Synthesis,crystal structure,magnetic and spectroscopic properties of {[Cu(oxbe)(py)]2Ni(py)2}·2Dmf complex of dissymmetrical oxamidate

The trinuclear complex {[Cu(oxbe)(py)]₂Ni(py)₂}·2DMF has been prepared and characterized by elemental analysis, IR and electronic spectra and magnetic susceptibility, where H₃oxbe is the dissymmetrical ligand N-benzoato-N′-(2-aminoethyl) oxamido, py?=?pyridine, DMF?=?dimethylformamide. The molecular structure of this complex is centrosymmetrical and has an extended oxamido-bridged structure consisting of two pyramidal copper(II) and one octahedral nickel(II) ions. The central Ni(II) and two terminal Cu(II) ions are antiferromagnetically coupled, J?=???60.2?cm^?1.     

The effect of ligand basicity on the thermal stability of heterodinuclear NiII–ZnII complexes

Four complexes of the nuclear structure Ni^II–Zn^II were prepared with bis-N,N′-(salicylidene)-1,3-propanediamine (LH₂), bis-N,N′-(salicylidene)-2,2′-dimethyl-1,3-propanediamine (LDMH₂) and the reduced derivatives of these Schiff bases, bis-N,N′-(2-hydroxybenzyl)-1,3-propanediamine (L^HH₂), bis-N,N′-(2-hydroxybenzyl)-2,2′-dimethyl-1,3-propanediamine (LDM^HH₂). The complexes were characterized using IR spectroscopy, elemental analysis and thermogravimetric methods. The stoichiometry of the complex molecules were found to be NiL·ZnCl₂·(DMF)₂, NiLDM·ZnCl₂·(DMF)₂, NiL^H·ZnCl₂·(DMF)₂ and NiLDM^H·ZnCl₂·(DMF)₂. The molecular models of the complexes prepared with the reduced Schiff bases were determined according to the X-ray diffraction method. It is seen that in these complexes Ni(II) is in octahedral and Zn(II) is in tetrahedral coordination sphere. Ni(II) ion is coordinated between two nitrogen and two oxygen donors of the ligand and oxygen donors of the two DMF molecules. Zn(II) ion on the other hand is coordinated between two oxygen of the organic ligand forming two μ bonds. It also coordinates two Cl ions. The thermogravimetric analysis showed that the complex NiLDM^H·ZnCl₂·(DMF)₂ containing methyl groups is more stable than the other complex NiL^H·ZnCl₂·(DMF)₂ containing reduced Schiff base. The coordinative DMF molecules in NiLDM^H·ZnCl₂·(DMF)₂ were thermally cleaved. However, the cleavage of DMF molecules NiL^H·ZnCl₂·(DMF)₂ resulted in the thermal degradation of the complex. In order to explain the TG data of the ligands were titrated in non-aqueous medium and their basicity strengths were determined. It was found that the basicity of the ligands containing two methyl groups were stronger. It is understood that the two methyl groups increase the negative charge density on nitrogen causing an increase in complex stability.     

Nickel(II) complexes with Schiff bases derived from salicylaldehyde or pentanedione and 3-aminopropanethiol

Template reactions of salicylaldehyde or pentanedione with 3-aminopropanethiol (Hapt) in the presence of Ni(II) ions are described. When salicylaldehyde was used, a dinuclear Ni(II) complex [Ni(bit′)]₂ (2) (H₂bit′?=?2-(3′-mercaptopropyliminomethyl)phenol) was obtained instead of the reported trinuclear one [Ni(bit)]₃ (1) (H₂bit?=?2-(2′-mercaptoethyliminomethyl)phenol) containing 2-aminoethanethiol (Haet). Starting from pentanedione, the expected dinuclear complex [Ni(pit′)]₂ (H₂pit′?=?2-(3′-mercaptopropylimino)pentanol) was not obtained, nor was [Ni(pit)]₂ (3) (H₂pit?=?2-(2′-mercaptoethylimino)pentanol). The complex was found to be a trinuclear Ni(II) complex [Ni{Ni(apt)₂}₂]²⁺ (4), as confirmed by elemental analysis, electronic and NMR spectra. Complexes 1 and 3 were also synthesized and their ¹³C, ¹H–¹H and ¹³C–¹H?NMR spectra are discussed in detail. The X-ray crystal structure of 2 shows that two Ni(II) ions are connected by the thiolate donor atom from each ligand, resulting in a four-membered ring. Differences in reactivity and properties is due to the presence of an additional methylene group in the aminoalkane arm of the ligand.     

