A convenient synthesis of copper(I) carboxylates

A simple procedure is described for the synthesis of aliphatic and aromatic copper(I) carboxylates by the reduction of copper(II) carboxylates with commercially available tin(II) 2-ethylhexanoate. In this way copper(I) acetate, benzoate and stearate have been prepared in good yield and purity from the corresponding copper(II) carboxylates.     

Darstellung und Fluoreszenzeigenschaften von Kupfer(I)-Carboxylaten

Preparation and Fluorescence Properties of Copper (I) Carboxylates By reduction of copper(II) carboxylates with ascorbic acid in aqueous solutions some aromatic copper(I) compounds can easily be obtained by precipitation. Powder x-ray photographs of copper(I) propionate and copper(I) monochloroacetate have similar characteristic interferences as copper(I) acetate, from which a layer structure is known. All the here described copper(I) carboxylates are fluorescent, indicating that oxygen atoms behave as sufficently strong donors, but most of them and especially those with tetragonal structure, do not change their fluorescence colour by cooling in liquid nitrogen like many copper(I) complexes with nitrogen bases do (fluorescence thermochromism). Fluorescence thermochromism occurs however at copper(I) 3-hydroxybenzoate. This presumably results from a lower symmetry.     

Synthesis of Enol Esters from Copper(I) Carboxylates Generated from Copper(I) Trifluoromethanesulfonate Benzene Complex

A rapid method for the preparation of copper(I) carboxylates by use of copper(I) trifluoromethanesulfonate benzene complex followed by their conversion to enol esters under mild conditions is presented.     

Decarboxylation oxydante des acides carboxyliques aliphatiques par un systeme cuivre(i)/oxygene.

A new oxidative decarboxylation reaction converts carboxylic acids 1 or 2 (Z = OH) to the corresponding carbonyl compounds 3, in the presence of oxygen and catalytic amounts of copper(I)probably via transient copper(III) carboxylates.     

Über Kupfer(I)-carboxylate und Chlorocuprate(I)

In mixtures of 7 vol. acetonitrile and 3 vol. acetic acid, solutions or suspensions of copper(II) acetate can be reduced with hydrazine hydrate to solutions of copper(I) acetate. In this way, purely white copper(I) acetate can be isolated. Other copper(I) carboxylates can be prepared by reduction of copper(II) carboxylates or by reaction of solid carboxylic acids with copper(I) acetate. By adding acetyl chloride to solutions of copper(I) acetate in acetonitrile/acetic acid mixtures, solutions of chlorocuprates(I) are formed. From these, highly pure copper(I) chloride can be obtained. By adding alkali acetate or tetramethyl ammonium chloride to solutions of chlorocuprates(I), the pure compounds Cs₃[Cu₂Cl₅], Rb₂[CuCl₃] and NMe₄[Cu₂Cl₃] were obtained.     

Cu(I)-catalyzed regioselective synthesis of polysubstituted furans from propargylic esters via postulated (2-furyl)carbene complexes

Polysubstituted furan derivatives are regioselective obtained from (bis-alkynyl)methyl carboxylates in the presence of catalytic amounts of copper(I) salts. This multistep process is consistent with the intermediacy of a copper(I) (2-furyl)carbene complex which is intercepted by suitable trapping reagents.     

The first hexanuclear copper(I) carboxylate: X-ray crystal structure and reactivity in solution and gas-phase reactions

The carboxylate ligand-exchange reaction of copper(I) trifluoroacetate by 3,5-difluorobenzoate yielded a new product, [Cu(O2C(3,5-F)2C6H3)] (1). Single crystals of 1 suitable for X-ray structural characterization were obtained by sublimation-deposition procedures at 230 degrees C. An X-ray diffraction study revealed a remarkable planar hexanuclear copper(I) core supported by bridging carboxylates, the first such structural type among other known copper(I) carboxylates. The Cu...Cu distances within the core range from 2.7064(8) to 2.8259(8) A and fall into the category of cuprophillic interactions. The hexacopper unit remains intact upon gas-phase deposition with a planar polyarene, coronene (C24H12), to give [Cu6(O2C(3,5-F)2C6H3)6](C24H12) (2). Density functional theory calculations suggest the latter compound to be a cocrystallization product having electrostatic interactions between the hexacopper complex and coronene. However, cocrystallization affects the photophysical properties of 2. While copper(I) 3,5-difluorobenzoate (1) exhibits photoluminescence at ca. 554 nm (lambda(ex) = 350 nm) in the solid state, compound 2 is nonluminescent at room temperature in the visible region. Gas-phase and solution reactions of 1 with alkyne ligands, diphenylacetylene (C14H10) and 1,4-bis(p-tolylethynyl)benzene (C24H18), result in the rupture of the [Cu6] core to afford dinuclear organometallic copper(I) complexes. The latter have a dimetal core cis-bridged by two carboxylate groups with acetylene ligands eta(2)-coordinated to each copper(I) center.     

