2CH(OR)tBu)RhCl2]2. The enantiomers of these planar-chiral complexes were separated by thin-layer chromatography in the presence of L-phenylglycinol. The complexes catalyze the reactions of arylhydroxamates with alkenes giving dihydroisoquinolones in excellent yields (80–90%), but with moderate enantioselectivity (typically 20–50% ee). [ABSTRACT FROM AUTHOR]

Samples of model single-site catalysts based on iridium and rhodium were synthesized by immobilizing the complexes [Ir(COD)(IMes)Cl] and [Rh(COD)(IMes)Cl] (where COD is 1,5-cyclooctadiene and IMes is 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) on silica, the surface of which was modified with a linker containing a diphenylphosphine group (Ph2P). The supports were silicon plates with a flat surface coated with a layer of natural oxide 1–3 nm thick (Si–SiO2(nat)) or with a specially grown SiO2 film (∼300 nm) (Si–SiO2(ox)). The states of chemical elements in the modified silicon plates and samples of model catalysts were determined by XPS. Based on the results obtained, the nature of the coordination of the immobilized complexes was assumed. Samples of the catalysts were tested in the reaction of gas-phase hydrogenation of propene with parahydrogen. [ABSTRACT FROM AUTHOR]

Coordination of a pyridine‐pyrazole‐based PNN(H) ligand to RhI produces a family of neutral (1) and cationic (2Cl) RhI complexes. Deprotonation of the parent Rh chloride complex with LiNiPr2 results in formation of a dinuclear LiCl bridged species 3 bearing a pyrazolate fragment. Complexes 1, 2Cl and 3 were tested as precatalyst for the dehydrocoupling of amine boranes. All complexes studied show activity for the formation of cyclic oligomers with N‐methylcyclotriborazane as the main product. Base activation of the neutral Rh chloride complex 1 produces catalyst systems that are significantly more active than the parent system, suggesting that dehydrohalogenation of the Rh chloride precatalyst 1 is one of the key steps for catalyst formation. [ABSTRACT FROM AUTHOR]

Millions of tons of acetyl derivatives such as acetic acid and acetic anhydride are produced each year. These building blocks of chemical industry are elaborated into esters, amides, and eventually polymer materials, pharmaceuticals, and other consumer products. Most acetyls are produced industrially using homogeneous precious metal catalysts, principally rhodium and iridium complexes. We report here that abundant nickel can be paired with imidazole-derived carbenes or the corresponding salts to catalyze methyl ester carbonylation with turnover frequency (TOF) exceeding 150 hour–1 and turnover number (TON) exceeding 1600, benchmarks that invite comparisons to state-of-the-art rhodium-based systems and considerably surpass known triphenylphosphine-based nickel catalysts, which operate with TOF ~7 hour–1 and TON ~100 under the same conditions. [ABSTRACT FROM AUTHOR]

Rhodium‐catalyzed Sommelet‐Hauser rearrangement derived from α‐thioesters/α‐selenoesters and sulfoxonium ylides has been developed for the synthesis of various sulfur/selenium‐containing ortho‐substituted aromatic compounds in medium to excellent yields (39 examples; up to 97 %). Sulfoxonium ylides as the safe carbene precursors are firstly used in Sommelet‐Hauser rearrangement reactions, which is superior to traditional diazo compounds. The present reaction has the advantages of mild condition, safety and broad substrate scope, which afford a unique method for the synthesis of sulfur/selenium‐containing compounds with a tertiary carbon center. [ABSTRACT FROM AUTHOR]

The sigma amine−borane complexes [Rh(L1)(η2:η2‐H3B⋅NRH2)][OTf] (L1=2,6‐bis‐[1‐(2,6‐diisopropylphenylimino)ethyl]pyridine, R=Me, Et, nPr) are described, alongside [Rh(L1)(NMeH2)][OTf]. Using R=Me as a pre‐catalyst (1 mol %) the dehydropolymerization of H3B ⋅ NMeH2 gives [H2BNMeH]n selectively. Added NMeH2, or the direct use of [Rh(L1)(NMeH2)][OTf], is required for initiation of catalysis, which is suggested to operate through the formation of a neutral hydride complex, Rh(L1)H. The formation of small (1–5 nm) nanoparticles is observed at the end of catalysis, but studies are ambiguous as to whether the catalysis is solely nanoparticle promoted or if there is a molecular homogeneous component. [Rh(L1)(NMeH2)][OTf] is shown to operate at 0.025 mol % loadings on a 2 g scale of H3B ⋅ NMeH2 to give polyaminoborane [H2BNMeH]n [Mn=30,900 g/mol, Ð=1.8] that can be purified to a low residual [Rh] (6 μg/g). Addition of Na[N(SiMe3)2] to [H2BNMeH]n results in selective depolymerization to form the eee‐isomer of N,N,N‐trimethylcyclotriborazane [H2BNMeH]3: the chemical repurposing of a main‐group polymer. [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]

