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Molecules (Basel, Switzerland) Jan 2021Reactions of cyclometalated compounds are numerous. This account is focused on one of such reactions, the exchange of cyclometalated ligands, a reaction between a... (Review)
Review
Reactions of cyclometalated compounds are numerous. This account is focused on one of such reactions, the exchange of cyclometalated ligands, a reaction between a cyclometalated compound and an incoming ligand that replaces a previously cyclometalated ligand to form a new metalacycle: + H-C*~Z ⇄ + H-C~Y. Originally discovered for Pd complexes with Y/Z = N, P, S, the exchange appeared to be a mechanistically challenging, simple, and convenient routine for the synthesis of cyclopalladated complexes. Over four decades it was expanded to cyclometalated derivatives of platinum, ruthenium, manganese, rhodium, and iridium. The exchange, which is also questionably referred to as transcyclometalation, offers attractive synthetic possibilities and assists in disclosing key mechanistic pathways associated with the C-H bond activation by transition metal complexes and C-M bond cleavage. Both synthetic and mechanistic aspects of the exchange are reviewed and discussed.
Topics: Ligands; Metals; Molecular Structure; Organometallic Compounds
PubMed: 33401624
DOI: 10.3390/molecules26010210 -
IUCrData Apr 2023The mol-ecule of the title compound, [Rh(CHNO){As(CH)}(CO)] or [Rh(BPHA)(AsPh)(CO)] (BPHA is the -benzoyl--phenyl-hydroxy-laminate anion), comprises a bidentate...
The mol-ecule of the title compound, [Rh(CHNO){As(CH)}(CO)] or [Rh(BPHA)(AsPh)(CO)] (BPHA is the -benzoyl--phenyl-hydroxy-laminate anion), comprises a bidentate -benzoyl--phenyl-hydroxy-laminate anion coordinating through the O atoms to the soft Lewis acid, rhodium(I), and two monodentate ligands, . tri-phenyl-arsine and carbonyl. The resulting COAs coordination environment around the central Rh atom is distorted square planar.=.
PubMed: 37151208
DOI: 10.1107/S2414314623003553 -
Arhiv Za Higijenu Rada I Toksikologiju Dec 2019Measurable quantities of platinum, palladium, and rhodium, even in remote areas of the planet, evidence the global nature of pollution with these metals, mostly from... (Review)
Review
Measurable quantities of platinum, palladium, and rhodium, even in remote areas of the planet, evidence the global nature of pollution with these metals, mostly from catalytic converters of modern vehicles (other sources are jewellery production, chemical industry, and anticancer drugs). The amount of the platinum group metals (PGMs) emitted from automobile catalysts varies with the type, age, and condition of the engine and the catalyst, as well as the style of driving. Current literature suggests that the concentrations of these metals have increased considerably over the last twenty years, palladium concentrations in particular, as it has been proved more effective catalyst than platinum. However, whether and to what extent the emitted PGMs are toxic for people is still a controversy. The potential health risk from exposure to these elements is most likely for those living in urban environments with busy roads or along major highways. Because of the importance of PGMs and their trace levels in particulate matter, sensitive methods are required for reliable determination. This review discusses particular steps of analytical procedures for PGM quantification in airborne particulate matter and addresses the common preparation, detection, and determination methods.
Topics: Automobiles; Chemical Industry; Environmental Monitoring; Humans; Palladium; Particulate Matter; Platinum; Rhodium
PubMed: 32623861
DOI: 10.2478/aiht-2019-70-3293 -
Chemistry (Weinheim An Der Bergstrasse,... Aug 2022A family of germyl rhodium complexes derived from the PGeP germylene 2,2'-bis(di-isopropylphosphanylmethyl)-5,5'-dimethyldipyrromethane-1,1'-diylgermanium(II), Ge(pyrmP...
