Transmetallation Method Research Articles

Pd(II) and trinuclear Ag(I) bis-N-heterocyclic carbene complexes: Synthesis, structural and in vitro anticancer activity

The synthesis and characterization of two Ag(I)- N -heterocyclic carbene complexes 3 and 4 of imidazole-based NHC proligands 1 and 2, respectively, are described. The findings revealed that the choice of the counter ions is crucial, which can lead to different supramolecular architectures. Complex 3 is a trinuclear, whereas its analogue complex 4 is mononuclear. Despite being structurally different entities, these complexes form cis -palladium-NHC complex 5 by trans-metallation method, which is a cis -platinum analogue. All the reported compounds 1-5 were tested for their anticancer activities, where compounds 2 and 3 found more potent than the rest.

Synthesis of Copper/Silver Core/Shell Nanoparticles by a Transmetallation Method

Synthesis of Copper/Silver Core/Shell Nanoparticles by a Transmetallation Method

Selective hydrogenation of nitriles to secondary amines catalyzed by a pyridyl-functionalized and alkenyl-tethered NHC–Ru(II) complex

A set of Co(III) and Ru(II) compounds are synthesized bearing pyridyl-functionalized and alkenyl-tethered N-heterocyclic carbene (NHC) ligand (L1). [CoIII(L1)3](PF6)3 (1) was synthesized by the reaction of [L1H]PF6, Co(OAc)2.4H2O, K2CO3 in tetrahydrofuran (THF) under refluxing condition. [RuIIL1(η6-p-cymene)Cl]PF6 (2) was synthesized via transmetallation method. For both compounds, the NHC ligand chelates the metal through carbene carbon and pyridyl nitrogen whereas the butenyl unit remains free. Compound 2 hydrogenates organic nitriles efficiently providing selectively secondary amines. In the presence of external amines, unsymmetrical secondary amines are also obtained.

Erratum to: N-Propylphthalimide-Substituted Silver(I) N-Heterocyclic Carbene Complexes and Ruthenium(II) N-Heterocyclic Carbene Complexes: Synthesis and Transfer Hydrogenation of Ketones

This study deals with the synthesis of N-propylphthalimide substituted Ag(I)–N-heterocyclic carbene (NHC) complexes and N-propylphthalimide substituted Ru(II)–NHC complexes in the transfer hydrogenation of ketones. The Ag(I)–NHC complexes were synthesized from the imidazolium salts and Ag2O in dichloromethane at room temperature. The Ru(II)–NHC complexes have been prepared from Ag(I)–NHC complexes using transmetallation method. The six N-propylphthalimide substituted Ag(I)–NHC complexes and six N-propylphthalimide substituted Ru(II)–NHC complexes have been characterized by spectroscopic techniques and elemental analyses. N-propylphthalimide substituted Ru(II)–NHC complexes have been analyzed as catalysts for the transfer hydrogenation of ketones and exhibit activity in this reaction. This study deals with the synthesis of N-propylphthalimide substituted Ag(I)-N-heterocyclic carbene (NHC) complexes and N-propylphthalimide substituted Ru(II)–NHC complexes in the transfer hydrogenation of ketones. The Ag(I)–NHC complexes were synthesized from the imidazolium salts and Ag2O in dichloromethane at room temperature. The Ru(II)–NHC complexes have been prepared from Ag(I)–NHC complexes using transmetallation method. The six N-propylphthalimide substituted Ag(I)–NHC complexes and six N-propylphthalimide substituted Ru(II)–NHC complexeshavebeencharacterizedbyspectroscopictechniquesandelementalanalyses. N-propylphthalimide substituted Ru(II)–NHC complexes have been analyzed as catalysts for the transfer hydrogenation of ketones and exhibit activity in this reaction.

2-Methyl-1,4-Benzodioxan Substituted Ag(I)-N-Heterocyclic Carbene Complexes and Ru(II)-N-Heterocyclic Carbene Complexes: Synthesis, Crystal Structure and Transfer Hydrogenation of Aromatic Ketones

In this study a series of unsymmetrically silver(I)-N-heterocyclic carbene (NHC) and ruthenium(II)-NHC complexes were synthesised. The Ag(I)-NHC complexes (1a-f) were synthesized in dichloromethane at room temperature from the imidazolium salts and Ag2O. The Ru(II)-NHC complexes (2a-f) were prepared from Ag(I)-NHC complexes by using transmetallation method. All compounds were characterized by spectroscopic techniques (NMR and FT-IR) and elemental analyses. The catalytic activities of the Ru(II)-NHC complexes that were investigated in the transfer hydrogenation reactions showed excellent activity. Also, the 2a complex was characterized by single crystal X-ray crystallography. The Ru atom in the 2a complex, [RuCl2(η6-C10H14)(C19H20N2O2)] exhibit a pseudo-octahedral geometry, with the arene occupying three adjacent sites of the octahedron, two Cl atoms and one carbene group. The six-membered ring of the p-cymene is essentially planar [rms deviation=0.008 A].