Rh-dispersed Cu Nanowires Catalyst has been designed for cathodic catalytic conversion of 5-hydroxymethylfurfural (HMF) to 2,5-bis(hydroxymethyl)furan (BHMF). Rh component boosts the proportion of ordered weakly hydrogen-bonded water molecules on the catalyst surface, accelerating the water dissociation and facilitating the generation of reactive hydrogen (H ads), thus improving the selectivity of BHMF. [Display omitted] Electrocatalytic conversion of biomass-derived 5-hydroxymethylfurfural (HMF) to 2,5-bis(hydroxymethyl)furan (BHMF) presents a compelling strategy for the production of premium chemicals via the utilization of renewable energy sources. Exploring efficient catalytic systems to obtain highly selective BHMF has remained a giant challenge. A design strategy is proposed here to regulate active hydrogen (H ads) production in rhodium (Rh) nanoparticles grown on Cu nanowires (RhCu NWs) catalyst, which achieves a faradaic efficiency (FE) of 92.6% in the electrocatalytic reduction of HMF to BHMF at −20 mA cm−2 with no degradation in performance after 8 cycles. Kinetic investigations and electron spin resonance (ESR) spectroscopy reveal that the incorporation of Rh accelerates the water dissociation and facilitates the generation of H ads. In situ attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) further demonstrates that the Rh component boosts the proportion of ordered weakly hydrogen-bonded water molecules on the catalyst surface, which is much easier to dissociate. The construction of an interfacial H ads -rich environment promotes the HMF intermediates binding with H ads to BMHF, thereby suppressing the formation of undesired dimers. This work demonstrates the promise of altering the interfacial water environment as a strategy to boost the electrosynthetic properties of biomass-derived products toward value-added outcomes. [ABSTRACT FROM AUTHOR]

A rhodium(III)-catalyzed redox-neutral spiroannulation approach to access the spiro[benzo[b][1,4]oxazine-benzo[c]chromene skeleton is described in this contribution. A variety of spiro[5.5]-heterocyclic scaffolds were obtained in moderate to excellent yields under mild conditions. Key features of this protocol are good substrate scope, silver-free conditions, low catalyst loadings, easy handling under air and 100% atom economy. Furthermore, scale-up reactions and late-stage derivatizations highlight the potential synthetic utility of this methodology. [ABSTRACT FROM AUTHOR]

Neutral and cationic cyclooctadiene rhodium(I) complexes with a lutidine-derived polydentate ligand having NHC and methoxy side-donor functions, [RhBr(cod)(κC-tBuImCH2PyCH2OMe)] and [Rh(cod)(κ2C,N-tBuImCH2PyCH2OMe)]PF6, have been prepared. Carbonylation of the cationic compound yields the dicarbonyl complex [Rh(CO)2(κ2C,N-tBuImCH2PyCH2OMe)]PF6 whereas carbonylation of the neutral compound affords a mixture of di- and monocarbonyl neutral complexes [RhBr(CO)2(κC-tBuImCH2PyCH2OMe)] and [RhBr(CO)(κ2C,N-tBuImCH2PyCH2OMe)]. These complexes efficiently catalyze the hydrosilylation of 1-hexyne with HSiMe2Ph with a marked selectivity towards the β-(Z)-vinylsilane product. Catalyst [RhBr(CO)(κ2C,N-tBuImCH2PyCH2OMe)] showed a superior catalytic performance, in terms of both activity and selectivity, and has been applied to the hydrosilylation of a range of 1-alkynes and phenylacetylene derivatives with diverse hydrosilanes, including HSiMe2Ph, HSiMePh2, HSiPh3 and HSiEt3, showing excellent β-(Z) selectivity for the hydrosilylation of linear aliphatic 1-alkynes. Hydrosilylation of internal alkynes, such as diphenylacetylene and 1-phenyl-1-propyne, selectively affords the syn-addition vinylsilane products. The β-(Z) selectivity of these catalysts contrasts with that of related rhodium(I) catalysts based on 2-picolyl-functionalised NHC ligands, which were reported to be β-(E) selective. An energy barrier ΔG‡ of 19.8 ± 2.0 kcal mol−1 (298 K) has been determined from kinetic studies on the hydrosilylation of 1-hexyne with HSiMe2Ph. DFT studies suggest that the methoxy-methyl group is unlikely to be involved in the activation of hydrosilane, and then hydrosilane activation is likely to proceed via a classical Si–H oxidative addition. [ABSTRACT FROM AUTHOR]

