Synthesis,characterization and crystal structures of the bidentate Schiff base N,N′‐bis(2‐nitrocinnamaldehyde)ethylenediamine and its complex with CuNCS and triphenylphosphane

Reaction of copper(I) thiocyanate and triphenylphosphane with the bidentate Schiff base N,N′‐bis(trans‐2‐nitrocinnamaldehyde)ethylenediamine {Nca₂en, (1); systematic name (1E,1′E,2E,2′E)‐N,N′‐(ethane‐1,2‐diyl)bis[3‐(2‐nitrophenyl)prop‐2‐en‐1‐imine]}, C₂₀H₁₈N₄O₄, in a 1:1:1 molar ratio in acetonitrile resulted in the formation of the complex {(1E,1′E,2E,2′E)‐N,N′‐(ethane‐1,2‐diyl)bis[3‐(2‐nitrophenyl)prop‐2‐en‐1‐imine]‐κ²N,N′}(thiocyanato‐κN)(triphenylphosphane‐κP)copper(I)], [Cu(NCS)(C₂₀H₁₈N₄O₄)(C₁₈H₁₅P)] or [Cu(NCS)(Nca₂en)(PPh₃)], (2). The Schiff base and copper(I) complex have been characterized by elemental analyses, IR, electronic and ¹H NMR spectroscopy, and X‐ray crystallography [from synchrotron data for (1)]. The molecule of (1) lies on a crystallographic inversion centre, with a trans conformation for the ethylenediamine unit, and displays significant twists from coplanarity of its nitro group, aromatic ring, conjugated chain and especially ethylenediamine segments. It acts as a bidentate ligand coordinating via the imine N atoms to the Cu^I atom in complex (2), in which the ethylenediamine unit necessarily adopts a somewhat flattened gauche conformation, resulting in a rather bowed shape overall for the ligand. The NCS⁻ ligand is coordinated through its N atom. The geometry around the Cu^I atom is distorted tetrahedral, with a small N—Cu—N bite angle of 81.56 (12)° and an enlarged opposite angle of 117.29 (9)° for SCN—Cu—P. Comparisons are made with the analogous Schiff base having no nitro substituents and with metal complexes of both ligands.     

The crystal and molecular structures of three copper‐containing complexes and their activities in mimicking galactose oxidase

The structures of three copper‐containing complexes, namely (benzoato‐κ²O,O′)[(E)‐2‐({[2‐(diethylamino)ethyl]imino}methyl)phenolato‐κ³N,N′,O]copper(II) dihydrate, [Cu(C₇H₅O₂)(C₁₃H₁₉N₂O)]·2H₂O, 1 , [(E)‐2‐({[2‐(diethylamino)ethyl]imino}methyl)phenolato‐κ³N,N′,O](2‐phenylacetato‐κ²O,O′)copper(II), [Cu(C₈H₇O₂)(C₁₃H₁₉N₂O)], 2 , and bis[μ‐(E)‐2‐({[3‐(diethylamino)propyl]imino}methyl)phenolato]‐κ⁴N,N′,O:O;κ⁴O:N,N′,O‐(μ‐2‐methylbenzoato‐κ²O:O′)copper(II) perchlorate, [Cu₂(C₈H₇O₂)(C₁₂H₁₇N₂O)₂]ClO₄, 3 , have been reported and all have been tested for their activity in the oxidation of d ‐galactose. The results suggest that, unlike the enzyme galactose oxidase, due to the precipitation of Cu₂O, this reaction is not catalytic as would have been expected. The structures of 1 and 2 are monomeric, while 3 consists of a dimeric cation and a perchlorate anion [which is disordered over two orientations, with occupancies of 0.64 (4) and 0.36 (4)]. In all three structures, the central Cu atom is five‐coordinated in a distorted square‐pyramidal arrangment (τ parameter of 0.0932 for 1 , 0.0888 for 2 , and 0.142 and 0.248 for the two Cu centers in 3 ). In each species, the environment about the Cu atom is such that the vacant sixth position is open, with very little steric crowding.     

