The first anion template cubic cyanometallate cage and its 3,5-dimethyltris(pyrazolyl)methane iron(II, III) tricyanide building blocks

Several 3,5-dimethyltris(pyrazolyl)methane iron(II, III) tricyanide building units have been prepared and characterized. Treatment of K[(HC(3,5-Me₂Pz)₃)Fe^II(CN)₂](K⁺1^-) with Fe^II(H²O)⁶(BF⁴)² affords a new anion template cubic cyanometallate cage [(BF₄) ⊂ {Fe^II(H₂O)}₄{(HC(3,5-Me₂Pz)₃)Fe^II (CN)₃}₄](BF₄)³ 3.     

One- and Two-Dimensional Cadmium(II) Tetracyanonickelate(II) Coordination Polymers With Imidazole and 2-Methylimidazole Ligands

Two novel cyano-bridged heteropolynuclear complexes, [Cd(im)₄Ni(μ-CN)₂(CN)₂] _n (1) and [Cd(mim)₂Ni(μ-CN)₄] _n (2) (im: imidazole and mim: 2-methylimidazole), have been synthesized and characterized. In 1, the trans-directed cyanide ligands of [Ni(CN)₄]²⁻ anions link two [Cd(im)₄]²⁺ units, whereas in 2, all the cyanide groups take part in bonding with two adjacent [Cd(mim)₂]²⁺ units, resulting 1D and 2D coordination polymers, respectively. The coordination environment of the Cd(II) ion described as distorted octahedral geometry, whereas around the Ni(II) centre had square planar geometry in both complexes. The crystals packing of 1 and 2 were a composite of hydrogen bonding, π···π and C–H···Ni interactions.     

Synthesis, crystal structure and luminescent properties of a thiocyanato bridged two-dimensional heteronuclear polymeric complex of cadmium(II) and copper(II)

A novel heteronuclear polymeric complex Cd(SCN)₃Cu(en)₂NO₃ (1) (en = ethylenediamine) has been synthesized and structurally characterized. The Cd(II) atom is surrounded by three S atoms and three N atoms from four 1,3-μ-SCN⁻ and two 1,1,3-μ-SCN⁻ to attain a distorted octahedral coordination geometry. Six Cd(II) centers are linked by twelve thiocyanato bridges to form hexagonal metallocyclic unit [Cd₆(SCN)₁₂] and extend a 2D network. Moreover, a 1,1,3-μ-SCN⁻ links two cadmium and one copper metal atoms. The luminescent properties of 1 in the solid state were investigated.     

Tris(μ-phenoxo) bridged Cd(II) polymer synthesised from a symmetrical tripodal ligand: A novel observation for heptadentate monocapped trigonal antiprismatic Schiff base complex

A novel one-dimensional cadmium(II) polymer [Cd₂(L){HCON(CH₃)₂}N(CN)₂]_n (H₃L = condensation product of tris(2-aminoethyl)amine and salicylaldehyde) has been achieved from a tripodal Schiff base tris[(2-salicylaldeneimino)ethyl]amine or ‘trensal’. The structure confirmed from single crystal X-ray diffraction analysis reveals that each of the tris(μ-phenoxo) bridged individual Cd(II) dimeric units is interlinked via μ-(1,5) end-to-end (EE) dicyanamide [N(CN)₂]⁻ ligand framing a wavy chain polymer, which is believed to be the first report of its kind in the literature.     

Comparison of 1-hydroxymethyl-3,5-dimethylpyrazole and 1-benzyl-2-hydroxymethylimidazole coordination properties towards copper(II)

Using 1-hydroxymethyl-3,5-dimethylpyrazole as the starting ligand and 2-propanol as the solvent and a molar ratio Cu:L, 1:4, a dinuclear Cu(II) complex has been obtained. The microanalytical data and the crystal structure reveal that the dicopper complex with two bridging methoxide groups contains the 3,5DMePz, 1-CH₂O-3,5DMePz and BF₄⁻ ligands which are received during the coordination process. The compound shows an antiferromagnetic intramolecular interaction between the Cu(II) ions.     

Cadmium(II)-N-Ethylimidazole Coordination Polymer via Different Coordination Environment and Chloro Bridges: Synthesis, X-ray Structure, Spectroscopic and Thermal Analysis

A novel coordination polymer [Cd₂(μ-Cl)₄(Neim)₃]_n (1) (Neim = N-ethylimidazole) was synthesized and structurally characterized by means of elemental analysis, thermal analysis, FT-IR spectrum and single-crystal X-ray diffraction. There are two different cadmium centers in 1. One of these metal centers has octahedral geometry, while the other has square pyramidal geometry. Two Neim ligands are coordinated to the Cd(II) ion in octahedral geometry while one Neim ligand is coordinated to the Cd(II) ion in square pyramidal geometry. Relatively weak C–H···Cl interactions between N-ethylimidazole molecules and chloro ions in the complex play an important role in the construction of a three-dimensional supramolecular framework. Complex 1 exhibits photoluminescence emission in solid state at room temperature.     

