Trans-1,2-bis(diphenylphosphino)ethene as bridging ligand in thione-S-ligated dimeric copper(I) chloride complexes

Several mixed-ligand complexes have been prepared by treatment of copper(I) chloride with equimolar amounts of trans-1,2-bis(diphenylphosphino)ethene (trans-dppen) in acetonitrile followed by the addition of a methanolic solution of one equivalent of a heterocyclic thione (L). The novel complex compounds have been characterized by single-crystal X-ray diffraction, ¹H NMR and IR spectroscopy as well as by elemental analyses and melting points. The X-ray structures of three examples confirm that the compounds are homobimetallic dimers of type [CuCl(μ₂-trans-dppen)(L)]₂ containing two tetrahedral coordination units joined by two trans-dppen bridges.     

Copper(I) bromide complexes from 1,2-bis(diphenylphosphano) benzene and some heterocyclic thiones

The synthesis, characterization and solid state emission properties of a series of mixed-ligand copper(I)bromide complexes containing 1,2-bis(diphenylphosphano)benzene (dppbz) and some heterocyclic thiones (L) are reported. The complexes are readily synthesized by the addition of the appropriate thione to a CuBr-diphosphane adduct in acetonitrile/methanol or acetone solution. The molecular structures of [CuBr(dppbz)(py2SH)], [CuBr(dppbz)(pymtH)] and [CuBr(dppbz)(imdtH₂)] were established by single-crystal X-ray diffraction. Each of these structures features a tetrahedral copper(I) centre with two phosphorus atoms from the chelating diphos ligand, one bromine and the exocyclic sulfur atom of the heterocyclic thioamide unit. Slow decomposition of the mixed-ligand complexes via ligand dissociation occurs when their chloroform solutions are left to stand at room temperature for several weeks. On the basis of elemental analysis, NMR and IR spectra, the resulting coloured crystals are found to contain phosphane-free coordination polymers of composition [CuBr(L)]. At room temperature, some of the molecular complexes in the solid state exhibit strong emission assigned to a metal-ligand charge transfer of type Cu(I) → π*(PPh₂).     

Silver(I) complexes with heterocyclic thiones and tertiary phosphines as ligands. Part 4. Dinuclear complexes of silver(I) bromide: the crystal structure of bis[bromo-(pyrimidine-2-thione)(triphenylphosphine)silver(I)]

Mixed-ligand complexes of the formula [Ag(PPh₃)(L)Br]₂ were obtained by treatment of various heterocyclic thiones L {L=pyridine-2-thione (py2SH), pyrimidine-2-thione (pymtH), benz-1,3-imidazoline-2-thione (bzimtH₂), benz-1,3-thiazoline-2-thione (bztztH), 1-methyl-1,3-imidazoline-2-thione (meimtH) and 5-methoxy-benz-1,3-imidazoline-2-thione (5MeObzimtH₂)} with equivalent quantities of silver(I) bromide and triphenylphosphine in dry acetone. The compounds were characterized by their IR, far-IR, UV–Vis and ¹H NMR spectroscopic data. The crystal structure of [Ag(PPh₃)(pymtH)Br]₂ was determined by single-crystal X-ray diffraction methods. The complex exhibits a planar Ag₂Br₂ moiety in which each of the doubly bromine-bridged Ag(I) centres is further bonded to one phosphine P and one thione S atom.     

Synthesis and crystal structure of one-dimensional zinc(II) polymer constructed by salicylate and trans-1,2-bis(4-pyridyl)ethylene

A new zinc(II) compound, [Zn₂(Hsal)₄(4,4′-bpe)₂] · [Zn(Hsal)₂(4,4′-bpe)(DMF)(H₂O)] · CH₃OH (1) (Hsal = salicylate and 4,4′-bpe = trans-1,2-bis(4-pyridyl)ethylene) has been synthesized and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, and single crystal X-ray diffraction. The crystal structure consists of three independent moieties: [Zn₂(Hsal)₄(4,4′-bpe)₂], [Zn(Hsal)₂(4,4′-bpe)(DMF)(H₂O)], and non-coordinated CH₃OH molecule. In the compound two independent moieties which are connected by 4,4′-bpe to form 1-D chains, respectively, are further expended to accomplish 2-D network through hydrogen-bonding interactions between non-coordinated methanol and coordinated water molecule or carboxylate oxygen atoms of Hsal ligands.     