Rhodium‐catalyzed hydroformylation of olefins is an important method for synthesizing aldehydes, and it is worth noting that regioselectivity and enantioselectivity of the product controlled by ligand are the most commonly used strategies. The modular synthesis of phosphite and phosphoramidite ligands have significant advantages of simple synthesis and high catalytic activity, which was why these ligands have been widely used in hydroformylation reactions. Herein, we focus on the synthesis methods and design ideas of such ligands, as well as their application effects in hydroformylation reactions. This review aims to provide a reference for the design and synthesis of ligands in hydroformylation subsequently. [ABSTRACT FROM AUTHOR]

The unsymmetrical diborane(4) derivative [(d(CH2P(iPr)2)abB)–Bpin] (1) proved to be a versatile PBP boryl pincer ligand precursor for Co(I) (2a, 4a), Rh(I) (2–3b) and Ir(I/III) (2–3c, 5–6c) complexes, in particular of the types [(d(CH2P(iPr)2)abB)M(PMe3)2] (2a–c) and [(d(CH2P(iPr)2)abB)M–PMe3] (2b–c). Whilst similar complexes have been obtained before, for the first time, the coordination chemistry of a homologous series of PBP pincer complexes, in particular the interconversion of the five- and four-coordinate complexes 2a–c/3a–c, was studied in detail. For Co, instead of the mono phosphine complex 2a, the dinitrogen complex [(d(CH2P(iPr)2)abB)Co(N2)(PMe3)] (4a) is formed spontaneously upon PMe3 abstraction from 2a in the presence of N2. All complexes were comprehensively characterised spectroscopically in solution via multinuclear (VT-)NMR spectroscopy and structurally in the solid state through single-crystal X-ray diffraction. The unique properties of the PBP ligand with respect to its coordination chemical properties are addressed. [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]

Cadmium(II) complexes with thiolate ligands have received considerable attention because of their intriguing structural features and relevance to metalloproteins. In this study, a new cadmium(II)–rhodium(III) trinuclear complex, [Cd{Rh(apt)3}2]Br2·4H2O (1, apt = 3-aminopropanethiolate), was synthesized by the reaction of fac-[Rh(apt)3] with cadmium bromide. Compound 1 was characterized using elemental analysis, X-ray fluorescence and IR spectroscopies, and powder X-ray diffraction study. Single-crystal X-ray analysis revealed that the cadmium(II) center in 1 was surrounded by six thiolato S atoms from two fac-[Rh(apt)3] units. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of four compounds [M(η5‐C5Me5)(N^N)Cl]PF6 [N^N=4,7‐dichloro‐1,10‐phenanthroline with M=Rh, 1, and M=Ir, 2, and N^N=4'‐(4‐chlorophenyl)‐2,2':6',2''‐terpyridine in the κ2N,N'‐coordination mode with M=Rh, 3, and M=Ir, 4] are described. All compounds were characterized by spectroscopic means and their molecular structures in the crystal were confirmed by single‐crystal X‐ray diffraction studies. The cytotoxicity of all compounds was evaluated by MTT assay against the three cancer cell lines HeLa (cervical carcinoma), HT‐29 (colon adenocarcinoma) and MCF‐7 (human breast adenocarcinoma). The complexes 3 and 4 display promising activity with IC50 values of 1 μM. The rhodium(III) complex 1 also shows highly improved cytotoxicity compared to cisplatin against the cancer cell lines HT‐29 and MCF‐7. In contrast to this, the iridium(III) complex 2 is even less active against the HeLa cell line than cisplatin. [ABSTRACT FROM AUTHOR]