A family of germyl rhodium complexes derived from the PGeP germylene 2,2'-bis(di-isopropylphosphanylmethyl)-5,5'-dimethyldipyrromethane-1,1'-diylgermanium(II), Ge(pyrmP Pr ) CMe (1), has been prepared. Germylene 1 reacted readily with [RhCl(PPh ) ] and [RhCl(cod)(PPh )] (cod=1,5-cyclooctadiene) to give, in both cases, the PGeP-pincer chloridogermyl rhodium(I) derivative [Rh{κ P,Ge,P-GeCl(pyrmP Pr ) CMe }(PPh )] (2). Similarly, the reaction of 1 with [RhCl(cod)(MeCN)] afforded [Rh{κ P,Ge,P-GeCl(pyrmP Pr ) CMe }(MeCN)] (3). The methoxidogermyl and methylgermyl rhodium(I) complexes [Rh{κ P,Ge,P-GeR(pyrmP Pr ) CMe }(PPh )] (R=OMe, 4; Me, 5) were prepared by treating complex 2 with LiOMe and LiMe, respectively. Complex 5 readily reacted with CO to give the carbonyl rhodium(I) derivative [Rh{κ P,Ge,P-GeR(pyrmP Pr ) CMe }(CO)] (6), with HCl, HSnPh and Ph S rendering the pentacoordinate methylgermyl rhodium(III) complexes [RhHX{κ P,Ge,P-GeMe(pyrmP Pr ) CMe }] (X=Cl, 7; SnPh , 8) and [Rh(SPh) {κ P,Ge,P-GeMe(pyrmP Pr ) CMe }] (9), respectively, and with H to give the hexacoordinate derivative [RhH {κ P,Ge,P-GeMe(pyrmP Pr ) CMe }(PPh )] (10). Complexes 3 and 5 are catalyst precursors for the hydroboration of styrene, 4-vinyltoluene and 4-vinylfluorobenzene with catecholborane under mild conditions.
PubMed: 35612568
DOI: 10.1002/chem.202200847 -
Chemistry (Weinheim An Der Bergstrasse,... Apr 2022Tumor associated macrophages (TAMs) suppress the cancer immune response and are a key target for immunotherapy. The effects of ruthenium and rhodium complexes on TAMs...
Tumor associated macrophages (TAMs) suppress the cancer immune response and are a key target for immunotherapy. The effects of ruthenium and rhodium complexes on TAMs have not been well characterized. To address this gap in the field, a panel of 22 dirhodium and ruthenium complexes were screened against three subtypes of macrophages, triple-negative breast cancer and normal breast tissue cells. Experiments were carried out in 2D and biomimetic 3D co-culture experiments with and without irradiation with blue light. Leads were identified with cell-type-specific toxicity toward macrophage subtypes, cancer cells, or both. Experiments with 3D spheroids revealed complexes that sensitized the tumor models to the chemotherapeutic doxorubicin. Cell surface exposure of calreticulin, a known facilitator of immunogenic cell death (ICD), was increased upon treatment, along with a concomitant reduction in the M2-subtype classifier arginase. Our findings lay a strong foundation for the future development of ruthenium- and rhodium-based chemotherapies targeting TAMs.
Topics: Cell Line, Tumor; Humans; Immunotherapy; Rhodium; Ruthenium; Triple Negative Breast Neoplasms; Tumor-Associated Macrophages
PubMed: 35235227
DOI: 10.1002/chem.202104430 -
IUCrData Jun 2021A new -heterocyclic cationic rhodium(I) complex with a tetra-fluorido-borate counter-anion, [Rh(CHN)(CH)(CHP)]BF, has been prepared and structurally characterized. The...
A new -heterocyclic cationic rhodium(I) complex with a tetra-fluorido-borate counter-anion, [Rh(CHN)(CH)(CHP)]BF, has been prepared and structurally characterized. The cationic complex exhibits a distorted square-planar environment around the rhodium(I) ion. Two connections are made from rhodium(I) to the carbon atom of an -heterocylic carbene ligand and to the phospho-rus atom of a tri-phenyl-phosphane ligand. The remaining two coordination sites are made a bidentate inter-action from the two olefinic bonds of cyclo-octa-diene to the rhodium(I) ion. The compound includes an out-sphere tetra-fluorido-borate counter-anion. Within the crystal of the compound exist several weak inter-molecular C-H⋯F inter-actions.
PubMed: 36337330
DOI: 10.1107/S2414314621005976 -
Nature Communications May 2017Mesoporous noble metals are an emerging class of cutting-edge nanostructured catalysts due to their abundant exposed active sites and highly accessible surfaces....