Dimeric copper(II) trimethylsilyl­acetate adducts with pyridine, 2‐­methylpyridine, 3‐methylpyridine and quinoline,and a polymeric copper(II) trimethylsilylacetate

In the crystals of bis(pyridine‐N)tetrakis(μ‐trimethylsilylacetato‐O:O′)dicopper(II), [Cu₂(C₅H₁₁O₂Si)₄(C₅H₅N)₂], (I), the dinuclear Cu^II complexes have cage structures with Cu?Cu distances of 2.632 (1) and 2.635 (1) Å. In the crystals of bis(2‐­methylpyridine‐N)tetrakis(μ‐trimethylsilylacetato‐O:O′)dicopper(II), [Cu₂(C₅H₁₁O₂Si)₄(C₆H₇N)₂], (II), bis­(3‐methylpyridine‐N)tetrakis(μ‐trimethylsilylacetato‐O:O′)dicopper(II), [Cu₂(C₅H₁₁O₂Si)₄(C₆H₇N)₂], (III), and bis(quinoline‐N)­tetrakis(μ‐­trimethylsilylacetato‐O:O′)dicopper(II), [Cu₂(C₅H₁₁O₂Si)₄(C₉H₇N)₂], (IV), the centrosymmetric dinuclear Cu^II complexes have a cage structure with Cu?Cu distances of 2.664 (1), 2.638 (3) and 2.665 (1) Å, respectively. In the crystals of catena‐poly­[tetrakis(μ‐trimethylsilylacetato‐O:O′)dicopper(II)], [Cu₂(C₅H₁₁O₂Si)₄]_n, (V), the dinuclear Cu^II units of a cage structure are linked by the cyclic Cu—O bonds at the apical positions to form a linear chain by use of a glide translation.     

Study on kinetics and mechanism of copper-catalyzed oxidation of hydrazine by iron (III) in acid solution

The copper-catalyzed oxidation of hydrazine by iron(III) in acid solution follows the rate law -d[Fe(III)]/dt = kK_h[Cu(II)]²/(K_h + [H⁺]), where K_h is the hydrolysis constant of Cu²⁺, k was found to be 8.8±0.8, 13.2±1.4 and 17.5±1.3 min^?1 at 35, 40, and 45°C respectively and μ= 0.2 mol/L. The composition of the activated complex is Cu²⁺, CuOH⁺, N₂H₄, H⁺ or others. Perhaps several hydrazine complexes of Cu(II) participate in the reaction and one of them isolated was Cu(N₂H₄)₂(HSO₄)₂. Study on the oxidation of this complex is also in conformity with the above rate law.     

Synthesis, characterization and electrochemical investigation of a novel vic-dioxime ligand and its some transition metal complexes

4-(Chloroacetyl)diphenyl ether was synthesized from chloroacetyl chloride and diphenyl ether in the presence of AlCl₃ as catalyst in a Friedel-Crafts reaction. Then, its keto oxime and dioxime derivatives were prepared. 4-phenoxy-(N-4-chlorophenylamino)phenylglyoxime (H₂L) was synthesized from 4-(phenoxy)chlorophenylglyoxime and 4-chloroaniline. Ni(II), Co(II) and Cu(II) complexes of H₂L were obtained. The mononuclear Ni(II), Co(II) and Cu(II) complexes of H₂L have a metal–ligand ratio of 1:2 and the ligand coordinates through the two N atoms, as do most of the vic-dioximes. The structure of the ligand was identified by FT-IR, ¹H NMR, ¹³C NMR, ¹³C NMR (APT) spectroscopy and elemental analysis data. The structures of the complexes were characterized on the basis of FT-IR, ICP-AES, UV-Vis, elemental analysis, magnetic susceptibility measurements, and cyclic voltammetry. The electrochemical measurements were obtained by using cyclic voltammetry in DMF solution at room temperature. The electrochemical behaviors of H₂L and its complexes showed that the redox process of H₂L has one irreversible oxidation wave, whereas the redox processes of the complexes have both oxidation and reduction waves with metal centered.     