Structurally characterized homotrinuclear Salamo‐type nickel(II) complexes: Synthesis,solvent effect and fluorescence properties

Four new solvent‐induced Ni(II) complexes with chemical formulae [{NiL(μ₂‐OAc)(MeOH)}₂Ni]·2MeOH ( 1 ), [{NiL(μ₂‐OAc)}₂(n‐PrOH)(H₂O)Ni]·n‐PrOH ( 2 ), [{NiL(μ₂‐OAc)(DMF)}₂Ni] ( 3 ) and [{NiL(μ₂‐OAc)(DMSO)}₂Ni]·2DMSO ( 4 ), (H₂L = 4‐Nitro‐4′‐chloro‐2,2′‐[(1,3‐propylene)dioxybis(nitrilomethylidyne)]diphenol) have been synthesized and characterized by elemental analyses, FT‐IR, UV–Vis spectra and X‐ray crystallography. X‐ray crystal structure determinations revealed that each of the Ni(II) complexes 1–4 consists of three Ni(II) atoms, two completely deprotonated (L)^2? units, two μ₂‐acetate ions and two coordinated solvent molecules (solvents are methanol, n‐propanol, water, N,N‐dimethylformamide and dimethyl sulphoxide, respectively). Although the four complexes 1–4 were synthesized in different solvents, it is worthwhile that the Ni(II) atoms in the four complexes 1–4 adopt hexa–coordinated with slightly distorted octahedral coordination geometries, and the ratios of the ligand H₂L to Ni(II) atoms are all 2: 3. The complexes 1–4 possess self‐assembled infinite 1D, 3D, 1D and 2D supramolecular structures via the intermolecular hydrogen bonds, respectively. In addition, fluorescence behaviors were investigated in the complexes 1–4 .     

An Unprecedented Trinuclear Nickel(II) Complex Assembled from an Asymmetric Salamo-Type Ligand

An unprecedented trinuclear Ni(II) complex assembled from an asymmetric Salamo-type ligand 6-ethoxy- 4′,6′-dichloro-2,2′-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol (H₂L) is synthesized. The Ni(II) complex with the general formula [Ni₃(L)₂(μ₃-OAc)₂]·3CH₃CN is characterized by IR, UV-vis, and fluorescence spectra and the single crystal X-ray analysis. All the Ni(II) atoms are hexacoordinated with slightly distorted octahedral symmetries. Interestingly, each Ni(II) atom is not located on the N₂O₂ cavity of the asymmetric Salamo-type (L)^2– unit, and two μ₃-OAc ions adopt an uncommon μ₃-η²:η¹ binding mode connecting the Ni1, Ni2, and Ni3 atoms. Furthermore, the crystallizing acetonitrile molecules successfully assemble into an infinite 2D network by hydrogen bonding and C–H···π interactions.     

Complex formation of Cu(II), Ni(II), Zn(II), Co(II), and Cd(II) acetates with 3,3′,4,4′,5,5′-hexamethyldipyrrolylmethene

The reactions of complex formation of Cu(II), Co(II), Zn(II), Ni(II), and Cd(II) acetates with 3,3′,4,4′5,5′-hexamethyl-2,2′-dipyrrolylmethene (HL) in DMF were studied by the electronic spectroscopy and calorimetric titration methods at 298.15 K. The main products of the above reactions are [ML₂] chelates. In the case of Cu and Ni salts, the process occurs through the spectrally recorded stage of formation of the heteroligand [ML(AcO)] complexes. The reaction with Cd acetate terminates at the stage of the heteroligand complex formation due to the large radius and decreasing electron affinity of the Cd²⁺ ion. The effect of the metal nature appears in the increasing thermodynamic stability of single-type complexes in the series [ML₂]: Ni(II) < Zn(II) < Co(II) < Cu(II) and [ML(AcO)]: Cd(II) < Ni(II) < Cu(II).     

Synthesis,crystal structure and magnetic properties of a nickel(II) complex containing a 2-pyridyl-substituted nitronyl nitroxide

A new complex of formula [Ni(NIT2Py)₂Cl(H₂O)]Cl·2CH₃OH, where NIT2Py is 2-(2′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, was synthesized and characterized structurally and magnetically. The structure consists of a [Ni(NIT2Py)₂Cl(H₂O)]⁺ ion, a chloride anion and two methanol molecules. The nickel(II) ion lies in a distorted octahedral environment; two nitrogen atoms and two oxygen atoms from NIT2Py ligands from the basal plane; one oxygen atom from a water molecule and one chloride anion occupy axial positions. Variable temperature magnetic susceptibility data show that there is strong antiferromagnetic coupling between the nickel(II) ion and nitronyl nitroxide radicals. The results suggest that the sign of the magnetic interaction depends on structural and ligand effects.     