Diphosphines as bridging ligands in polymeric and dimeric thione-S-ligated Ag(I) nitrate complexes

Reactions of silver(I) nitrate with equimolar amounts of the diphos ligands 1,4-bis(diphenylphosphino)butane (dppb) or 1,2-bis(diphenylphosphino)ethane (dppe) and some heterocyclic thiones (L) in acetonitrile/methanol solvent afforded mixed-ligand complexes, the nature of which was found to be strongly influenced by the backbone length of the diphosphine ligand. The longer chained diphos ligand formed a series of dinuclear complexes of the type [Ag(dppb)(L)]₂(NO₃)₂ with both the diphosphine and thione ligands acting as bridging ligands between the two four-coordinate pseudo-tetrahedrally coordinated metal centers. In the unique case of L=4-methyl-5-trifluoromethyl-4H-1,2,4-triazoline-3(2H)-thione (mftztH), the reaction proceeded under exclusion of the thione ligand from the coordination sphere and coordination of the nitrate anions instead, leading to the diphosphine-doubly bridged dimeric compound [Ag(dppb)(NO₃)]₂. On the other hand, the complexes produced when using the short bite 1,2-bis(diphenylphosphino)ethane (dppe) turned out to be diphosphine-bridged cationic polymers of the type [Ag(dppe)(L)₂]_n(NO₃)_n. The structures of one representative for each of the two aforementioned series of complex compounds, namely [Ag(dppb)(py2SH)]₂(NO₃)₂ · 2H₂O and [Ag(dppe)(pymtH)₂]_n(NO₃)_n, have been established by single-crystal X-ray diffraction.     

Synthesis, characterization, crystal structures and photophysical properties of copper(I) complexes containing 1,1′-bis(diphenylphosphino)ferrocene (B-dppf) in doubly-bridged mode

Five copper(I) complexes having general formula [Cu₂(μ-X)₂(κ²-P,P-B-dppf)₂] (X = Cl(1), Br(2), I(3), CN(4), and SCN(5)) were prepared starting with CuX and B-dppf in 1:1 molar ratio in DCM-MeOH (50:50 V/V) at room temperature. The complexes have been characterized by elemental analyses, IR, ¹H NMR, ³¹P NMR and electronic spectral studies. Molecular structures for 1, 2 and 4 were determined crystallographically. Complexes 1, 2 and 4 exist as centrosymmetric dimers in which the two copper atoms are bonded to two bridging B-dppf ligands and two bridging (pseudo-)halide groups in a μ-η¹ bonding mode to generate nearly planar Cu₂(μ-η¹-X)₂ framework. Both bridging B-dppf ligands are arranged in antiperiplanar staggered conformation in 1 and 2 (mean value 56.40-56.76°), and twisted from the eclipsed conformation (mean value 78.19°) in 4. The Φ angle value in 4 is relatively larger as compared to 1 and 2. This seems to indicate that the molecular core [Cu₂(μ-η¹-X)₂] in 4 is a sterically demanding system that forces the B-dppf ligand to adopt a relatively strained conformation in comparison to less strained system in 1 and 2. All the complexes exhibit moderately strong luminescence properties in the solution state at ambient temperature.     

Syntheses and structural characterization of dicopper(I) bis(diphenylphosphino)acetylene complexes containing tricyclic, cyclic and linear frameworks

The complexes [Cu₂(dppa)₃(CH₃CN)₂][BF₄]₂ (1) and Cu₂(dppa)₃(O₃SCF₃)₂ (2) have been prepared in good yields by treating [Cu(MeCN)₄][BF₄] and [Cu(MeCN)₄][O₃SCF₃], respectively, with Ph₂PCCPPh₂ (abbreviated as dppa) at room temperature. The reaction of 1 with di-2-pyridyl ketone (abbreviated as dpyk) produces [Cu₂(dppa)₂(dpyk)₂][BF₄]₂ (3), and with 1,1′-bis(diphenylphosphino)ferrocene (abbreviated as dppf) produces [Cu₂(dppa)(dppf)₂][BF₄]₂ (4). The molecular structures of 1-4 have been determined by an X-ray diffraction study. Compounds 1 and 2 form a helical Cu₂(dppa)₃ metallatricycle, compounds 3 forms a Cu₂(dppa)₂ metallacycle, and compound 4 contains a linear Cu₂(dppa) skeleton.     