Negatively Charged Metallacarborane Redox Couples with Both Members Stable to Air

The metallacarborane [3,3′‐Co(1,2‐closo‐C₂B₉H₁₁)₂]^? has been synthesized. This species allows the formation of redox couples in which both partners are negatively charged. The E_1/2 potential can be tuned by adjusting the nature and number of substituents on B and C. The octaiodinated species [3,3′‐Co(1,2‐closo‐C₂B₉H₇I₄)₂]^? is the most favorable, as it is isolatable and stable in air. A DFT study on stability and redox potentials of complexes has been performed.     

Structural studies of (prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine hetero‐scorpionate copper complexes

The structures of five compounds consisting of (prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine complexed with copper in both the Cu^I and Cu^II oxidation states are presented, namely chlorido{(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(I) 0.18‐hydrate, [CuCl(C₁₅H₁₇N₃)]·0.18H₂O, (1), catena‐poly[[copper(I)‐μ₂‐(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ⁵N,N′,N′′:C²,C³] perchlorate acetonitrile monosolvate], {[Cu(C₁₅H₁₇N₃)]ClO₄·CH₃CN}_n, (2), dichlorido{(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(II) dichloromethane monosolvate, [CuCl₂(C₁₅H₁₇N₃)]·CH₂Cl₂, (3), chlorido{(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(II) perchlorate, [CuCl(C₁₅H₁₇N₃)]ClO₄, (4), and di‐μ‐chlorido‐bis({(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(II)) bis(tetraphenylborate), [Cu₂Cl₂(C₁₅H₁₇N₃)₂][(C₆H₅)₄B]₂, (5). Systematic variation of the anion from a coordinating chloride to a noncoordinating perchlorate for two Cu^I complexes results in either a discrete molecular species, as in (1), or a one‐dimensional chain structure, as in (2). In complex (1), there are two crystallographically independent molecules in the asymmetric unit. Complex (2) consists of the Cu^I atom coordinated by the amine and pyridyl N atoms of one ligand and by the vinyl moiety of another unit related by the crystallographic screw axis, yielding a one‐dimensional chain parallel to the crystallographic b axis. Three complexes with Cu^II show that varying the anion composition from two chlorides, to a chloride and a perchlorate to a chloride and a tetraphenylborate results in discrete molecular species, as in (3) and (4), or a bridged bis‐μ‐chlorido complex, as in (5). Complex (3) shows two strongly bound Cl atoms, while complex (4) has one strongly bound Cl atom and a weaker coordination by one perchlorate O atom. The large noncoordinating tetraphenylborate anion in complex (5) results in the core‐bridged Cu₂Cl₂ moiety.     

Oxidation of electron deficient olefins using a copper(II) complex based on a bis-benzimidazole diamide ligand

New bis-benzimidazole based diamide ligands N, N′-bis(2-methyl benzimidazolyl)-benzene-1,3-dicarboxamide [GBBA] and N-Octyl-N, N′-bis(2-methyl benzimidazolyl)-benzene- 1,3-dicarboxamide [O-GBBA] have been synthesized and utilized to prepare Cu(II) complexes of general composition [Cu(GBBA)X ₂] · nH₂O and [Cu(O-GBBA)X₂] · n H₂O, where X is an exogenous anionic ligand (X = Cl⁻, NO₃⁻, SCN⁻). The oxidation of electron deficient olefins has been investigated using [Cu(O-GBBA)X₂] · nH₂O as catalyst and TBHP as an alternate source of oxygen. The respective ketonic products have been isolated and characterized by ¹H-NMR. The complex [Cu(GBBA)(NO₃)₂] · 4H₂O has been characterized structurally. It crystallizes in a monoclinic space group C2/c. Low temperature EPR spectra have been obtained for the complexes that shows g_II > g_I > 2.0024, indicating a tetragonal geometry in the solution state. The complexes display a quasi reversible redox wave due to the Cu(II)/Cu(I) reduction process. The E_1/2 values shift anodically as NO₃⁻ < SCN⁻ < Cl⁻.     

