Mononuclear N3S(thioether)-ligated copper(II) methoxide complexes: synthesis,characterization, and hydrolytic reactivity

Mononuclear copper(II) methoxide complexes supported by N(3)S(thioether) chelate ligands having two internal hydrogen bond donors have been prepared, comprehensively characterized, and evaluated for hydrolytic reactivity.     

Dioxygen activation by a neutral beta-diketiminato copper(I) ethylene complex

The synthesis and structure of two thermally stable neutral beta-diketiminato copper(I) olefin complexes are presented along with the structure of a Cu(II)2(mu-OH)2 dimer that results from the reaction of the Cu(I) ethylene complex with O2 via the proposed intermediacy of a Cu(III)2(mu-O)2 species.     

Copper(I) complex O(2)-reactivity with a N(3)S thioether ligand: a copper-dioxygen adduct including sulfur ligation, ligand oxygenation, and comparisons with all nitrogen ligand analogues

In order to contribute to an understanding of the effects of thioether sulfur ligation in copper-O(2) reactivity, the tetradentate ligands L(N3S) (2-ethylthio-N,N-bis(pyridin-2-yl)methylethanamine) and L(N3S')(2-ethylthio-N,N-bis(pyridin-2-yl)ethylethanamine) have been synthesized. Corresponding copper(I) complexes, [CuI(L(N3S))]ClO(4) (1-ClO(4)), [CuI(L(N3S))]B(C(6)F(5))(4) (1-B(C(6)F(5))(4)), and [CuI(L(N3S'))]ClO(4) (2), were generated, and their redox properties, CO binding, and O(2)-reactivity were compared to the situation with analogous compounds having all nitrogen donor ligands, [CuI(TMPA)(MeCN)](+) and [Cu(I)(PMAP)](+) (TMPA = tris(2-pyridylmethyl)amine; PMAP = bis[2-(2-pyridyl)ethyl]-(2-pyridyl)methylamine). X-ray structures of 1-B(C(6)F(5))(4), a dimer, and copper(II) complex [Cu(II)(L(N3S))(MeOH)](ClO(4))(2) (3) were obtained; the latter possesses axial thioether coordination. At low temperature in CH(2)Cl(2), acetone, or 2-methyltetrahydrofuran (MeTHF), 1 reacts with O(2) and generates an adduct formulated as an end-on peroxodicopper(II) complex [{Cu(II)(L(N3S))}(2)(mu-1,2-O(2)(2-))](2+) (4)){lambda(max) = 530 (epsilon approximately 9200 M(-1) cm(-1)) and 605 nm (epsilon approximately 11,800 M(-1) cm(-1))}; the number and relative intensity of LMCT UV-vis bands vary from those for [{Cu(II)(TMPA)}(2)(O(2)(2-))](2+) {lambda(max) = 524 nm (epsilon = 11,300 M(-1) cm(-1)) and 615 nm (epsilon = 5800 M(-1) cm(-1))} and are ascribed to electronic structure variation due to coordination geometry changes with the L(N3S) ligand. Resonance Raman spectroscopy confirms the end-on peroxo-formulation {nu(O-O) = 817 cm(-1) (16-18O(2) Delta = 46 cm(-1)) and nu(Cu-O) = 545 cm(-1) (16-18O(2) Delta = 26 cm(-1)); these values are lower in energy than those for [{Cu(II)(TMPA)}(2)(O(2)(2-))](2+) {nu(Cu-O) = 561 cm(-1) and nu(O-O) = 827 cm(-1)} and can be attributed to less electron density donation from the peroxide pi* orbitals to the Cu(II) ion. Complex 4 is the first copper-dioxygen adduct with thioether ligation; direct evidence comes from EXAFS spectroscopy {Cu K-edge; Cu-S = 2.4 Angstrom}. Following a [Cu(I)(L(N3S))](+)/O(2) reaction and warming, the L(N3S) thioether ligand is oxidized to the sulfoxide in a reaction modeling copper monooxygenase activity. By contrast, 2 is unreactive toward dioxygen probably due to its significantly increased Cu(II)/Cu(I) redox potential, an effect of ligand chelate ring size (in comparison to 1). Discussion of the relevance of the chemistry to copper enzyme O(2)-activation, and situations of biological stress involving methionine oxidation, is provided.     

Reaction of a copper(II)-nitrosyl complex with hydrogen peroxide: putative formation of a copper(I)-peroxynitrite intermediate

The reaction of a Cu(II)-nitrosyl complex (1) with hydrogen peroxide at -20 °C in acetonitrile results in the formation of the corresponding Cu(I)-peroxynitrite intermediate. The reduction of the Cu(II) center was monitored by UV-visible spectroscopic studies. Formation of the peroxynitrite intermediate has been confirmed by its characteristic phenol ring nitration reaction as well as isolation of corresponding Cu(I)-nitrate (2). On air oxidation, 2 resulted in the corresponding Cu(II)-nitrate (3). Thus, these results demonstrate a possible decomposition pathway for H(2)O(2) and NO through the formation of a peroxynitrite intermediate in biological systems.     