Mesoporous noble metals are an emerging class of cutting-edge nanostructured catalysts due to their abundant exposed active sites and highly accessible surfaces. Although various noble metal (e.g. Pt, Pd and Au) structures have been synthesized by hard- and soft-templating methods, mesoporous rhodium (Rh) nanoparticles have never been generated via chemical reduction, in part due to the relatively high surface energy of rhodium (Rh) metal. Here we describe a simple, scalable route to generate mesoporous Rh by chemical reduction on polymeric micelle templates [poly(ethylene oxide)-b-poly(methyl methacrylate) (PEO-b-PMMA)]. The mesoporous Rh nanoparticles exhibited a ∼2.6 times enhancement for the electrocatalytic oxidation of methanol compared to commercially available Rh catalyst. Surprisingly, the high surface area mesoporous structure of the Rh catalyst was thermally stable up to 400 °C. The combination of high surface area and thermal stability also enables superior catalytic activity for the remediation of nitric oxide (NO) in lean-burn exhaust containing high concentrations of O.
PubMed: 28524873
DOI: 10.1038/ncomms15581 -
Chemistry (Weinheim An Der Bergstrasse,... Mar 2022The use of arylboron reagents in metal-catalyzed domino addition-cyclization reactions is a well-established strategy for the preparation of diverse, highly... (Review)
Review
The use of arylboron reagents in metal-catalyzed domino addition-cyclization reactions is a well-established strategy for the preparation of diverse, highly functionalized carbo- and heterocyclic products. Although rhodium- and palladium-based catalysts have been commonly used for these reactions, more recent work has demonstrated nickel catalysis is also highly effective, in many cases offering unique reactivity and access to products that might otherwise not be readily available. This review gives an overview of nickel-catalyzed arylative cyclizations of alkyne- and allene-tethered electrophiles using arylboron reagents. The scope of the reactions is discussed in detail, and general mechanistic concepts underpinning the processes are described.
Topics: Alkadienes; Alkynes; Catalysis; Cyclization; Indicators and Reagents; Nickel; Rhodium
PubMed: 34986277
DOI: 10.1002/chem.202104230 -
Molecules (Basel, Switzerland) Apr 2021Rhodium is one of the most used metals in catalysis both in laboratory reactions and industrial processes. Despite the extensive exploration on "classical" ligands... (Review)
Review
Rhodium is one of the most used metals in catalysis both in laboratory reactions and industrial processes. Despite the extensive exploration on "classical" ligands carried out during the past decades in the field of rhodium-catalyzed reactions, such as phosphines, and other common types of ligands including N-heterocyclic carbenes, ferrocenes, cyclopentadienyl anion and pentamethylcyclopentadienyl derivatives, etc., there is still lively research activity on this topic, with considerable efforts being made toward the synthesis of new preformed rhodium catalysts that can be both efficient and selective. Although the "golden age" of homogeneous catalysis might seem over, there is still plenty of room for improvement, especially from the point of view of a more sustainable chemistry. In this review, temporally restricted to the analysis of literature during the past five years (2015-2020), the latest findings and trends in the synthesis and applications of Rh(I) complexes to catalysis will be presented. From the analysis of the most recent literature, it seems clear that rhodium-catalyzed processes still represent a stimulating challenge for the metalloorganic chemist that is far from being over.
PubMed: 33925725
DOI: 10.3390/molecules26092553 -
Angewandte Chemie (International Ed. in... Aug 2016Achieving selective C-H activation at a single and strategic site in the presence of multiple C-H bonds can provide a powerful and generally useful retrosynthetic... (Review)
Review
Achieving selective C-H activation at a single and strategic site in the presence of multiple C-H bonds can provide a powerful and generally useful retrosynthetic disconnection. In this context, a directing group serves as a compass to guide the transition metal to C-H bonds by using distance and geometry as powerful recognition parameters to distinguish between proximal and distal C-H bonds. However, the installation and removal of directing groups is a practical drawback. To improve the utility of this approach, one can seek solutions in three directions: 1) Simplifying the directing group, 2) using common functional groups or protecting groups as directing groups, and 3) attaching the directing group to substrates via a transient covalent bond to render the directing group catalytic. This Review describes the rational development of an extremely simple and yet broadly applicable directing group for Pd(II) , Rh(III) , and Ru(II) catalysts, namely the N-methoxy amide (CONHOMe) moiety. Through collective efforts in the community, a wide range of C-H activation transformations using this type of simple directing group have been developed.
Topics: Amides; Carbon; Catalysis; Chemistry Techniques, Synthetic; Hydrocarbons; Hydrogen; Palladium; Rhodium; Ruthenium
PubMed: 27479708
DOI: 10.1002/anie.201600791