Enantioselective Borylative Dearomatization of Indoles through Copper(I) Catalysis

The enantioselective borylative dearomatization of a heteroaromatic compound has been achieved using a copper(I) catalyst and a diboron reagent. This reaction involves the regio‐ and enantioselective addition of active borylcopper(I) species to indole‐2‐carboxylates, followed by the diastereoselective protonation of the resulting copper(I) enolate to give the corresponding chiral indolines, which bear consecutive stereogenic centers.     

Preparation of Complexes of Copper (II) Aryl Carboxylates with Morpholine

Complexes of copper (II) aryl carboxylates with morpholine were prepared by the interaction of the copper carboxylate with the morpholine equimolar as well as in large excess quantities in acetone medium. The complexes isolated correspond to 1:1 and 1:2 stoichiometry. In continuation of our work on the preparation of complexes of copper (II) aryl carboxylates with nitrogen donors like aliphatic amines,¹⁾ heterocyclic amines²⁾ and pyridine–N–Oxide³⁾, the present communication deals with the preparation of complexes of copper (II) aryl carboxylates with morpholine.     

Tetranuclear copper(I) carboxylates: the effect of a stepwise increase in Lewis acidity on solid-state structures and photoluminescence

X-Ray diffraction studies of three aliphatic copper(I) carboxylates revealed a tetranuclear core structure for [Cu(4)(O(2)CCH(2)CH(3))(4)] (1), [Cu(4)(O(2)CCF(3))(O(2)CCH(2)CH(3))(3)] (2), and [Cu(4)(O(2)CCF(2)CF(3))(4)] (3). The effect of a stepwise increase in electrophilicity on solid-state interactions of copper(I) tetramers as well as the implications of structural variations on photoluminescent properties of the above copper(I) propionates have been discussed.     

Preparation of Complexes of Copper(II) Aryl Carboxylates with Diethyl Amine and Dipropyl Amine

Copper aryl carboxylates are known to form co-ordination complexes with various nitrogen donors^1-4). Except copper (II) benzoate⁵⁾ complexes of other copper (II) aryl carboxylates with secondary amines such as diethyl amine and dipropyl amine are not known. The present communication deals with the preparation of complexes of various copper (II) aryl carboxylates with diethyl amine and dipropyl amine.     

Imidazol(in)ium‐2‐Carboxylates as Efficient Precursors to N‐Heterocyclic Carbene Complexes of Copper and Silver

Copper and silver N‐heterocyclic carbene (NHC) complexes were prepared through a simple, base‐free protocol involving the decomposition of corresponding imidazol(in)ium‐2‐carboxylates under thermolytic conditions and a subsequent reaction of the in situ generated carbenes with copper(I) or silver(I) chloride, respectively. The desired NHC metal complexes were isolated with good yields after simple crystallization.     

Complexes of Copper (II) Aryl Carboxylates with 2, 6-Lutidine

Copper (II) aryl carboxylates are known to form co-ordination complexes with various oxygen and nitrogen donors such as pyridine-N-oxide¹⁾, quinoline and isoquinoline²⁾ diethylamine and dipropylamine¹⁾. There is no reference in literature regarding the preparation of complexes of copper (II) aryl carboxylates with 2,6-lutidine. The present communication describes the preparation of complexes of various copper (II) aryl carboxylates with 2,6-lutidine in acetone or ethylacetate medium.     

Electrochemical synthesis of copper(II) carboxylates

A number of copper(II) carboxylates have been synthesized by anodic oxidation of copper. The reactions were found to proceed with current efficiencies of 0.95 to 1.00 eq./Faraday. Reaction products have been characterized by infrared spectral studies and analysis of copper.     

Chromatographic determination of copper speciation in jet fuel

A method is described that allows one to distinguish and quantitate two different classes of copper compounds in the same hydrocarbon sample. This will enable the study of the effects of different copper compounds on the performance and stability of petroleum samples. Copper N,N'-disalicylidene-1,2-propylenediamine (CuDMD) and several copper carboxylates were preconcentrated from a hydrocarbon matrix using a column packed with polyvinylpyrrolidone, (C(6)H(9)NO)(x), a novel polymeric stationary phase. The copper complexes were then sequentially eluted using a step gradient program beginning with hexane/isopropyl alcohol as the eluent and ending with an acetic acid/isopropyl alcohol eluent. The copper complexes were detected by serial UV absorbance and flame atomic absorbance (FAA) detection. With on-column preconcentration and FAA detection, the limits of detection were 7 and 40 ppb copper for CuDMD and the copper carboxylates respectively. With this method, it was possible to distinguish between the two different classes of copper compounds in the same hydrocarbon sample, which will help to provide an understanding of the catalytic activity of different copper compounds, leading to a better understanding of the factors causing fuel instability. The method promises to be a valuable tool in the analysis and characterization of copper compounds in petroleum samples.     