Studies on the complex formation of N,N-diethylglycine with copper(II) in acetonitrile

The formation of copper(II) complexes with N,N-diethylglycine in acetonitrile has been investigated by visible, infrared as well as NMR spectral techniques. It has been found that 11 and 12 complexes are formed. In both compounds nitrogen and carboxyl oxygen of ligand molecules are involved in coordination. The stability constants are reported.

---

Untersuchungen von Kupfer(II)-Komplexen mit N,N-Diethylglycin in Acetonitril

Zusammenfassung Die Bildung von Kupfer(II)-Komplexen mit N,N-Diethyglycin in Acetonitril wurde mit Hilfe von UV-VIS, IR- und NMR-Spektroskopie untersucht. Es wurde festgestellt, daß sich Komplexe der Zusammensetzung 11 und 12 bilden. In beiden Verbindungen koordinieren Stickstoff und Carboxylsauerstoff der Liganden. Die Stabilitätskonstanten wurden bestimmt.

     

Studies in the complex formation of metal ions with sugars. I. The complex formation of cobalt(II), cobalt(3), copper(II) and nickel(II) with mannitol

The use of elastic polyurethane foam as a support for chloranil was proved successful. Reductions of cerium(IV), vanadium(V) and iron(II) on foam-filled columns were carried out quantitatively and rapidly. The effect of flow-rate and temperature on the reduction of each metal ion was examined in detail. Cerium(IV) was reduced quantitatively on passing through the foam-redox column at flow-rates of 2–11 ml min^-1 at room temperature. The reduction of vanadium(V) and iron(III) was slower; complete reduction occurred only at flow-rates up to 4 and 2 ml min^-1 for V(V) and Fe(III), respectively. At 35°, however, it was possible to use flow-rates of 7 and 6 ml min^-1 for the quantitative reduction of V(V) and Fe(III), respectively.     

Copper(I) complexes, copper(I)/O(2) reactivity, and copper(II) complex adducts, with a series of tetradentate tripyridylalkylamine tripodal ligands

Copper(I) and copper(II) complexes possessing a series of related ligands with pyridyl-containing donors have been investigated. The ligands are tris(2-pyridylmethyl)amine (tmpa), bis[(2-pyridyl)methyl]-2-(2-pyridyl)ethylamine (pmea), bis[2-(2-pyridyl)ethyl]-(2-pyridyl)methylamine (pmap), and tris[2-(2-pyridyl)ethyl]amine (tepa). The crystal structures of the protonated ligand H(tepa)ClO(4), the copper(I) complexes [Cu(pmea)]PF(6) (1b-PF(6)), [Cu(pmap)]PF(6) (1c-PF(6)), and copper(II) complexes [Cu(pmea)Cl]ClO(4).H(2)O (2b-ClO(4).H(2)O), [Cu(pmap)Cl]ClO(4).H(2)O (2c-ClO(4).H(2)O), [Cu(pmap)Cl]ClO(4) (2c-ClO(4)), and [Cu(pmea)F](2)(PF(6))(2) (3b-PF(6)) were determined. Crystal data: H(tepa)ClO(4), formula C(21)H(25)ClN(4)O(4), triclinic space group P1, Z = 2, a = 10.386(2) A, b = 10.723(2) A, c = 11.663(2) A, alpha = 108.77(3) degrees, beta = 113.81(3) degrees, gamma = 90.39(3) degrees; 1b-PF(6), formula C(19)H(20)CuF(6)N(4)P, orthorhombic space group Pbca, Z = 8, a = 14.413(3) A, b = 16.043(3) A, c = 18.288(4) A, alpha = beta = gamma = 90 degrees; (1c-PF(6)), formula C(20)H(22)CuF(6)N(4)P, orthorhombic space group Pbca, Z = 8, a = 13.306(3) A, b = 16.936(3) A, c = 19.163(4) A, alpha = beta = gamma = 90 degrees; 2b-ClO(4).H(2)O, formula C(19)H(22)Cl(2)CuN(4)O(5), triclinic space group P1, Z = 4, a = 11.967(2) A, b = 12.445(3) A, c = 15.668(3) A, alpha = 84.65(3) degrees, beta = 68.57(3) degrees, gamma = 87.33(3) degrees; 2c-ClO(4).H(2)O, formula C(20)H(24)Cl(2)CuN(4)O(5), monoclinic space group P2(1)/c, Z = 4, a = 11.2927(5) A, b = 13.2389(4) A, c = 15.0939(8) A, alpha = gamma = 90 degrees, beta = 97.397(2) degrees; 2c-ClO(4), formula C(20)H(22)Cl(2)CuN(4)O(4), monoclinic space group P2(1)/c, Z = 4, a = 8.7682(4) A, b = 18.4968(10) A, c = 13.2575(8) A, alpha = gamma = 90 degrees, beta = 94.219(4) degrees; 3b-PF(6), formula [C(19)H(20)CuF(7)N(4)P](2), monoclinic space group P2(1)/n, Z = 2, a = 11.620(5) A, b = 12.752(5) A, c = 15.424(6) A, alpha = gamma = 90 degrees, beta = 109.56(3) degrees. The oxidation of the copper(I) complexes with dioxygen was studied. [Cu(tmpa)(CH(3)CN)](+) (1a) reacts with dioxygen to form a dinuclear peroxo complex that is stable at low temperatures. In contrast, only a very labile peroxo complex was observed spectroscopically when 1b was reacted with dioxygen at low temperatures using stopped-flow kinetic techniques. No dioxygen adduct was detected spectroscopically during the oxidation of 1c, and 1d was found to be unreactive toward dioxygen. Reaction of dioxygen with 1a-PF(6), 1b-PF(6), and 1c-PF(6) at ambient temperatures leads to fluoride-bridged dinuclear copper(II) complexes as products. All copper(II) complexes were characterized by UV-vis, EPR, and electrochemical measurements. The results manifest the dramatic effects of ligand variations and particularly chelate ring size on structure and reactivity.     