The first square‐planar copper(II) 1:2 complex with differently coordinated 2‐hydroxybenzaldehyde 4‐allylthiosemicarbazone ligands

The title compound, [(Z)‐4‐allyl‐2‐(2‐hydroxybenzylidene)thiosemicarbazide‐κS][(E)‐4‐allyl‐1‐(2‐oxidobenzylidene)thiosemicarbazidato‐κ³O,N¹,S]copper(II) monohydrate, [Cu(C₁₁H₁₁N₃OS)(C₁₁H₁₃N₃OS)]·H₂O, crystallized as a rotational twin in the monoclinic crystal system (space group Cc) with two formula unit (Z′ = 2) in the asymmetric unit, one of which contains an allyl substituent disordered over two positions. The Cu^II atom exhibits a distorted square‐planar geometry involving two differently coordinated thiosemicarbazone ligands. One ligand is bonded to the Cu^II atom in a tridentate manner via the phenolate O, azomethine N and thioamide S atoms, while the other coordinates in a monodentate manner via the S atom only. The complex is stabilized by an intramolecular hydrogen bond, which creates a six‐membered pseudo‐chelate metalla‐ring. The structure analysis indicates the presence of the E isomer for the tridentate ligand and the Z isomer for the monodentate ligand. The crystal structure contains a three‐dimensional network built from intermolecular O—H...O, N—H...O, O—H...N and N—H...S hydrogen bonds.     

Bis{1‐n‐hex­yl‐3‐meth­yl‐4‐[1‐(phenyl­imino)prop­yl]‐1H‐pyrazol‐5‐olato}­copper(II): a new copper(II) complex with a chelating alkyl­pyrazolone‐based enamine

The title compound, [Cu(C₁₉H₂₆N₃O)₂], is the first reported complex of the alkyl­pyrazolone‐derived ligand 1‐n‐hexyl‐3‐methyl‐4‐[1‐(phenylimino)propyl]‐1H‐pyrazol‐5(4H)‐one. The most notable feature is the imine–enol character presented by the ligand due to coordination, in spite of its enamine–ketone structure in the free state. The ligand chelates through N and O atoms, resulting in a square‐planar coordination around the Cu^II atom, which lies on an inversion centre.     

(2‐Aminopyrimidine‐κN1)aqua(pyridine‐2,6‐dicarboxylato‐κ3O2,N,O6)copper(II): X‐ray and DFT calculated structure

In the title compound, [Cu(C₇H₃N₂O₄)(C₄H₅N₂)(H₂O)], (I), pyridine‐2,6‐dicarboxylate (pydc²⁻), 2‐aminopyrimidine and aqua ligands coordinate the Cu^II centre through two N atoms, two carboxylate O atoms and one water O atom, respectively, to give a nominally distorted square‐pyramidal coordination geometry, a common arrangement for copper complexes containing the pydc²⁻ ligand. Because of the presence of Cu...X_bridged contacts (X = N or O) between adjacent molecules in the crystal structures of (I) and three analogous previously reported compounds, and the corresponding uncertainty about the effective coordination number of the Cu^II centre, density functional theory (DFT) calculations were used to elucidate the degree of covalency in these contacts. The calculated Wiberg and Mayer bond‐order indices reveal that the Cu...O contact can be considered as a coordination bond, whereas the amine group forming a Cu...N contact is not an effective participant in the coordination environment.     