Synthesis, crystal structure and thermal decomposition of a new copper propionate [Cu(CH3CH2COO)2]·2H2O

A new copper propionate complex was synthesised and characterized for application as precursor for CuO based oxide thin films deposition. The FT-IR and X-ray diffraction analyses have revealed the formation of a cooper propionate complex [Cu(CH₃CH₂COO)₂]·2H₂O. The crystal and molecular structure of a new copper propionate complex was determined by XRD on the copper propionate single crystal. The copper propionate complex has a binuclear structure, connected by bridging bidentate carboxylates groups and a Cu?Cu bond of 2.6 Å. The thermal decomposition of copper propionate has been investigated by thermal analysis using thermogravimetric (TG) and differential thermal analysis (DTA), differential thermal analysis coupled with quadrupole mass spectrometry-QMS, X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR) techniques. TG and XRD data indicate the reduction of Cu(II)-Cu(I,0) during the decomposition of copper propionate.     

Catalytic asymmetric synthesis of nitrocyclopropane carboxylates

A Cu(I)-catalyzed asymmetric cyclopropanation of alkenes with an iodonium ylide has been developed. The copper source, hypervalent iodine source, solvent, and additives all have a significant effect on the yields and enantioselectivities. High enantioselectivity (up to 99:1 er) and diastereoselectivity (95:5 dr trans/cis) were achieved for a wide range of alkenes. Conditions were developed to convert the trans products to the cis isomers. In addition, 1-nitrocyclopropyl carboxylates were transformed into the corresponding substituted cyclopropane amino acids and aminocyclopropanes. Moreover, a comparative study between Zn- and In-mediated reduction reactions of the nitro group in these compounds with regards to the er erosion in the process is also documented.     

A nanoporous metal-organic framework with accessible Cu2+ sites for the catalytic Henry reaction

A novel 3D porous metal-organic framework containing 1D nanoscale opening channels was constructed from two kinds of pyridine carboxylates and copper(II) nodes with reachable copper sites located in the channel walls, which can be subsequently used to prompt the Henry reaction of benzaldehydes and nitroalkanes with remarkable catalytic activity compared with homogeneous copper cations.     

Biaryl synthesis via Pd-catalyzed decarboxylative coupling of aromatic carboxylates with aryl halides

A new strategy for the regiospecific construction of unsymmetrical biaryls is presented, in which easily available salts of carboxylic acids are decarboxylated in situ to give arylmetal species that serve as the nucleophilic component in a catalytic cross-coupling reaction with aryl halides. The catalyst system consists of a copper phenanthroline complex that mediates the extrusion of CO2 from aromatic carboxylates to generate arylcopper species, and a palladium complex that catalyzes the cross-coupling of these intermediates with aryl halides. This bimetallic system allows the direct coupling of various aryl, heteroaryl, or vinyl carboxylic acids with aryl or heteroaryl iodides, bromides, or chlorides at 160 degrees C in the presence of a mild base such as potassium carbonate. The present scope and potential economic impact of the reaction are demonstrated by the synthesis of 42 biaryls, some of which are of substantial industrial relevance. Remaining challenges and future perspectives of the new transformation are discussed.     

Syntheses and crystal structures of "unligated" copper(I) and copper(II) trifluoroacetates

Two extremely unstable copper trifluoroacetates with no exogenous ligands, namely, Cu(O2CCF3) (1) and Cu(O2CCF3)2 (2), are prepared for the first time and obtained in crystalline form by deposition from the vapor phase. Their structures are determined by X-ray crystallography. The crystallographic parameters are as follows: for 1, monoclinic space group P2(1)/c, with a = 9.7937(6) A, b = 15.322(1) A, c = 12.002(1) A, beta = 106.493(9) degrees, and Z = 4; for 2, orthorhombic space group Pcca, with a = 16.911(1) A, b = 10.5063(9) A, c = 9.0357(6) A, and Z = 4. Both structures are unique among other CuI and CuII carboxylates, as well as among metal carboxylates in general. Compound 1 consists of a planar rhombus of four copper atoms with sides of 2.719(1)-2.833(1) A and trifluoroacetate ligands bridging the pairs of adjacent metal atoms alternately above and below the plane. The tetrameric units are further aggregated in a polymeric zigzag ribbon [Cu4(O2CCF3)4]infinity by virtue of intermolecular Cu...O contacts. The structure of 2 is built on cis bis-bridged dimers in which every metal atom is also connected with two copper atoms of the neighboring units. The stacking planes in this extended chain are almost perpendicular to one another. The Cu...Cu distance inside the dimer is 3.086(2) A, indicating a nonbonding interaction.