Structural diversity in a family of copper(I) thioether complexes

Copper(I) complexes of the tridentate thioether ligands [PhB(CH(2)SCH(3))(3)] (abbreviated PhTt), [PhB(CH(2)SPh)(3)] (PhTt(Ph)), [PhB(CH(2)S(t)()Bu)(3)] (PhTt(t)()(Bu)), and [PhB(CH(2)S(p)()Tol)(3)] (PhTt(p)()(Tol)) and bidentate thioether ligands [Ph(2)B(CH(2)SCH(3))(2)] (Ph(2)Bt), [Et(2)B(CH(2)SCH(3))(2)] (Et(2)Bt), and [Ph(2)B(CH(2)SPh)(2)] (Ph(2)Bt(Ph)) have been prepared and characterized. The solution and solid state structures are highly sensitive to the identity of the borato ligand employed. Ligands possessing the smaller (methylthio)methyl donors, [PhTt] and [Ph(2)Bt], yielded tetrameric species, [(PhTt)Cu](4) and [(Ph(2)Bt)Cu](4), containing both terminal and bridging thioether ligation. The ligands containing the larger (arylthio)methyl groups, [PhTt(Ph)] and [PhTt(p)()(Tol)], form monomeric [PhTt(Ar)]Cu(NCCH(3)) in solution and one-dimensional extended structures in the solid state. Each complex type reacted cleanly with acetonitrile, pyridine, or triphenylphosphine generating the corresponding four-coordinate monomer, of which [PhTt(Ph)]Cu(PPh(3)), [PhTt(p)()(Tol)]Cu(PPh(3)), and [Et(2)Bt]Cu(PPh(3))(2) have been structurally characterized.     

Geometric isomerism of copper(II) with monochlorobenzhydrazide chelate complexes

Summary Chelate complexes having a 12 Cu^II ion:(singly deprotonated ligand ratio, formed from Cu^II including 2-, 3- and 4-chlorobenzhydrazides, (ClC₆H₄C(O)NHNH₂) have been studied in the pH > 10 region. With the 2-chloro substituted derivative the cis-isomer is formed, whereas with the 3- and 4-chloro substituted derivatives trans-isomers are formed. The complexing schemes are described.     

Novel thiosalamo ligand as a remarkably stable N2S2 salen-type chelate and synthesis of a nickel(II) complex

Novel N2S2 tetradentate chelate ligand H2tsalamo, which contains both thiol groups and C=N moieties, was synthesized as a remarkably stable compound. Complexation between H2tsalamo and nickel(II) acetate gave a square planar complex [Ni(tsalamo)] as dark brown crystals, whose structure was determined by X-ray crystallography. In contrast, the corresponding N2O2 ligands, salamo and 3-MeOsalamo, gave trinuclear and mononuclear complexes, respectively, in which all the nickel atoms have octahedral geometry.     

Preparation and crystal structure of a copper(II) homobinuclear chelate

Summary The structure of the homobinuclear complex Cu₂(aapen)H₂O, where aapen is the tetraanionic ligand derived from the condensation of 1,2-diaminocthane witho-acetoacetylphenol, has been determined from diffractometer data and refined to R = 6.1%. The crystals are monoclinic,P2₁/c, witha = 12.991(5),b = 8.530(4),c = 18.546(6) Å, and = 104.10(4)°; Z = 4. The ligand employed has two different coordination sets of atoms, N₂O₂ and O₂O₂, two oxygen atoms being common to both donor sets. In the complex, one copper atom is retained in the plane of the inner N₂O₂ chamber whilst the other, which is incorporated in the outer O₂O₂ chamber, is five-coordinate, being axially bonded to a water molecule.     

A four-membered chelate complex of Cu(II) with creatinine

The complex formation between Cu(II) and creatinine was studied by means of electronic, IR and EPR spectroscopy. The spectral data show the formation of a Cu(II) four-membered chelate with distorted rhombic structure.