Synthesis,crystal structure and magnetism of a two-dimensional Ni(II) coordination polymer with thiocyanate anion and dehydrogen-1,10-phenanthrolin-2-ol as bridging ligands

A two-dimensional coordination polymer [Ni(μ_1,3-SCN)(μ-Pheno)(CH₃OH)] _n (where Pheno = dehydrogen-1,10-phenanthrolin-2-ol) has been synthesized and its crystal structure determined by X-ray crystallography. Adjacent Ni(II) ions are coordinated by μ_1,3-SCN^? and μ-Pheno alternately forming a two-dimensional sheet structure. The fitting of the variable-temperature magnetic susceptibilities with a binuclear nickel(II) formula reveals that there is an anti-ferromagnetic interaction between the bridging Ni(II) ions with the magnetic coupling constant 2J = ?0.67 cm^?1.     

Two Supramolecular Nickel(II) Complexes: Syntheses,Crystal Structures and Solvent Effects

Two nickel(II) complexes, namely {[NiL(MeOH)(μ‐OAc)]₂Ni} · 2CH₂Cl₂ · 2MeOH ( 1 ) and {[NiL(EtOH)(μ‐OAc)]₂Ni} · 2EtOH ( 2 ) {H₂L = 5, 5′‐dimethoxy‐2, 2′‐[(ethylene)dioxybis(nitrilomethylidyne)]diphenol}, were synthesized and structurally characterized. Two trinuclear Ni^II complexes are both hexacoordinate around the central Ni^II atoms, showing octahedral coordination arrangements, and each complex comprises three divalent Ni^II atoms, two deprotonated L^2– ligands, in which four μ‐phenoxo oxygen atoms forming two [NiL(X)] (X = MeOH or EtOH) units, and coordinated and non‐coordinated solvent molecules. Complex 1 exhibits a 2D supramolecular network through intermolecular O–H ··· O, C–H ··· O and C–H ··· π interactions, whereas complex 2 forms an infinite 1D chain by intermolecular C–H ··· O hydrogen bonding interactions.     

Synthesis,structure and properties of a binuclear complex {[Mn(bpy)2(CuL)(H2O)2](ClO4)2} and its CuL precursor (H2L = 2,3-dioxo-5,6 : 14,15-dichlorobenzo-7,13-diphenyl-1,4,8,12-tetraazacyclo-pentadeca-7,12-diene)

A binuclear complex {[Mn(bpy)₂(CuL)(H₂O)₂](ClO₄)₂} (2) and its CuL (1) precursor (H₂L?=?2,3-dioxo-5,6?:?14,15-dichlorobenzo-7,13-diphenyl-1,4,8,12-tetraazacyclo-pentadeca-7,12-diene; bpy?=?2,2′-dipyridyl) have been synthesized and characterized structurally. Complex 1 consists of the neutral [CuL] fragments and methanol molecules. In complex 2, [Mn(bpy)₂(CuL)]²⁺ cation, two water molecules and two perchloric anions make up of the crystal. Mn(II) is coordinated by four nitrogen atoms from two 2,2′-dipyridyl and two oxygen atoms from the Cu(II) precursor. Magnetic characterization of 2 exhibits an antiferromagnetic interaction between Cu(II) and Mn(II) ions, with J?=??74.1?cm^?1.     

SYNTHESIS AND CRYSTAL STRUCTURE OF OXAMIDATO-BRIDGED BINUCLEAR COPPER(II) COMPLEXES

Abstract

The compounds [Cu(oxpn)] (1), [(bpy)(H₂O)Cu(μ-cis-oxpn)Cu(H₂O)] · 2NO₃ · 2H₂O (2) and [(Him)(NO₃)Cu(μ-trans-oxpn)Cu(Him)(NO₃)] (3), where oxpn is the dianion of N,N′-bis(3-aminopropyl)oxamide, bpy is bipyridine and Him is imidazole, were prepared and characterized by elemental analysis and IR spectra. Complex (2) was also studied by thermochemical analysis and its structure determined by X-ray crystallography. The structure of complex (2) consists of binuclear copper(II) molecules in which the copper(II) atoms are bridged by an oxamidato group in the cis conformation resulting a copper-copper distance of 5.21 Å. Both copper(II) ions are in square-pyramidal surroundings with almost coplanar basal planes and a water molecule occupying the apical positions. The N atoms of the oxamidato moiety are trigonal. Two lattice water molecules together with the two coordinated ones hydrogen bond with nitrate ions.     