Schiff bases containing selenium donor sites are emerging as a prominent class of ligands used for homogeneous catalysis. Such ligands are designed using various routes. However, the most frequently utilized route for the synthesis of such ligands is condensation reaction between primary amines (having Se donor sites) and carbonyl compounds. Selenium donor sites are incorporated in the framework of primary amines via nucleophilic substitution reaction between the chloro derivative of alkanamine and PhSeNa. A variety of such Schiff bases have been used to obtain the metal complexes of various metals (such as palladium, ruthenium, platinum, rhodium, and iridium). These metal complexes have the potential to catalyse different organic reactions, such as Suzuki coupling reaction, Heck coupling reaction, Sonogashira coupling reaction, transfer hydrogenation reaction, O-arylation of phenol, and oxidation of alcohols. This article covers important synthetic methodologies used in designing Schiff bases containing Se donor sites and their catalytically active metal complexes. The most significant component of this article is the critical analysis of the applications of such complexes in homogeneous catalysis of various chemical transformations. Substrate scopes have been analyzed. Factors which are responsible for variations in catalytic performances (on the basis of TON and % conversion/yield) have been highlighted. Some light has also been thrown on the mechanistic aspects of catalysis. Conclusions and future perspectives of the field have also been discussed. [ABSTRACT FROM AUTHOR]

The tandem isomerization–hydrosilylation reaction is a highly valuable process able to transform mixtures of internal olefins into linear silanes. Unsaturated and cationic hydrido-silyl-Rh(III) complexes have proven to be effective catalysts for this reaction. Herein, three silicon-based bidentate ligands, 8-(dimethylsilyl)quinoline (L1), 8-(dimethylsilyl)-2-methylquinoline (L2) and 4-(dimethylsilyl)-9-phenylacridine (L3), have been used to synthesize three neutral [RhCl(H)(L)PPh3] (1-L1, 1-L2 and 1-L3) and three cationic [Rh(H)(L)(PPh3)2][BArF4] (2-L1, 2-L2 and 2-L3) Rh(III) complexes. Among the neutral compounds, 1-L2 could be characterized in the solid state by X-ray diffraction showing a distorted trigonal bipyramidal structure. Neutral complexes (1-L1, 1-L2 and 1-L3) failed to catalyze the hydrosilylation of olefins. On the other hand, the cationic compound 2-L2 was also characterized by X-ray diffraction showing a square pyramidal structure. The unsaturated and cationic Rh(III) complexes 2-L1, 2-L2 and 2-L3 showed significant catalytic activity in the hydrosilylation of remote alkenes, with the most sterically hindered (2-L2) being the most active one. [ABSTRACT FROM AUTHOR]

Herein we report an improved self‐assembling phosphorus ligand based on hydrogen bonding between pyridone/hydroxypyridine in the ligand backbone. The N‐pyrrolyl substituents significantly improve the π‐backbonding properties of the ligand. Rhodium, iridium and platinum complexes of the ligand were prepared and analyzed by NMR spectroscopy and x‐ray crystal structure analysis. A catalyst based on this ligand showed very high catalytic activity and linear regioselectivity in rhodium‐catalyzed hydroformylation of 1‐octene. The same ligand was applied in linear regioselective iridium‐catalyzed hydroformylation of 1‐octene. [ABSTRACT FROM AUTHOR]

Rh(III)‐catalyzed cascade oxidative C−H functionalization/aza‐annulation of indole and pyrrole‐N‐carboxamides with 1,3‐enynes involving 1,4‐rhodium migration is disclosed. This [4+1] annulation protocol provides an approach for the synthesis of imidazo[1,5‐a]indol‐3(2H)‐ones from easily accessible substrates. Moreover, sulfonamides are also found to be well compatible in this method, leading to the corresponding benzo[d]sultams. The efficacy of this protocol is highlighted by handy downstream conversions of the dienyl‐sultam. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of new and easily tunable diphosphine ligands have been synthesized. • Product selectivity in hydroformylation of strained dialkenes can be controlled. • Coordination modes of Rh complexes bearing the new ligand are analyzed. • Ligand effects on product selectivity and complex coordination modes are mentioned. We reported the synthesis of new and easily tunable diphosphine ligands L1 - L5 based on bis(1H-indol-3-yl)methane. Strained 2,5-norbornadiene and dicyclopentadiene were used as the substrates to elucidate the relationship between ligand structure and product selectivity in Rh-catalyzed hydroformylation. Details in NMR, HRMS and single-crystal X-ray diffraction revealed that the coordination number and oxidation state could change rapidly upon exposure of RhI- L complexes to air. More importantly, the special structure of ligand which led to intramolecular methylene C–H oxidative addition to metal center could facilitate the hydroformylation reaction in an unexpected way. [ABSTRACT FROM AUTHOR]