Mono‐ and dinuclear CuII complexes of the benzyldipicolylamine (BDPA) ligand: crystal structure,synthesis and characterization

The crystal structures of mono‐ and dinuclear Cu^II trifluoromethanesulfonate (triflate) complexes with benzyldipicolylamine (BDPA) are described. From equimolar amounts of Cu(triflate)₂ and BDPA, a water‐bound Cu^II mononuclear complex, aqua(benzyldipicolylamine‐κ³N ,N′ ,N ′′)bis(trifluoromethanesulfonato‐κO )copper(II) tetrahydrofuran monosolvate, [Cu(CF₃SO₃)₂(C₁₉H₁₉N₃)(H₂O)]·C₄H₈O, (I), and a triflate‐bridged Cu^II dinuclear complex, bis(μ‐trifluoromethanesulfonato‐κ²O :O ′)bis[(benzyldipicolylamine‐κ³N ,N′ ,N ′′)(trifluoromethanesulfonato‐κO )copper(II)], [Cu₂(CF₃SO₃)₄(C₁₉H₁₉N₃)₂], were synthesized. The presence of residual moisture in the reaction medium afforded water‐bound complex (I), whereas dinuclear complex (II) was synthesized from an anhydrous reaction medium. Single‐crystal X‐ray structure analysis reveals that the Cu^II centres adopt slightly distorted octahedral geometries in both complexes. The metal‐bound water molecule in (I) is involved in intermolecular O—H…O hydrogen bonds with triflate ligands and tetrahydrofuran solvent molecules. In (II), weak intermolecular C—H…F(triflate) and C—H…O(triflate) hydrogen bonds stabilize the crystal lattice. Complexes (I) and (II) were also characterized fully using FT–IR and UV–Vis spectroscopy, cyclic voltammetry and elemental analysis.     

The chemistry of pyridine thiols and related ligands, Part 5. Synthesis and spectroscopy of nickel(II) and copper(II) complexes containing 1-oxopyridine-2-thione and 2,2′-bipyridine or 1,10-phenanthroline

Summary Reactions of bis(1-oxopyridine-2-thione) Ni^II or Cu^II with 2,2-bipyridine (bipy) or 1,10-phenanthroline (phen) yield complexes of stoichiometry: Ni(C₅H₄NOS)₂L {L = bipy, two isomers: (1) and (2), L = phen, one isomer (3)} and Cu(C₅H₄NOS)₂(phen)·0.75CHCl₃ (4). The spectroscopy (i.r., u.v.-vis., e.s.r.) and magnetism studies of the above complexes are described. On the basis of conductivity, the Cu^II-phen complex has been formulated as [Cu(C₅H₄NOS)(phen)₂][Cu(C₅H₄NOS)₃]·1.5CHCl₃ (4). The vis. absorption spectra support similar octahedral structures for the minor bipy isomer (2) and for the Ni^II-phen complex [(3)], whereas the major isomer [(1)] has a different structure. The e.s.r. spectrum of the Cu^II-phen complex (4) is commensurate with an elongated octahedral structure. New methods for the preparation and spectroscopy of M(C₅H₄NOS)₂ (M = Mn, Ni, Cu or Zn) compounds have been investigated.     

New unsymmetrical μ-phenoxo bridged binuclear copper(II) complexes

A series of binuclear Cu^II complexes [Cu₂XL] ⁿ⁺ having two copper(II) ions bridged by different motifs (X = OH^–, MeCO₂ ^–, or Cl^–) have been prepared using the ligands: H₂L¹ = 4-methyl-2-[N-(2-{dimethylamino}ethyl-N-methyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol, H₂L² = 4-nitro-2-[N-(2-{dimethylamino}ethyl-N-methyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol, H₂L³ = 4-methyl-2-[N-(2-{diethylamino}ethyl-N-ethyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol and H₂L⁴ = 4-nitro-2-[N-(2-{diethylamino}ethyl-N-ethyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol. The complexes have been characterized by spectroscopic, analytical, magnetic and electrochemical measurements. Cryomagnetic investigations (80–300 K) revealed anti-ferromagnetic exchange between the Cu^II ions (–2J in the range –50 to –182 cm^–1). The strength of anti-ferromagnetic coupling lies in the order: OAc > OH > Cl. Cyclic voltammetry revealed the presence of two redox couples, assigned to Cu^II/Cu^II/Cu^II/Cu^I/Cu^I/Cu^I. The first reduction potential is sensitive to electronic effects from the aromatic ring substituents and steric effect on the donor nitrogens (side arm) of the ligand systems.     