The Structure of Nickel(Ii) and Copper(Ii) Complexes with 1,4,8,11-Tetraazacyclotetradecanein Aqueous Solution as Studied by the X-Ray Diffraction Method

The structure of 1,4,8,11-tetraazacyclotetradecane (cyclam) complexes with nickel(II) and copper(II) ions in aqueous solution has been determined by the x-ray diffraction method at 25°C. The [Ni-(cyclam)]²⁺ complex has a square-planar structure with four nitrogen atoms of the cyclam, and the Ni-N bond length has been determined to be 198 pm. Upon the addition of ammonia, the color of the nickel(II)-cyclam solution turns to deep purple and the [Ni(NH₃)₂(cyclam)]²⁺ complex is formed. The complex has a regular octahedral structure with an additional two NH₃ molecules along the axis vertical of the cyclam plane, and the Ni-N (NH₃ and cyclam) bond lengths are 209 pm. The copper(II)-cyclam complex in the aqueous solution is a distorted octahedron with two water molecules along the elongated axis. The axial Cu—O and equatorial Cu—N bond lengths are 277 and 210 pm, respectively.     

Steric interaction of solvation and sterically enhanced halogeno complexation of manganese(II), cobalt(II) and nickel(II) ions inN,N-dimethylacetamide

The complexation of manganese(II), cobalt(II) and nikel(II) with bromide ions has been studied in N,N-dimethylacetamide(DMA) by calorimetry and spectrophotometry. The formation of [MBr]⁺, [MBr₂] and [MBr₃]^– (M=Mn, Co, Ni) was revealed in all the metal systems. Interestingly, the complexation is significantly enhanced in DMA over N,N-dimethylformamide (DMF). This is unusual because physicochemical properties of DMA and DMF as solvent are similar. Furthermore, extracted electronic spectra of individual complexes of Ni^II suggested the presence of a geometry equilibrium, [NiBr(DMA)₅]⁺=[NiBr(DMA)₄]⁺+ DMA, in DMA. A similar geometry equilibrium is also suggested, [NiBr₂(DMA)₃]=[NiBr₂(DMA)₂]+DMA. Such geometry equilibria were not observed in DMF. With regard to cobalt(II), electronic spectra show the presence of the four-coordinated [CoBr(DMA)₃]⁺ complex in DMA, unlike the six-coordinated [CoBr(DMF)₅]⁺ one in DMF. These facts suggest that a specific strong steric interaction operates between coordinating solvent molecules, which plays a key role in the complexation behavior of the divalent transition metal ions in DMA.     

Synthesis,Structure, and Magnetic Behavior of a 1‐D Coordination Polymer [Ni(NIT4py)2(ip)(H2O)]n

A new coordination polymer of the formula [Ni(NIT4py)₂(ip)(H₂O)]_n(NIT4py = 2‐(4′‐pyridinyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide and ip = isophthalate dianion) has been synthesized and characterized by elemental analyses, IR spectrum, and single‐crystal X‐ray diffraction. The coordination about each Ni²⁺ ion is a distorted octahedra. Each isophthalate dianion binds two Ni²⁺ ions in monodentate‐bidentate mode, leading to a 1‐D chain. Among the chains, the coordinated water molecules and carboxylato oxygen atoms form hydrogen bonds, generating an infinite 1‐D ladder structure of a double‐chain. The magnetic study shows that the decrease of χ_MT value in the low temperature for the complex is mainly ascribed to the zero‐field splitting of the distorted octahedral Ni²⁺ ions.     

A trinuclear Ni(II) cluster with two significantly different configurations in the solid state

A chelating bisoxime ligand, 2,2′-[(1,3-propylene)dioxybis(nitrilomethylidyne)]dinaphthol (H₂L), and its corresponding Ni(II) cluster {[NiL(H₂O)]₂(OAc)₂Ni} · 0.5MeOH · 0.5CH₃CN · H₂O (1) have been synthesized and characterized by elemental analyses, TG-DTA, IR, ¹H NMR and X-ray diffraction methods. The Ni(II) cluster is monoclinic, space group P2(1)/c with cell dimensions a = 9.400(2), b = 24.530(4), c = 25.350(3) Å and β = 92.823(3)°. In the Ni(II) cluster, there are two ligand moieties (which provide N₂O₂ donors), two acetate ions and two water molecules, which result in three slightly distorted octahedral geometries around the Ni(II) ions.     