Copper(I) halide chelates of the wide bite angle diphosphane xantphos: Crystal structures of [CuBr(xantphos)(dmpymtH)] and [CuI(xantphos)(imdtH2)] · CH3CN

Copper(I) halide complexes containing the diphosphane xantphos (4,5-bis(diphenylphosphano)-9,9-dimethyl-xanthene) and some heterocyclic thione ligands have been synthesized and characterized by ¹H NMR, IR spectroscopy, elemental analyses and melting point determinations. The complexes can be readily obtained by the addition of the thione ligand to a CuX-diphosphane adduct in acetonitrile/methanol solution. The molecular structures of [CuBr(xantphos)(dmpymtH)] and [CuI(xantphos)(imdtH₂)] · CH₃CN have been established by single-crystal X-ray diffraction. Each of these structures features a tetrahedral copper(I) center with two phosphorus atoms from the chelating diphos ligand, one halogen atom and the exocyclic sulfur atom of the heterocyclic thioamide unit. Rapid decomposition of the mixed-ligand complexes via ligand dissociation occurs upon standing of their acetonitrile solutions at room temperature for several days. The resulting colored crystals, which not only on elemental analysis but also on the basis of their NMR and IR spectra, are found to be phosphane-free coordination polymers of composition [CuX(thione)].     

Copper(I) complexes with Schiff base and 1,2-bis(diphenylphosphino)ethane as ligands: Synthesis, structure and catalytic properties for the amination of aryl halide

Some copper(I) complexes of the type [Cu(L)(dppe)]X (1-4) [where L = (3-trifluoromethylphenyl)pyridine-2-ylmethylene-amine; dppe = 1,2-bis(diphenylphosphino)ethane; X = Cl⁻, CN⁻, ClO₄⁻ and BF₄⁻] have been synthesized by the condensation of 3-aminobenzotrifluoride with 2-pyridinecarboxaldehyde followed by the reaction with CuCl, CuCN, [Cu(MeCN)₄]ClO₄ and [Cu(MeCN)₄]BF₄ in presence of dppe. The complexes 1-4 were then characterized on the basis of elemental analysis, IR, UV-Vis and ¹H NMR spectral studies. The representative complex of the series 4 has been characterized by single crystal X-ray diffraction which reveal that in complex the central copper(I) ion assumes the irregular pseudo-tetrahedral geometry. The catalytic activity of the complexes was tested and it was found that all the complexes worked as effective catalyst in the amination of aryl halide.     

Copper(I) complexes of N-thioacylamido(thio)phosphates and triphenylphosphine

Heteroligand copper(I) complexes of bi- or bis-bidentate acylamidophosphates PhC(S)NHP(S)(OPr-i)₂, PhC(S)NHP(O)(OPr-i)₂, Et₂NC(S)NHP(S)(OPr-i)₂, PhNHC(S)NHP(S)(OPr-i)₂, N-(4-aminobenzo-15-crown-5)-C(S)NHP(S)(OPr-i)₂, N,N-(1,10-diaza-18-crown-6)-[C(S)NHP(S)(OPr-i)₂]₂, and triphenylphosphine were prepared and characterised. Copper is bound by two PPh₃ and one SCNPX (X = O, S) fragment of chelating ligand in all cases. Triphenylphosphine molecules reversibly dissociate in solution. Details of the X-ray structures of (Ph₃P)₂Cu[PhC(S)NP(S)(OPr-i)₂] and (Ph₃P)₂Cu[Et₂NC(S)NP(S)(OPr-i)₂] are reported.     

Chair-form [Ag2(1,2-bimb)2] in silver(I) complexes containing the ditopic ligand 1,2-bis(1-imidazolylmethyl)benzene (1,2-bimb)

The ditopic ligand 1,2-bis(1-imidazolylmethyl)benzene (1,2-bimb) and its silver(I) complexes [Ag₂(1,2-bimb)₂](PF₆)₂ (1) and {[Ag₂(1,2-bimb)₂]₂(SbF₆)₄}_n (2) were prepared and their structures characterized by X-ray crystallography. Both complexes contain the chair-form unit [Ag₂(1,2-bimb)₂]²⁺ with Ag(I) linearly coordinated by N_Im (Im=1-imidazolyl) from the Im groups of two 1,2-bimb. However, the [Ag₂(1,2-bimb)₂]²⁺ units are positioned differently in forming 1D infinite chains through weak argentophilic interactions: linear chains in 1 with the units oriented in same direction are formed via Ag?π interactions, while polymeric chains constructed via Ag?Ag interactions in 2 are observed with the units arranged in alternate directions. Differences in supramolecular structures may be a result of different size of the anions.     

