Rh Cl Research Articles

Chloride‐Assisted Transfer Hydrogenation of Ketones by Half‐Sandwich Rhodium Iminophosphonamide Complexes

Half‐sandwich 18e rhodium iminophosphonamide complexes [Сp*RhCl(NPN)] with NPN = Ph2P(N‐p‐Tol)2 (1a), Ph2P(N‐p‐Tol)(NMe) (1b) and 16e cationic [Сp*Rh(NPN)](PF6) (2a+PF6‐) were found to catalyze transfer hydrogenation of carbonylic substrates (acyclic and cyclic alkyl ketones, aromatic ketones and aldehydes) with the activity strongly enhanced by the presence of chloride ligand. Kinetic studies including KIE and activation parameters measurements carried out for two model ketones (acetophenone and cyclohexanone) as well as model spectroscopic investigation accompanied with the DFT calculations allowed to propose unconventional chloride‐assisted mechanism of transfer hydrogenation to account for different behavior of 18e chloride complexes vs their less active 16e cationic counterparts. The key species initiating the catalytic cycle is the solvate complex [Cp*Rh(NPN)(iPrOH)]Cl, which does not result from direct coordination of iPrOH to 2a+PF6‐ rather forms via the Cl‐ dissociation in 1 promoted by specific interactions with alcohol, namely by H‐bonding with the Cl ligand, Cp*Rh(NPN)Cl···HOR.

Sonoactivated Z-Scheme Heterojunction for Enhanced Sonodynamic Mitophagy Inhibition and Triple Negative Breast Cancer Treatment.

Sonodynamic therapy (SDT) has emerged as a potent therapeutic modality to generate intratumoral toxic reactive oxygen species (ROS) in combating refractory triple-negative breast cancer (TNBC). However, its therapeutic efficacy is compromised due to pro-survival cancer-cell mitophagy to mitigate mitochondrial oxidative damage. Here, an "all-in-one" tumor-therapeutic strategy that integrates nanosonosensitizer-augmented noninvasive SDT with mitophagy inhibition is reported. This is achieved using a rationally constructed sonoactivated liquid Z-scheme heterojunction that connects sonosensitizer PtCu3 nanocages and mitophagy-blocking sonosensitizer BP nanosheets via an amphipathic organic linker (PEI-PEG5000-C18). The conjugated electron mediator (M, Cp*Rh(phen)Cl) is strategically positioned between the 2 sonosensitizers to facilitate electron transfer. This M-based Z-scheme configuration prolongs the separation of sonoactivated electron-hole pairs, leading to efficient ROS generation upon ultrasound stimulation. Importantly, Cu2+ released from PtCu3 expedites BP degradation by reducing phosphorus vacancy formation energy, improving the overall biodegradability of BP-M-PtCu3 and favoring phosphate ions production. These ions elevate lysosomal pH, inhibiting the hydrolysis of damaged mitochondria within autophagic lysosomes, thus preventing cancer cell self-preservation under oxidative stress and effectively eliminating TNBC. It is believe that the M-based sonoactivated Z-scheme heterojunction will be a promising sonosensitizer structure, and the sonodynamic mitophagy inhibition strategy offers valuable prospects for cancer treatment.

Biomass betulin-based porous aromatic frameworks nanomicrospheres as adsorbents for reversible capture of iodine

Betulin with a modifiable hydroxyl group and a rigid backbone is a kind of natural triterpene product that extracted from white barked birch bark with up to 30 % of its dry weight. Herin, we prepared a series of betulin-based porous aromatic frameworks (BEPAFs) nanomicrospheres by [Rh(nbd)Cl]2 polymerization or Sonogashira-Hagihara coupling reaction for iodine vapor capture and adsorption. The resulting BEPAFs nanomicrospheres presented perfect thermal stability and high specific surface areas that up to 324.6 m2 g−1, 506.3 m2 g−1 and 320.5 m2 g−1 for BEPAF-1, BEPAF-2 and BEPAF-3, respectively. Based on the above characteristics, the BEPFAs nanomicrospheres showed an excellent iodine capture performance with the volatile iodine capture ability reached 3.79 g g−1 and iodine adsorption in cyclohexane solution up to 389.9 mg g−1. The iodine capture behavior is consistent with the pseudo-second-order model, indicating that the iodine adsorption process of BEPAFs microspheres belongs to multilayer heterogeneous surface chemical adsorption. Furthermore, the BEPFAs nanomicrospheres could maintained 88.26 % of the absorption capacity after four cycles that endow them a great potential in practical application. This research provides a facile synthesis of biomass porous aromatic framework nanomicrospheres adsorbents based on the natural product.

Macrobicyclic Dibridgehead Di(trialkyl)pnictogens E((CH2) n )3E (E/n = As/10, As/12, As/14, Sb/14) and Their Cage-like Metal Complexes: Syntheses, Structures, and Homeomorphic Isomerizations.