Square-planar nickel(II) complexes with a tridentate Schiff base and monodentate heterocycles: self-assembly to dimeric and one-dimensional array via hydrogen bonding

Square-planar nickel(II) complex with tridentate ONO-donor 4-[(2-hydroxyphenyl)imino]-2-pentanone (H₂hpac) and imidazole (Himdz) are reported. The complex was synthesized in moderate yield by reacting Ni(O₂CCH₃)₂ · 4H₂O, H₂hpac and imidazole in 1 : 1 : 1 mole ratio and characterized by elemental analysis, IR, ¹H NMR spectroscopy. An X-ray structure determination of the complex has been completed. In the solid state, a one-dimensional assembly of the [Ni(hpac)(Himdz)] molecules is formed via intermolecular hydrogen bonds between the imidazole N–H groups and the coordinated hydroxyphenyl-O atoms.     

Tetraaqua(4,4′‐dimethyl‐2,2′‐bipyridine‐κ2N,N′)nickel(II) sulfate monohydrate: a simple molecule with an extremely complex hydrogen‐bonding scheme

The title ionic compound, [Ni(C₁₂H₁₂N₂)(H₂O)₄]SO₄·H₂O, is composed of an Ni^II cation coordinated by a chelating 4,4′‐dimethyl‐2,2′‐bipyridine ligand via its two N atoms [mean Ni—N = 2.056 (2) Å] and by four aqua ligands [mean Ni—O = 2.073 (9) Å], the net charge being balanced by an external sulfate anion. The whole structure is stabilized by a solvent water molecule. Even though the individual constituents are rather featureless, they generate an extremely complex supramolecular structure consisting of a central hydrogen‐bonded two‐dimensional hydrophilic nucleus made up of complex cations, sulfate anions and coordinated and solvent water molecules, with pendant hydrophobic 4,4′‐dimethyl‐2,2′‐bipyridine ligands which interact laterally with their neighbours viaπ–π interactions. The structure is compared with closely related analogues in the literature.     

Crystal structure and magnetic properties of a thiocyanato-bridged dinuclear Cr(III)Cu(II) complex [(HL)Cu(SCN)Cr(NCS)3(NH3)2]·DMF

The complex [(HL)Cu(SCN)Cr(NCS)₃(NH₃)₂]·DMF [H₂L=3,3′-trimethylenedinitrilobis(2-butanoneoxime), DMF=N,N′-dimethylformamide] has been synthesized and the structure determined by single-crystal X-ray diffraction. The structure consists of a dinuclear thiocyanato-bridged Cr(III)Cu(II) unit and a DMF molecule as crystal solvate. The chromium ion is six-coordinated with two NH₃ molecules in axial positions and four nitrogen atoms, from four NCS⁻, in equatorial positions. One of the NCS⁻ bridges the Cr and Cu ions, the S atom of which occupies the apex of the square-pyramidal coordination at Cu with the tetradentate HL ligand in the basal site. Cryomagnetic measurement revealed a weak antiferromagnetic coupling between the heterometal ions with J=−0.63 cm⁻¹ based on the spin Hamiltonian H=−2JS₁S₂.     

Synthesis and structural characterization of a novel tetranuclear Cu(II) complex: [Cu<Subscript>4</Subscript>L<Subscript>2</Subscript>(pic)<Subscript>4</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>]·2H<Subscript>2</Subscript>O

A novel Salen-type bisoxime ligand, 6,6′-dimethoxy-2,2′-[(1,4-butylene)dioxybis(nitrilomethylidyne)]diphenol (H₂L) and its tetranuclear Cu(II) complex, [Cu₄L₂(pic)₄(H₂O)₂]·2H₂O, have been synthesized and characterized by elemental analyses, IR, TG-DTA and ¹H-NMR etc. The X-ray crystal structure of the complex reveals that formation of a tetranuclear structure, which consists of four copper(II) atoms, two pentadentate L²⁻units, four picratols, two coordinated water molecules and two crystallizing water molecules. Around four copper ions are all octahedral geometries. It was demonstrated that the picratols in the tetranuclear copper(II) complex show a novel tridentate coordination mode.     

Synthesis and crystal structure of bis{(μ-chloro)-chloro-[N-benzoyl-N′-(2-hydroxyethyl)thiourea] mercury(II)}

The complex bis{(µ-chloro)-chloro-[N-benzoyl-N′-(2-hydroxyethyl)thiourea] mercury(II)} was prepared by reaction of HgCl₂ with N-benzoyl-N′-(2-hydroxyethyl) thiourea(HL). The compound was characterized by IR and ¹H?NMR spectroscopy and its structure was determined by single crystal X-ray diffraction. The complex is binuclear with two Hg(II) ions tetrahedrally coordinated by a terminal chloride, two bridging chlorides and a HL molecule. The Hg(II) ion is coordinated with HL via S(1).