Copper(II) complexes with 2-N-(picolinylidene)-n-R-phenols: Solvatochromism, self-assembly and supramolecular structures

A series of copper(II) complexes having the formula [Cu(n-R-pyp)X] with the N,N,O-donor Schiff base system 2-N-(picolinylidene)-n-R-phenol (n-R-Hpyp) (where n = 3, 4, 5 and 6, when R = Me and n = 4 when R = Cl) and halide (X⁻ = Cl⁻ or Br⁻) as an ancillary ligand have been synthesized. The complexes are characterized by microanalytical, magnetic and various spectroscopic measurements. They display solvatochromic behavior. Single crystal X-ray structures of all the complexes are determined. In coordinatively unsaturated species such as a square-planar complex, the metal ion can interact with a fifth atom and if this atom is metal bound, dimeric or polymeric aggregate is formed. In the present series of complexes, the metal ions are square-planar and distorted square-pyramidal when there is an intermolecular Cu···X interaction. In addition to this Cu···X interaction, presence of intermolecular weak non-covalent interactions namely O-H···O, C-H···O, C-H···X and π···π are perceived. The supramolecular architectures formed by the molecules of these complexes via these interactions are scrutinized. The observed supramolecular structural motifs can be classified as staircase, ladder, brick-wall and square-grid. Except for R = Cl the analogous chloride and bromide coordinated complexes show similar structural features.     

Dinuclear and mononuclear copper(II) carboxylate complexes with cis-chelating diacids

The synthesis and crystal structures of two new copper complexes with chelating dicarboxylic acids are described. Reaction of copper(II) acetate with diacid H₂L2 (HO₂CC(Me)₂OArOC(Me)₂CO₂H, Ar=1,3-substituted phenyl) gave a bischelate complex (L2)₂Cu₂ · 2MeOH with the normal paddlewheel structure and tilted, trans-oriented chelate rings with skewed conformations. The overall structure was reasonably well reproduced by density functional calculations on (L2)₂Cu₂. Treatment of the product from reaction of Cu₂(OAc)₄ and diacid H₂L3 (Ar=1,3-substituted 2,4-dibromophenyl) with pyridine gave a six-coordinate mononuclear chelate (L3)Py₂Cu · H₂O in which one chelate carboxylate is monodentate, the other is unsymmetrically bidentate, and the pyridines are cis-coordinated.     

Syntheses and characterization of luminescent dinuclear and polynuclear Cu(I) complexes containing 4,4′-bis(diphenylphosphino)biphenylene bridge

The dinuclear complex [Cu₂(dpbp)₂(NCMe)₄][BF₄]₂ (1) has been prepared by treating [Cu(NCMe)₄][BF₄] with 4,4′-bis(diphenylphosphino)biphenylene (abbreviated as dpbp). Reactions of 1 with 2,2′-bipyridine and 1,1′-bis(diphenylphosphino)ferrocene (abbreviated as dppf) afford [Cu₂(dpbp)₂(2,2′-bipy)₂][BF₄]₂ (2) and [Cu₂(dpbp)(dppf)₂][BF₄]₂ (3), respectively. In contrast, compound 1 reacts with tetra(2-pyridyl)ethyl-1,4-diaminobutane (abbreviated as tpyda) to produce the polymeric complex {[Cu₂(dpbp)(tpyda)][BF₄]₂}_n (4). Compounds 1-4 are photoluminescent with the emission band (λ_max) in the range 510-554 nm. The crystal structures of 1 and 4 have been determined by an X-ray diffraction study.     