Synthesis,spectral characterization,electrochemistry and catalytic activities of Cu(II) complexes of bifunctional tridentate Schiff bases containing O?N?O donors

Paramagnetic copper(II) complexes of the type [Cu(PPh₃)(L)] (where L = bifunctional tridentate Schiff bases) were synthesized from the reaction of anthranillic acid with salicylaldehyde (H₂L¹), 2‐hydroxy‐1‐naphthaldehyde (H₂L²), o‐hydroxyacetophenone (H₂L³) and o‐vanillin (H₂L⁴) with monomeric metal precursor [CuCl₂(PPh₃)₂]. The obtained complexes were characterized by elemental analysis, magnetic susceptility and spectroscopic methods (FT‐IR, UV–vis and EPR and cyclic voltammetry). EPR and redox potential studies have been carried out to elucidate the electronic structure, nature of metal–ligand bonding and electrochemical features. EPR spectra exhibit a four line pattern with nitrogen super‐hyperfine couplings originating from imine nitrogen atom. These planar complexes possess a significant amount of tetrahedral distortion leading to a pseudo‐square planar geometry, as is evidenced from EPR properties. Cyclic voltammograms of all the complexes display quasireversible oxidations, Cu(III)? Cu(II), in the range 0.31–0.45 V and reduction peaks, Cu(II)? Cu(I),in the range ?0.29 to ?0.36 V, involving a large geometrical change and irreversible. The observed redox potentials vary with respect to the size of the chelate ring of the Schiff base ligands. Further, the catalytic activity of all the complexes has been found to be high towards the oxidation of alcohols into aldehydes and ketones in the presence of N‐methylmorpholine‐N‐oxide as co‐oxidant. The formation of high valent Cu^IV?O oxo species as a catalytic intermediate is proposed for the catalytic process. Copyright © 2008 John Wiley & Sons, Ltd.     

Template Syntheses of Copper(II) Complexes from Arylhydrazones of Malononitrile and their Catalytic Activity towards Alcohol Oxidations and the Nitroaldol Reaction: Hydrogen Bond‐Assisted Ligand Liberation and E/Z Isomerisation

A one‐pot template condensation of 2‐(2‐(dicyanomethylene)hydrazinyl)benzenesulfonic acid (H₂L¹, 1 ) or 2‐(2‐(dicyanomethylene)hydrazinyl)benzoic acid (H₂L², 2 ) with methanol (a), ethylenediamine (b), ethanol (c) or water (d) on copper(II), led to a variety of metal complexes, that is, mononuclear [Cu(H₂O)₂(κO¹,κN² L^1a] ( 3 ) and [Cu(H₂O)(κO¹,κN³ L^1b)] ( 4 ), tetranuclear [Cu₄(1 κO¹,κN²:2 κO¹ L^2a)₃‐(1 κO¹, κN²:2 κO² L^2a)] ( 5 ), [Cu₂(H₂O)(1 κO¹, κN²:2 κO¹ L^2c)‐(1 κO¹,1 κN²:2 κO¹,2 κN¹‐ L^2c)]₂ ( 6 ) and [Cu₂(H₂O)₂(κO¹,κN²‐ L^1dd)‐(1 κO¹,κN²:2 κO¹ L^1dd)(μ‐H₂O)]₂ ? 2 H₂O ( 7? 2 H₂O), as well as polymer‐ ic [Cu(H₂O)(κO¹,1 κN²:2 κN¹ L^1c)]_n ( 8 ) and [Cu(NH₂C₂H₅)(κO¹,1 κN²:2 κN¹L^2a)]_n ( 9 ). The ligands 2‐SO₃H‐C₆H₄‐(NH)N?C{(CN)[C(NH₂)‐(?NCH₂CH₂NH₂)]} (H₂L^1b, 10 ), 2‐CO₂H‐C₆H₄‐(NH)N?{C(CN)[C(OCH₃)‐(?NH)]} (H₂L^2a, 11 ) and 2‐SO₃H‐C₆H₄‐(NH)N?C{C(?O)‐(NH₂)}₂ (H₂L^1dd, 12 ) were easily liberated upon respective treatment of 4 , 5 and 7 with HCl, whereas the formation of cyclic zwitterionic amidine 2‐(SO₃^?)? C₆H₄? N?NC(? C?(NH⁺)CH₂CH₂NH)(?CNHCH₂CH₂NH) ( 13 ) was observed when 1 was treated with ethylenediamine. The hydrogen bond‐induced E/Z isomerization of the (HL^1d)^? ligand occurs upon conversion of [{Na(H₂O)₂(μ‐H₂O)₂}(HL^1d)]_n ( 14 ) to [Cu(H₂O)₆][HL^1d]₂ ? 2 H₂O ( 15 ) and [{CuNa(H₂O)‐(κN¹,1 κO²:2 κO¹ L^1d)₂}K_0.5(μ‐O)₂]n ? H₂O ( 16 ). The synthesized complexes 3 – 9 are catalyst precursors for both the selective oxidation of primary and secondary alcohols (to the corresponding carbonyl compounds) and the following diastereoselective nitroaldol (Henry) reaction, with typical yields of 80–99 %.     