Improvement on electrochemical performance by partial replacement of Ru@Pt core-shell nanocatalyst by temperature modification

In this paper, the homemade open-loop reduction system (OLRS), and redox transmetalation method were utilized to produce the core-shell Ru (ruthenium)/Pt (platinum) catalysts on the carbon cloth (CC) for direct methanol fuel cell (DMFC) application. By adjusting pH value and heating to proper temperature of the ionized reduction environment, Pt4+ can be first converted into Pt2+ to allow partial Ru replacement with Pt by redox transmetalation and produce Ru@Pt core-shell nanostructures[1]. And we change the reduction temperature to see how it affects the efficiency of the DMFC.The scanning electron microscopic (SEM) top-view micrographs showing that the apparent Ru@Pt nanoparticles successfully deposited on both the inner and outer surfaces of the hydrophilically-treated CC. At high SEM magnification, the small size and high-density distribution of the Ru@Pt nanoparticles were clearly observed on the hydrophilically-treated CC, and much more Pt@Ru catalyst deposit on the CC surface with the sample of 80 °C. The electrosorption charges of hydrogen ion (QH) and the peak current density (IP) of the samples in the cyclic voltammetry (CV) curves. The magnitude of peak current density is positive correlation to the temperature. However, the CO tolerance, indicated that the better CO tolerance contributed to the less Pt replace on Ru cluster, which allow the Ru oxidizing CO to CO2 efficiently, is negative correlation-- to the temperature. The sample of 50 °C shows the better combination catalyst efficiency between the CO tolerance and the electrochemical performance.

Backbone Thio-Functionalized Imidazol-2-ylidene–Metal Complexes: Synthesis, Structure, Electronic Properties, and Catalytic Activity

A new synthetic route to prepare imidazolium salts with heteroatom-containing functional groups at the backbone has been reported. Accordingly, the first example of a backbone bis-thiofunctionalized imidazolium salt (4) was prepared by sequential metal–halogen exchange reaction of 1-methyl-4,5-diiodoimidazole (1) followed by a quaternization reaction with methyl iodide. The metal–carbene complexes 6, 8, and 10 were synthesized conveniently through three different routes, namely, (a) an in situ generated carbene route, (b) a transmetalation method, and (c) direct reaction with a basic metal precursor, and structurally characterized. Subsequently the electronic properties of the newly prepared 1,3-dimethyl-4,5-bis(phenylthio)-imidazol-2-ylidene ((SPh)2IMe) was studied by measuring the carbonyl stretching frequency of the corresponding [Ir{(SPh)2IMe}(CO)2(Cl)] complex. In addition, the air-stable palladium–NHC complex 10 was found to be catalytically active in Suzuki–Miyaura coupling reactions of aryl bromides.

Coordination Singularities of a Bis(p-xylyl)bis(benzimidazolylidene) Ligand and the Bis-iridium and -rhodium-Related Complexes

The reaction of bis(α,α′-p-xylyl)bis(benzimidazolium) dichloride with [IrCp*Cl2]2 or [RhCl(COD)]2 affords the corresponding dimetallic bis-N-heterocyclic carbene complexes of Ir and Rh. The reaction with the iridium complex occurs by the transmetalation method, in the presence of Ag2O, while the reaction with the rhodium complex is carried out in the presence of NaOtBu. The two complexes display an anti configuration of the bis-NHC ligand, with the two metal atoms pointing at different faces of the bis-carbene ligand. In both complexes, the two metal fragments disclose different coordination environments (in–out, with respect to the inner and outer part of the cyclophane-bis-NHC), as a consequence of noncovalent interactions. DFT calculations have been used to rationalize this “less intuitive” coordination singularity. The reaction of the bis(α,α′-p-xylyl)bis(benzimidazolium) dichloride with [RhCl(CO)2]2 in the presence of Ag2O affords a dirhodium complex in which the two metals are on the same side of the ligand, which adopts a syn conformation. In the latter case, the two metals are bridged by a chloride and hydroxyl ligands, therefore facilitating the syn disposition of the ligand.