Photolyses of trans-Fe(CO)3(As((CH2) n )3As) (n = a, 10; b, 12; c, 14) in the presence of PMe3, or reactions of trans-[Fe(CO)2(NO)(As((CH2) n )3As)]+ BF4 - and n-Bu4N+ Cl-, afford the air stable title complexes As((CH2) n )3As (8a-c) in 79-34% yields. With 8a, the in, in and out, out isomers are separable and each is crystallographically characterized. With 8b,c, the isomers rapidly interconvert by homeomorphic isomerization, but each crystallizes (contrathermodynamically) as an out, out isomer. Reactions of 8c with H2O2 or 8b with BH3 give 8c·2O or 8b·2BH3, respectively (85-94%). Reactions of 8c with MCl2 (M = Pt, Pd, Ni), Rh(CO)(Cl), and Fe(CO)3 sources afford the corresponding cage-like complexes trans-ML n (As((CH2)14)3As) (86-51%). The crystal structures of 8c·2O and the PtCl2 and PdCl2 adducts are determined and compared to those of 8a-c and diphosphorus analogs. The corresponding distibine Sb((CH2)14)3Sb is analogously prepared, but precursors necessary for the bismuth analog could not be accessed due to the diminished BiR3 Lewis basicity.

Catalytic Kinetic Resolution of Monohydrosilanes via Rhodium-Catalyzed Enantioselective Intramolecular Hydrosilylation.

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.

Catalytic Kinetic Resolution of Monohydrosilanes via Rhodium‐Catalyzed Enantioselective Intramolecular Hydrosilylation

AbstractThe 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.

Arene Reduction by Rh/Pd or Rh/Pt under 1 atm Hydrogen Gas and Room Temperature.

Current methods for arene hydrogenation generally need either harsh reaction conditions or complex catalyst preparation. Here we describe a mild and convenient protocol that only utilizes commercially available catalysts. Using [Rh(nbd)Cl]2 and Pd/C together as catalysts, arenes bearing various functional groups can be hydrogenated under 1 atm of H2 at room temperature. This arene hydrogenation can also be achieved using catalysts of [Rh(cod)Cl]2 and PtO2, thus avoiding glovebox manipulations and simplifying the reaction procedure.

Hydrogenation of Styrene-Butadiene Rubber Catalyzed by Tris(triisopropylphosphine)hydridorhodium(I)

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

A new poly(trialkylsilylethynylphenylacetylene)s membrane toward enhanced oxygen permeability

AbstractPolyacetylenes with good performance in O2/N2 separation were reported. A series of cis‐helical poly(trialkylsilylethynylphenylacetylene)s (PSEPAs) with average molecular weight in the range of 105–106 g mol−1 are synthesized under the catalysis of [Rh(nbd)Cl]2. The free‐standing membranes are prepared from the solution of PSEPAs in chloroform. A rigid PSEPA membrane exhibits the tensile strength of 22.2 MPa, while a flexible PSEPA membrane shows an elongation at break of 44.2% at room temperature. Moreover, the rigid PSEPA membrane shows ultra‐high oxygen permeability of 3.09 × 105 Barrer. The results show that PSEPAs are potential polymers for the applications in O2/N2 separation field.

Intermolecular C-H silylations of arenes and heteroarenes with mono-, bis-, and tris(trimethylsiloxy)hydrosilanes: control of silane redistribution under operationally diverse approaches.

Efficient catalytic protocols for C-H silylations of arenes and heteroarenes with sterically and electronically different hydrosiloxysilanes are disclosed. The silylations are catalyzed by a well-defined Rh-complex (1 mol%), derived from [Rh(1,5-hexadiene)Cl]2 and a bulky BINAP type ligand. This catalyst not only promotes C-Si bond formation affording the desired products in up to 95% isolated yield, but also can suppress the silane redistribution side reactions of HSiMe2(OTMS). The protocol can also be applied for the C-H silylations of more reactive HSiMe(OTMS)2 with a much lower catalyst loading (0.25 mol%) and even with sterically demanding HSi(OTMS)3. The steric bulk of the arene substituent and hydrosiloxysilane is a major factor in determining the regioselectivity and electronic effect as secondary. The current method can be performed under operationally diverse conditions: with/without a hydrogen scavenger or solvent.