Coinage (Cu,Ag) metal derivatives of salicylaldehyde N-ethylthiosemicarbazone: synthesis,spectroscopy, and structures

Reactions of copper(I) halides with triphenyl phosphine in acetonitrile followed by the addition of salicylaldehyde N-ethylthiosemicarbazone {(2-OH–C₆H₄)(H)C²=N³–N²H–C¹(=S)N¹HEt, H₂stsc-NEt} in chloroform in 1?:?2?:?1 (Cl) or 1?:?1?:?1 (Br, I) molar ratios yield mononuclear, [CuCl(η ¹-S-H₂stsc-NHEt)(PPh₃)₂] (1) and sulfur-bridged dinuclear, [Cu₂X₂(μ-S-H₂stsc-NEt)₂(PPh₃)₂] (X?=?Br, 4; I, 5) complexes. Similarly, reaction of silver halides (Cl, Br) with H₂stsc-NEt in acetonitrile followed by the addition of PPh₃ to the solid that formed (1?:?1?:?2 molar ratio), yielding mononuclear complexes, [AgX(η ¹-S-H₂stsc-NHEt)(PPh₃)₂] (Cl, 2; Br, 3). All these complexes are characterized with analytical data, IR, and NMR spectroscopy and single-crystal X-ray crystallography. The ligand favored η ¹-S bonding in 1, 2, and 3, and μ-S bonding in 4 and 5. Cu?···?Cu contacts were 3.063?Å. The complexes form 1-D or 2-D H-bonded networks, entrapping solvent in some cases.     

An Adaptable N‐Heterocyclic Carbene Macrocycle Hosting Copper in Three Oxidation States

A neutral hybrid macrocycle with two trans‐positioned N‐heterocyclic carbenes (NHCs) and two pyridine donors hosts copper in three oxidation states (+I–+III) in a series of structurally characterized complexes ( 1 – 3 ). Redox interconversion of [LCu]^+/2+/3+ is electrochemically (quasi)reversible and occurs at moderate potentials (E_1/2=?0.45 V and +0.82 V (vs. Fc/Fc⁺)). A linear C^NHC‐Cu‐C^NHC arrangement and hemilability of the two pyridine donors allows the ligand to adapt to the different stereoelectronic and coordination requirements of Cu^I versus Cu^II/Cu^III. Analytical methods such as NMR, UV/Vis, IR, electron paramagnetic resonance, and Cu Kβ high‐energy‐resolution fluorescence detection X‐ray absorption spectroscopies, as well as DFT calculations, give insight into the geometric and electronic structures of the complexes. The XAS signatures of 1 – 3 are textbook examples for Cu^I, Cu^II, and Cu^III species. Facile 2‐electron interconversion combined with the exposure of two basic pyridine N sites in the reduced Cu^I form suggest that [LCu]^+/2+/3+ may operate in catalysis via coupled 2 e^?/2 H⁺ transfer.     