Reactivity studies of 2,3,5,6-Tetra(2-pyridyl) pyrazine (tppz) with first-row transition metal ions

Reactions of 2,3,5,6-tetra(2-pyridyl) pyrazine (tppz) with [ML₆][X]₂ (L = CH₃CN, H₂O;X = [BF₄]⁻, [ClO₄]⁻, [NO₃]⁻ [BArF]⁻(BArF - B[3,5-C₆H₃(CF₃)₂]₄) lead to the high-yield formation of mononuclear [M(tppz)₂]²⁺, (M = Mn^II, Fe^II, Co^II, and Ni^II) and dinuclear [Ni₂(tppz)(CH₃CN)₆]⁴⁺ species. The new compounds were fully characterized by X-ray crystallographic, spectroscopic, and magnetic susceptibility measurements. Surprisingly, the 2:1 M:tppz reactions did not lead to isolation of the dinuclear species except in the case of Ni(II). It was further noted that even in the case of the Ni reactions, the nuclearity of the product depends on the choice of anions and the reaction conditions. Magnetic measurements of the mononuclear species [Co(tppz)₂]²⁺ revealed thermally induced spin-crossover behavior from a high-spin S = 3/2 at higher temperatures to a low-spin S = 1/2 complex at lower temperatures. The dinuclear compound [Ni₂(tppz)(CH₃CN)₆]⁴⁺ exhibits a weak anti-ferromagnetic interaction through the bridging tppz ligand.     

Synthesis,Crystal Structures and Fluorescent Properties of Two Bimetallic Coordination Polymers

Two novel 2D and 3D bimetallic Cd^IINi^II coordination polymers, Cd(2Mpz)(H₂O)Ni(CN)₄ (I) (2Mpz: 2-methylpyrazine) and Cd(2Epz)(H₂O)Ni(CN)₄ (II) (2Epz: 2-ethylpyrazine), have been synthesized and characterized by elemental analysis, powder X-ray diffraction, IR spectra, fluorescent spectra, single crystal X-ray diffraction and thermogravimetric analysis. Based on the analysis of structures, it can be found that the Cd(II) ions in the two complexes have the similar octahedral coordination geometry of CdN₅O, which are linked by [Ni(CN)₄]²⁻ units at the equatorial plane to form 2D sheet layers [CdNi(CN)₄] _n . However, it’s noted that the coordination environment of Ni(II) ions and action of ligands are different. All the Ni(II) ions in I are the five-coordinated pentahedron configuration and 2-methylpyrazine acts as a bridging ligand linking the Cd(II) and Ni(II) ions of the adjacent layers, leading to the 3D metal–organic framework. The structure of II indicates all the Ni(II) ions are the four-coordinated square plane and 2-ethylpyrazine is a terminal ligand coordinated to Cd(II) ions, forming the 2D layer structure. Moreover, the two complexes display significant thermal stability and fluorescent properties.     

Structure and chemical properties of a copper(II) hydrazido complex: [{Cu(HB(3,5-iPr2pz)3)}2(μ-NCOOEt)2]

The novel copper(II) hydrazido(2?) complex ligated by hydrotris(pyrazolyl)borate was synthesized to obtain insight into the copper coordination chemistry in the presence of diazene and hydrazine ligands. The structure of [{Cu(L1)}₂(μ-NCOOEt)₂] was determined by X-ray crystallography, where L1 = hydrotris(3,5-diisopropyl-1-pyrazolyl)borate anion, and along with spectroscopic characterization, e.g. UV–Vis and ESR, prove the presence of copper(II) centers.     

Coordination versatility of 1,5-bis(salicylidene)carbohydrazide in Ni(II) complexes

Versatile coordination behavior of a polydentate Schiff base ligand 1,5-bis(salicylidene)carbohydrazide (H₃bsc) has been explored in Ni(II) complexes. [Ni(H₃bsc)₂](ClO₄)₂ (1)·H₂O·3CH₃CN is a bis chelate mononuclear complex of H₃bsc in keto form, and [Ni₄(H_0.5bsc)₂(O₂CCMe₃)₃(CH₃OH)₄](2)·2H₂O·2CH₃OH is a tetranuclear complex of H₃bsc with an unusual coordination. In 2, one phenolate group of the ligand coordinates in a monodentate way and the other coordinates in a μ₂-bridging mode to the Ni(II) center. This unusual coordination mode of the ligand stabilizes the Ni(II) complex in a tetranuclear form where the carbonyl oxygen of the ligand exists in between keto and enol form of bond order 1.5. Thus, complex 2, represents an unprecedented coordination behavior of the Schiff base ligand derived from carbohydrazides. Studies of magnetic properties of 2 are reported which reveal antiferromagnetic interaction between four Ni(II) centers.     