Synthesis, structure and spectroscopic properties of 2,3-bis(diphenylphosphino)quinoxaline (dppQx) and its copper(I) complexes

Phosphinoquinoxalines were prepared by treatment of 2,3-dichloroquinoxaline (3) with phosphorus nucleophiles. The Arbuzov reaction of 3 with PPh(O-i-Pr)₂ gave a mixture of diastereomers of 2,3-(PPh(O)(O-i-Pr))₂quinoxaline (6); the crystal structure of rac-6 was determined, but attempts at reduction to yield bis(phenylphosphino)quinoxaline 7 resulted in P-C cleavage and formation of phenylphosphine. The bis(secondary phosphine) 7 could be generated from 3 and LiPHPh(BH₃), but was not isolated in pure form. Copper-catalyzed coupling of PHPh₂ with 3 gave 2,3-bis(diphenylphosphino)quinoxaline (4, dppQx), whose coordination chemistry was investigated, with comparison to data for the analogous 1,2-bis(diphenylphosphino)benzene (dppBz) complexes. Reaction of dppQx with [Cu(NCMe)₄][PF₆] gave [Cu(dppQx)₂][PF₆] (8); CuCl yielded [Cu(dppQx)Cl]₂ (9). Reaction of [Cu(NCMe)₄][PF₆] with one equiv of DPEphos, followed by one equiv of dppQx, gave [Cu(dppQx)(DPEphos)][PF₆] (10). Ligand 4 and copper complexes 8 and 9 were crystallographically characterized. The UV-Vis spectra of dppQx and its copper complexes were red-shifted from those of the dppBz analogs; in contrast to results for the dppBz complexes, those of dppQx were not luminescent in solution.     

Synthesis, characterization, and crystal structures of hydrotris(2-mercapto-1-imidazolyl)borate-based zinc(II) and copper(I) complexes

The reaction of the tripod ligand hydrotris(2-mercapto-1-imidazolyl)borate Tm^xylyl with zinc(II) perchlorate in methanol afforded the mononuclear complex of the type [Tm^xylyl-Zn(mim^xylyl)]ClO₄ (1). Whereas under the same conditions, the reaction with copper(II) perchlorate gives rise to the simultaneous formation of the dinuclear copper(I) complex [Tm^xylylCu]₂ (2). The chemical formulae of the complexes have been characterized by elemental chemical analysis, IR-NMR spectroscopies, and single crystal X-ray methods. In complex 1, the zinc(II) atom displays a distorted tetrahedral environment. While in complex 2, the Tm^xylyl ligand bridges the two copper(I) atoms in an asymmetric manner with trigonal geometry. The inverted conformation of the ligand Tm^xylyl at the boron center, allows the B-H units to be directed towards the copper centers. The greater reactivity of the borohydride groups towards metal centers enhances the reduction of Cu(II) to Cu(I). The obtained kinetic results for the methylation reactions of 1 and 2 indicate that these bound thione complexes are less suitable to electrophilic attack than the thiolate ligand.     

Equilibrium and structural studies on Co(II), Ni(II), Cu(II) and Zn(II) complexes with N-(2-benzimidazolyl)methyliminodiacetic acid: crystal structures of Ni(II) and Cu(II) complexes

Combined pH-metric, UV-Vis, ¹H NMR and EPR spectral investigations on the complex formation of M(II) ions (M=Co, Ni, Cu and Zn) with N-(2-benzimidazolyl)methyliminodiacetic acid (H₂bzimida, hereafter H₂L) in aqueous solution at a fixed ionic strength, I=10⁻¹ mol dm⁻³, at 25 ± 1 °C indicate the formation of M(L), M(H₋₁L)⁻ and M₂(H₋₁L)⁺ complexes. Proton-ligand and metal-ligand constants and the complex formation equilibria have been elucidated. Solid complexes, [M(L)(H₂O)₂] · nH₂O (n=1 for M = Co and Zn, n=2 for M = Ni) and {Cu (μ-L) · 4H₂O}_n, have been isolated and characterized by elemental analysis, spectral, conductance and magnetic measurements and thermal studies. Structures of [Ni(L)(H₂O)₂] · 2H₂O and {Cu(μ-L) · 4H₂O}_n have been determined by single crystal X-ray diffraction. The nickel(II) complex exists in a distorted octahedral environment in which the metal ion is coordinated by the two carboxylate O atoms, the amino-N atom of the iminodiacetate moiety and the pyridine type N-atom of the benzimidazole moiety. Two aqua O atoms function as fifth and sixth donor atoms. The copper(II) complex is made up of interpenetrating polymeric chains of antiferromagnetically coupled Cu(II) ions linked by carboxylato bridges in syn-anti (apical-equatorial) bonding mode and stabilized via interchain hydrogen bonds and π-π stacking interactions.     