Synthesis and structural characterization of cis isomer of 1,2,3-triazol-5-ylidene based palladium complexes

A palladium complex (3) of abnormal N-heterocyclic carbene (NHC) namely, 4-(hydroxymethyl)-3-methyl-1-phenyl-1H-1,2,3-triazol-5-ylidene was prepared via silver carbene transmetalation method and characterized by spectroscopic and single crystal XRD data. Single crystal analysis revealed the structure of the complex 3 to be a cis isomer. The synthesis of palladium complex 6via silver carbene transmetalation method led to a mixture of cis–trans isomers. In this case trans isomer was formed as major product. We have reported earlier the synthesis and structural characterization of trans isomer (trans-6). However, the presence of cis isomer was not recognized until the crude reaction mixture was recrystallized from acetonitrile. Pure cis isomer (cis-6) was obtained by washing the cis–trans mixture with acetonitrile followed by slow evaporation of acetonitrile solution at 35 °C. Structure of cis (cis-6) isomer was unambiguously established by single crystal XRD data.

Synthetic strategy of diflurophosphate-bridged bimetallic N-heterocyclic carbene complexes: Synthesis, structures and photoluminescence of picolyl-substituted alkylbenzimidazolylidene ligands

Starting from the proligands 1-methyl-3-picolylbenzimidazoliumhexaflurophosphate (1) and 1-benzyl-3-picolylbenzimidazoliumhexaflurophosphate (2) Ag(I)–NHC complexes, 1-methyl-3-picolylbenz-imidazolylidenesilver(I)hexaflurophosphate (3) and 1-benzyl-3-picolylbenzimidazolylidenesilver(I)hexaflurophosphate (4) have been synthesized. PO2F2 bridged Ag(I)-bimetallic system (5 and 6) developed from 3 and 4 after treatment of AgPF6 and water. 1-Methyl-3-picolyl-benzimidazolylidene-gold(I)hexaflurophosphate(7) and 1-benzyl-3-picolylbenzimidazolylidenegold(I)hexaflurophosphate (8) have been synthesized by Ag–carbene transmetallation method. Further reaction of AgPF6 with 7 and 8 build up the heterobimetallic Ag(I)–Au(I) systems (9 and 10); significantly, PO2F2 unit holds two heterobimetallic Ag(I)–Au(I) units together. Solid state structures of 3, 5, 8 and 9 have been determined by X-ray diffraction studies. Closed shell d10–d10 interactions are ascertained by the luminescence of bimetallic systems 7–10 upon irradiation of UV light.

ChemInform Abstract: Preparative Routes to Organozinc Reagents Used for Organic Synthesis

Organozinc reagents have become extremely important synthetic tools in recent years, and the useful and practical preparative routes to such reagents have been reviewed. The methods have been classified into four broad categories, (1) oxidative zincation method, (2) transmetalation method, (3) halogenzinc exchange, and (4) others. Each categories are subdivided according to the type of organic groups on the zinc atom (alkyl, alkenyl, etc.).

Nanometre Ni and core/shell Ni/Au nanoparticles with controllable dimensions synthesized in reverse microemulsion

Ni nanoparticles with different diameters were chemically synthesized in reverse microemulsion. Furthermore, core/shell Ni/Au nanoparticles with different core diameters and shell thickness were chemically synthesized from the above Ni nanoparticles through an in situ redox–transmetalation method in reverse microemulsion. The X-ray diffraction patterns revealed the presence of crystalline nickel and gold of the core/shell Ni/Au nanoparticles. The spherical Ni nanoparticles and the core/shell structured Ni/Au nanoparticles could be clearly observed by the transmission electron microscope. The diameter of the Ni nanoparticles with narrow size distribution could be controlled to range from about 8 to 30 nm. The diameter of the core/shell Ni/Au nanoparticles could be controlled to range from about 14 to 30 nm, with about 7–21 nm core diameter and about 3–7 nm shell thickness. The ZFC (zero-field-cooled) and FC (field-cooled) curves of the core/shell Ni/Au nanoparticles indicated that the blocking temperature increased from 16 to 53 K as the diameter of the Ni cores increased from about 7 to 15 nm.

有機ホウ素化合物の触媒的有機合成化学

In this review, particular attention will be given to the synthesis of organoboron compounds via the metal-catalyzed addition and coupling reactions, and their synthetic applications in organic syntheses. The traditional methods for the synthesis of organoboron compounds are based on the reaction of trialkyl borates with Grignard or lithium reagents (transmetalation) or the addition of H-B reagents to alkenes or alkynes (uncatalyzed hydroboration). Although these methods are now most common and convenient for large-scale preparations, the metal-catalyzed reactions are advantageous in terms of efficiency and selectivity of the transformations. Hydroboration of alkenes and alkynes is one of the most studied of reactions in the synthesis of organoboron compounds and their application to organic synthesis. However, the catalyzed hydroboration to be a more interesting strategy to realize the different chemo-, regio-, diastereo-, and enantioselectivities, relative to the uncatalyzed reaction. The cross-coupling reaction of metal-boryl reagents is an alternative to the transmetalation method and perhaps a more convenient and direct protocol for the synthesis of organoboron compounds from organic halides and aromatic C-H bond. Much attention has been recently focused on organoboronic acids and their esters due to their practical usefulness for synthetic organic reactions including asymmetric synthesis, combinatorial synthesis, and polymer synthesis, molecular recognition such as host-guest compounds, and neutron capture therapy in treatment of malignant melanoma and brain tumor. New synthetic procedures reviewed in this article will serve to find further applications of organoboron compounds.