Reactions of Copper(II) Chloride in Solution: Facile Formation of Tetranuclear Copper Clusters and Other Complexes That Are Relevant in Catalytic Redox Processes

Mixing CuCl₂ ? 2 H₂O with benzylamine in alcoholic solutions led to an extremely colorful chemistry caused by the formation of a large number of different complexes. Many of these different species could be structurally characterized. These include relatively simple compounds such as [Cu(L¹)₄Cl₂] (L¹=benzylamine) and (HL¹)₂[CuCl₄]. Most interestingly is the easy formation of two cluster complexes, one based on two cluster units Cu₄OCl₆(L¹)₄ connected through one [Cu(L¹)₂Cl₂] complex and one based on a cubane‐type cluster ([Cu₄O₄](C₁₁H₁₄)₄Cl₄). Both clusters proved to be highly reactive in a series of oxidation reactions of organic substrates by using air or peroxides as oxidants. Furthermore, it was possible to isolate and structurally characterize ([Cu(L¹)Cl]₃ and [Cu(benz₂mpa)₂]CuCl₂ (benz₂mpa=benzyl‐(2‐benzylimino‐1‐methyl‐propylidene)‐amine), two copper(I) complexes that formed in solution, demonstrating the high redox activity of the cluster systems. In addition, it was possible to solve the molecular structures of the compounds Cu₄OCl₆(MeOH)₄, [Cu(MeOH)₂Cl₂], [Cu(aniline)₂Cl₂], and an organic side product (HC₁₃H₁₉NOCl). In fact all determined structures are of a known type but the chemical relation between these compounds could be explained for the first time. The paper describes these different compounds and their chemical equilibria. Some of these complexes seem to be relevant in catalytic oxidation reactions and their reactivity is discussed in more detail.     

Metal Derivatives of Thiosemicarbazones: Crystal and Mole­cular Structures of Mono‐ and Dinuclear Copper(II) Complexes with N1‐Subsitituted Salicylaldehyde Thiosemicarbazones

Reactions of copper(II) acetate with N¹‐subsitituted salicylaldehyde thiosemicarbazones [R¹R²C²=N³–N²H–C¹(=S)–N¹HR³;R¹ = 2‐HO–C₆H₄–, R² = H : R³ = Me (H₂L¹), Et (H₂L²)] are described. Copper(II) acetate was reacted with H₂L¹ and H₂L² ligands in the presence of polypyridyl co‐ligands, and this led to the formation ofmononuclear complexes, [Cu(κ³‐O, N, S‐L¹)(κ²‐N, N‐bipy)] ( 1 ),[Cu(κ³‐O, N, S‐L)(κ²‐N, N‐phen)] [L = L¹ ( 3 ), L² ( 4 )], [Cu(κ³‐O, N, S‐L)(κ²‐N, N‐tmphen)] [L =L¹ ( 5 ), L² ( 6 )] and a dinuclear complex, [Cu₂L²₂(bipy)] ( 2 ) (bipy = 2, 2′‐bipyridine, phen = 1, 10‐phenanthroline, tmphen = 3, 4, 7, 8‐tetramethyl‐1, 10‐phenanthroline). In dinuclear complex 2 , one ligand is O, N³,S‐chelating, while second is O, N³,S‐chelation‐cum‐N²‐bridging; and in all others thio‐ligands are O, N³,S‐chelating. The μ_eff values for the complexes lie in the range of 1.79–1.83 BM. Complexes 1 , 3 – 6 have square pyramidal arrangement, whereas complex 2 has two independent molecules in the crystal lattice, and each molecule has trigonal bipyramidal square planar (5:4) coordination pair. Complexes 2 , 4 , and 6 showed fluorescence properties.