Synthesis and characterization of the 1:1 adducts of copper(I) halides with bidentate N,N′-bis(benzophenone)-1,2-diiminoethane Schiff base: Crystal structures of [Cu(bz2en)2][CuX2] (X = Br, I) complexes

1:1 adducts of N,N′-bis(benzophenone)-1,2-diiminoethane (bz₂en) with copper(I) chloride, bromide and iodide, [Cu(bz₂en)₂][CuX₂] (X = Cl, Br, and I), have been synthesized and the structures of the solid bromide and iodide adducts were determined by X-ray crystallography from single-crystal data. The solid-state structure reveals ionic complexes containing a cation of copper(I) ion coordinated to four nitrogen atoms of two bz₂en molecules (distorted tetrahedron) and a linear dibromocuprate(I) and a di-μ-iodo-diiododicuprate(I) anion for the bromo and iodo adducts, respectively. The bromo adduct structure contains CH?Br intermolecular hydrogen bonds. The complexes are very stable towards atmospheric oxygen in the solid state. The spectral properties of the above complexes are also discussed.     

Syntheses and characterization of copper complexes with the ligand 2-aminoethyl(2-pyridylmethyl)-1,2-ethanediamine (apme)

Copper(I)/(II) complexes with the ligand 2-aminoethyl(2-pyridylmethyl)1,2-ethanediamine (apme, abbreviated as PDT in the literature as well) were prepared and characterized. Crystal structures of the copper(I) complexes, [Cu₂(apme)₂]X₂ (1, 2; X = ClO₄, CF₃SO₃), showed that they are dinuclear, in contrast to the trigonal bipyramidal copper(II) complexes [Cu(apme)Cl]BPh₄ (3) and [Cu(apme)(DMF)](BPh₄)₂ (4). 1 and 2 could be investigated in solution by NMR spectroscopy and 3 and 4 by cyclovoltammetry. From the results of these studies it is clear that in solution equilibria between the dinuclear complexes 1/2 and another species exist, most likely the monomeric [Cu(apme)CH₃CN]⁺. Time-resolved UV/vis spectra at low temperatures allowed the spectroscopic detection of dioxygen adduct complexes as reactive intermediates during the oxidation of 1/2 with dioxygen that seem to play an important role in copper enzymes such as peptidylglycine--hydroxylating monooxygenase (PHM).     

A new tyrosinase model with 1,3-bis[(2-dimethylaminoethyl)iminomethyl]benzene: Binuclear copper(I) and phenoxo/hydroxo-bridged dicopper(II) complexes

The ligand 1,3-bis[(2-dimethylaminoethyl)iminomethyl]benzene (baib) reacts with [Cu(MeCN)₄][ClO₄] to form a binuclear copper(I) complex . Crystal structure analysis reveals that the distorted tetrahedral coordination of each copper(I) center is satisfied by one bidentate arm of each ligand. The complex undergoes ready aromatic ring hydroxylation at position 2 of the phenyl ring when reacted with molecular oxygen in MeCN/MeOH/CH₂Cl₂, producing a four-coordinate μ-phenoxo- and μ-hydroxo-bridged dicopper(II) complex, [Cu₂(baib-O)(OH)(OClO₃)₂] · 1.5H₂O (2) (baib-OH: 1,3-bis[(2-dimethylaminoethyl)iminomethyl]phenol). This reaction mimics the reactivity of the copper monooxygenase tyrosinase. A trend is observed for the extent of aromatic ring hydroxylation (25 °C): MeCN > MeOH > CH₂Cl₂. Cyclic voltammetric experiment of 1 in MeCN reveals an appreciably high redox potential (anodic peak potential, E_pa = 0.69 V versus SCE) for the redox process. Complex 2 has been characterized by single-crystal X-ray crystallography. Variable temperature (60-300 K) magnetic susceptibility measurements on 2 establish that the copper(II) centers in 2 are antiferromagnetically coupled (2J = −280 cm⁻¹).