Fluorinated Stannanes. Part 2. The Stereospecific Synthesis of Fluorinated Stannanes via a Barbier‐Type Reaction Between Fluorinated Halides and Tributyltin Chloride Mediated by Zinc or Cadmium.

Abstract Fluorinated stannanes are valuable synthons in synthetic organofluorine chemistry. Fluorinated vinyl, alkyl and aryl halides reacted efficiently with tri- n -butyltin chloride in the presence of zinc or cadmium to yield the corresponding stannanes in good yields. In some cases, yield of the stannanes showed a dramatic improvement over the transmetalation method. In all other cases, comparable yields were obtained.

Fluorinated stannanes: Part 2. The stereospecific synthesis of fluorinated stannanes via a Barbier-type reaction between fluorinated halides and tributyltin chloride mediated by zinc or cadmium

Fluorinated stannanes are valuable synthons in synthetic organofluorine chemistry. Fluorinated vinyl, alkyl and aryl halides reacted efficiently with tri- n-butyltin chloride in the presence of zinc or cadmium to yield the corresponding stannanes in good yields. In some cases, yield of the stannanes showed a dramatic improvement over the transmetalation method. In all other cases, comparable yields were obtained.

有機亜鉛試薬の調製法

Organozinc reagents have become extremely important synthetic tools in recent years, and the useful and practical preparative routes to such reagents have been reviewed. The methods have been classified into four broad categories, (1) oxidative zincation method, (2) transmetalation method, (3) halogenzinc exchange, and (4) others. Each categories are subdivided according to the type of organic groups on the zinc atom (alkyl, alkenyl, etc.).

Equilibrium nh acidity of benzenesulfonamide and its derivatives in dimethyl sulfoxide

1. The equilibrium NH acidities of benzenesulfonamide and its derivatives have been studied by the transmetallation method in DMSO. 2. Linear relationships connecting the pK values of benzenesulfonamides C6H5SO2NHR with the σ* constants of alkyl groups R and of substituted benzenesulfonanilides C6H5SO2NHC6H4R′ with the σ constants of the substituents R′ have been found. The acidifying effect of the phenylsulfonyl group on its introduction into aniline and into 4-aminopyridine has been evaluated. 3. A linear relationship has been established between the pK values of anilines and 4-anilinopyridines substituted in the amino groups, and on this basis the presumed pK values of a number of aminopyridine derivatives in DMSO have been calculated.

Pyrroles from ketoximes and acetylene. 14. Quantitative estimate of the effect of substituents on the NH acidities of pyrroles

The pK values of a series of substituted pyrroles and the ΔvNH values (in dimethylformamide), which characterize their relative acidities were measured by the transmetallation method. It was established that the acidities of pyrroles are determined primarily by the inductive effect of the substituents and are virtually independent of the ability of the latter to enter into conjugation with the ring. This means that the electron pair of the anion that is set free in the ionization of pyrrole retains σ character. The linear dependences of the pK and ΔυNH values on the inductive constants (σI) of the substituents can be used to estimate the pK values of various compounds that contain a pyrrole ring starting from the ΔυNH and σI values.

Equilibrium acidity of certain phosphoryl and thiophosphoryl PH-acids in dimethyl sulfoxide

1. The transmetallation method has been used to measure equilibrium acidities of P(O)H-and P(S)H-acids of various structures in dimethylsulfoxide solution and relative to 9-phenyl-fluorene. 2. The effect of the substituent at the P atom on the pK value for the P(O)H-acid can be described by linear correlation relations in the σφ and σ* constants. The diarylphosphinous acids cannot be fitted into such correlations because of p,π coupling in their anions. 3. The acidity of the P(S)H-acids is some nine orders higher than that of the phosphoryl analogs.

Equilibrium CH acidity of boron-substituted carboranes

The results of measuring the equilibrium CH acidity of boron-substituted carboranes-12 by the transmetalation method in 1,2-dimethoxyethane show that the effect of the substituent on the methine group of carboranes is transmitted predominantly by the induction mechanism.