Experimental insights into electrocatalytic [Cp*Rh(bpy)Cl]+ mediated NADH regeneration

NADH plays a crucial role in many enzymatically catalysed reactions. Due to the high costs of NADH a regeneration mechanism of this cofactor can enlarge the applications of enzymatic reactions dramatically. This paper gives a thorough system analysis of the mediated electrochemical regeneration of active NADH using cyclic voltammograms and potentiostatic measurements with varying pH, electrode potential, and electrolyte solution, highlighting the system’s limiting conditions, elucidating optimal working parameters for the electrochemical reduction of NAD+, and bringing new insight on the oxidation of inactive reduction products. Using [Cp*Rh(bpy)Cl]+ as an electron mediator dramatically increases the percentage of enzymatically active electrochemically reduced NADH from 15% (direct) to 99% (mediated) with a faradaic efficiency of up to 86%. Furthermore, investigations of the catalytic mechanisms of [Cp*Rh(bpy)Cl]+ clarifies the necessary conditions for its functioning and questions the proposed reaction mechanism by two-step reduction where first the mediator is reduced and then brought in contact with NAD+.

Controlled cluster expansion at a Zintl cluster surface

AbstractReaction of the tris‐hypersilyl nonagermanide Zintl cluster salt, K[Ge9(Hyp)3] (Hyp=Si(SiMe3)3) with [Rh(η2,η2‐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){Ge9(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.

Controlled cluster expansion at a Zintl cluster surface.

Reaction of the tris-hypersilyl nonagermanide Zintl cluster salt, K[Ge9 (Hyp)3 ] (Hyp=Si(SiMe3 )3 ) with [Rh(η2 ,η2 -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){Ge9 (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.

Cytotoxic Activity of Some Half‐sandwich Rhodium(III) Complexes Containing 4,4’‐disubstituted‐2,2’‐bipyridine Ligands

AbstractThe 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.

On K-Banhatti indices and entropy measure for rhodium (III) chloride via linear regression models

Rhodium (III) chloride is a metallic compound characterized by its shiny and silvery-white appearance. It possesses high reflectivity and exhibits excellent resistance to corrosion. This makes it a popular choice for applications such as plating materials in jewelry and other decorative items, imparting a lustrous and reflective surface to the coated objects. Topological indices are numerical parameters employed to characterize the topology of a molecular structure. These indices are derived from the connectivity of atoms within the molecule and serve as predictors for various molecular properties, including reactivity, stability, and solubility. On the other hand, the Shannon entropy of a graph finds extensive applications in network science. It is utilized in the analysis of diverse networks, such as social networks, biological networks, and transportation networks. The Shannon entropy allows for the characterization of a network's topology and structure, aiding in the identification of crucial nodes or structures that play significant roles in network functionality and stability. In this paper, our primary objective is to compute different K-Banhatti indices and employ them to evaluate the entropy measure of Rhodium (III) chloride RhCl3. Additionally, we conducted an examination through linear regression analysis involving various indices and entropies associated with Rhodium chloride. Moreover, we established a correlation between degree-based Banhatti indices and entropies via the line fit method.

Highly selective and recyclable homogeneous hydroformylation of olefins with [Rh(cod)Cl]2/PPh3 regulated by Et3N as additive

Rh-catalyzed hydroformylation of different olefins toward the corresponding aldehydes were performed under syngas atmosphere in the presence of triethylamine (Et3N) as additive. The influence of various reaction parameters including the phosphine ligands, solvents, additives have been investigated. It was found that, by involving Et3N as additive in the [Rh(cod)Cl]2/PPh3 catalytic system, the conversion of substrates (including cyclic, internal and linear olefins, up to 99%) and chemo/regioselectivity of the products were improved (up to 99%), the applicability for the synthesis of important aldehydes was wider in the absence of solvent. More importantly, the catalytic system could be recycled more than 7 times through vacuum distillation operation and provided a new synthesis method for the pesticide dinotefuran (Tetrahydrofuran-3-formaldehyde) and perfume (Lily aldehyde) intermediates.

Rh-Catalyzed [4 + 1] Reaction of Cyclopropyl-Capped Dienes (but not Common Dienes) and Carbon Monoxide: Reaction Development and Mechanistic Study.

Transition-metal-catalyzed [4 + 1] reaction of dienes and carbon monoxide (CO) is the most straightforward and easily envisioned cyclization for the synthesis of five-membered carbocycles, which are ubiquitously found in natural products and functional molecules. Unfortunately, no test of this reaction was reported, and consequently, chemists do not know whether such kind of reaction works or not. Herein, we report that the [4 + 1] reaction of common dienes and CO cannot work, at least under the catalysis of [Rh(cod)Cl]2. However, using cyclopropyl-capped dienes (also named allylidenecyclopropanes) as substrates, the corresponding [4 + 1] reaction with CO proceeds smoothly in the presence of [Rh(cod)Cl]2. This [4 + 1] reaction, with a broad scope, provides efficient access to five-membered carbocyclic compounds of spiro[2.4]hept-6-en-4-ones. The [4 + 1] cycloadducts can be further transformed into other molecules by using the unique chemistry of cyclopropyl groups present in these molecules. The mechanism of this [4 + 1] reaction has been investigated by quantum chemical calculations, uncovering that cyclopropyl-capped dienes are strained dienes and the oxidative cyclization step in the [4 + 1] catalytic cycle can release this (angular) strain both kinetically and thermodynamically. The strain release in this step then propagates to all followed CO coordination/CO insertion/reductive elimination steps in the [4 + 1] catalytic cycle, helping the realization of this cycloaddition reaction. In contrast, common dienes (including cyclobutyl-capped dienes) do not have such advantages and their [4 + 1] reaction suffers from energy penalty in all steps involved in the [4 + 1] catalytic cycle. The reactivity of ene-allenes for the [4 + 1] reaction with CO is also discussed.

Extraction of Rh(III) from hydrochloric acid by protonated NTAamide(C6) and analogous compounds and understanding of extraction equilibria by using UV spectroscopy and DFT calculations.

Extraction of Rh from hydrochloric acid is conducted using NTAamide(C6) (N,N,N´,N´,N´´,N´´-hexahexyl-nitrilotriacetamide) and other related compounds. We use the ion-pair extraction of anionic species of Rh-chloride and protonated extractant. Rh ions exist as Rh(Cl)n(H2O)6-n (n ≤ 5) and the tertiary nitrogen atom in an extractant are protonated to produce a quaternary amine in acidic condition. The D(Rh) values are changeable because the Rh-Cl-H2O complex forms from + 3 to - 2 valency. Rh-chloride ion with a peak of spectrum at 504nm can be extracted effectively, where RhCl4(H2O)- and RhCl5(H2O)2- exist from Density functional theory calculation and UV spectrum. The maximum distribution ratio (D) of Rh(III) is 16, and 85mM Rh can be extracted from 1M HCl dissolving 96mM, due to less third phase formation. Approximate 80% of Rh can be stripped by the water-soluble reagents having the activities of neutralization and solvation. The figure for the Graphical Index saved in the JPEG, PNG or TIFF format at 300 dpi should be pasted with the size adjusted to the frame below (5 cm long and 8 cm wide).

Development of Methods for Controlled Polymerization of Monosubstituted Acetylenes Enabling Versatile Design of Polymer End Structures

Substituted polyacetylene derivatives are promising π-conjugated materials, which can be synthesized by polymerization of the corresponding substituted acetylenes by transition metal catalysis. Rhodium(I) complexes have been widely used for the polymerization of monosubstituted acetylenes such as phenylacetylene derivatives because they are functional group tolerant and provide cis-stereoregular polymers. There are some examples of well-controlled polymerization of phenylacetylene derivatives using well-defined rhodium(I) complexes as initiators. However, versatile design of polymer end structures is difficult in such known methods because initiators having various functional groups are not easily available. To overcome such a problem, we have developed a new method for well-controlled polymerization of phenylacetylene derivatives using a multicomponent catalytic system composed of bicyclo[2.2.1]hepta-2,5-diene-rhodium(I) chloride dimer [Rh(nbd)Cl]2, arylboronic acids, diphenylacetylene and 50% aqueous solution of KOH. This polymerization method showed a typical living nature, and structures derived from aryl boronic acids and diphenylacetylene were introduced to the initiating end of the obtained polymers. Moreover, functionalization of the polymer terminal end could be achieved by reactions of the living polymer terminus with α,β-unsaturated carbonyl compounds such as acrylates, and various telechelic poly(phenylacetylene)s were obtained. Novel 1,3,5-hexatrienylrhodium(I) complexes were isolated from the present multicomponent catalytic system, and their structures were identified. When [Rh(nbd)Cl]2 was replaced with hydroxy(1,5-cyclooctadiene) rhodium(I) dimer ([Rh(cod)OH]2) in the present catalytic system, cyclobutenylrhodium(I) complexes were exclusively obtained. These complexes provided insights into the initiation mechanism in the living polymerization. The present catalytic system was applied to the living polymerization of water-soluble phenylacetylene derivatives and non-conjugated monosubstituted acetylenes such as N-propargylamides.

Phosphine Functionalized CpC Ligands and Their Metal Complexes

Simple nucleophilic aliphatic substitution gives access to mono- and diphosphine ligands with a CpC group in the backbone. The monophosphine ligand coordinates to gold(I) via the phosphine site, to thallium(I) via the cyclopentadienyl site and to ruthenium(II) via a combination of both, resulting in an ansa-type structure. Coordination with the cyclopentadiene site is not possible for the diphosphine ligand. In this case, monodentate coordination to gold(I) and bidentate coordination to the [PdCl(μ2-Cl)]2, the [Rh(CO)(μ2-Cl)]2, and the Rh(CO)Cl fragment is observed, showing the variability in coordination modes possible for the long-chain diphosphine ligand. Ligands and complexes were characterized by means of NMR and IR spectroscopy, elemental analysis and X-ray structure analysis.