Anion-directed assembly of two fluorescent Cd(II) coordination polymers with a versatile multidentate N-donor building block 3-(2-pyridyl)-4,5-bis(4-pyridyl)-1,2,4-triazole

Assembly of Cd(II) nitrate with a novel tripyridyltriazole building block 3-(2-pyridyl)-4,5-bis(4-pyridyl)-1,2,4-triazole (L¹) and pseudohalide anion dicyanamide (dca) or azide (N₃) yields two coordination polymers {[Cd(L¹)₂(dca)₂](H₂O)₂}_n (1) and {[Cd₂(L¹)(μ_1,1-N₃)₂(μ_1,3-N₃)(N₃)](H₂O)_1.5}_n (2). Single crystal X-ray diffraction analysis indicates that the Cd(II) centers in 1 are bridged by the bidentate L¹ ligands to form 1D arrays, which are further extended to a 3D network via hydrogen bonding and aromatic stacking. Significantly, the L¹ ligands in 2 display the unusual pentadentate coordination and the azide anions take different μ_1,1-, μ_1,3-, and unidentate binding modes, interlinking the Cd(II) ions to afford a complicated 3D open framework with the inclusion of lattice water guests. Both complexes exhibit strong solid state fluorescent emissions at room temperature.     

The first example of half-sandwich cobalt(III) complex with hydrotris(pyrazolyl)borate ligand

This paper presents the synthesis, crystal structure and spectroscopic properties of a novel half-sandwich mononuclear cobalt(III) complex with hydrotris(3,5-dimethylpyrazolyl)borate ligand and thiocyanate [Tp^*Co(Hpz^*)(NCS)₂]·H₂O·CH₃OH (Tp^*: hydrotris(3,5-dimethyl- pyrazolyl)borate, Hpz^*: 3,5-dimethylpyrazole). The structure was determined by X-ray diffraction. The complex crystallizes in the monoclinic system, space group C_c, a=18.591(6) Å, b=10.536(3) Å, c=17.568(5) Å, β=11.284(5)°, Z=4, R₁=0.0501, wR₂=0.1179. The cobalt(III) ion in the complex is six-coordinated with nitrogen atoms, three from Tp^*, two from pyrazole and two from two thiocyanates, to form octahedral environment. The hydrogen atoms of O(2) of water molecule are connected by hydrogen bonds with S atoms of two adjacent complex molecules to form 1-D chains. The hydrogen atom of N(8) of complex molecule is connected by hydrogen bond with methanol. The spectroscopic results are consistent with the crystallographic study.     

Simultaneous novel synthesis of conducting and non-conducting halogenated polymers by electroinitiation of (2,4,6-trichloro- or 2,6-dichlorophenolato)Ni(II) complexes

NiL₂(Ph)₂·xH₂O [L=3,5-dimethylpyrazole or N-methyl imidazole; Ph=DCP or TCP; x=0, 1 or 3] complexes were synthesised and characterised by analytical and spectroscopic methods using elemental analysis and FTIR. The electrochemical behavior of the complexes was studied by cyclic voltammetry in tetrabutylammoniumtetrafluoroborate-N,N-dimethylformamide electrolyte-solvent couple. Cyclic voltammogram of the complexes displayed two-step oxidation processes under the nitrogen gas atmosphere. The polymerization of the complexes was accomplished in the same solvent-electrolyte couple by the constant potential electrolysis of NiL₂(Ph)₂·xH₂O, synthesizing the poly(di- or monochlorophenylene oxide)s via free radical mechanism. The simultaneous polymerization of non-conducting polymer and conducting polymer (the conductivity of 0.7 S cm⁻²) were achieved by electroinitiated polymerization of Ni(DMPz)₂(TCP)₂. The structural analysis of the polymers were performed using FTIR, ¹H NMR and ¹³C NMR spectroscopic techniques and DSC for the thermal analysis. The kinetics of the polymerization was followed by in situ UV-vis spectrophotometer during the electrolysis. The low temperature ESR spectrum of the electrolysis solution also confirmed the formation of phenol radical (g=2.0028). One electron oxidation process of NiL₂(DCP)₂·xH₂O produces a new Ni(II) complex, Ni(L-L)(DCP)₂(S) by the rapid decomposition of Ni^IIIL₂(DCP)₂ into a ligand radical producing a singlet with the g value of 2.0015. Second electron oxidation process generates oligemers, which could not be isolated from the electrolyte solution.     

Binuclear cyano-bridged complex derived from [MnIII(salpn)] and [FeIII(CN)6]: Synthesis,structure and magnetic properties

The reaction of the neutral [Mn(salpn)C(CN)₃(H₂O)] (salpn^2 − = N,N^′-1,3-propylenebis(salicylideneiminato) dianion) with [Fe^III(CN)₆]^3 − in the presence of strong oxidizer (NH₄)₂S₂O₈ yields a binuclear anion complex [NH₃CH₂CH₂CH₂NH₃]^2 +{[Mn^III(salpn)(H₂O)][Fe^III(CN)₆]}^2 − (1). Its structure, DC and AC susceptibility have been studied. Frequency dependence of the AC susceptibility characteristic for single-molecule magnets has been found.     

First dicadmium(II) complex of tripodal amide ligand with one edge-sharing monocapped octahedral geometry

A new dicadmium(II) complex [Cd₂(L)₂(H₂O)₂](NO₃)₄ · 8H₂O (1) with the tripodal amide ligand L (tris[3-aza-2-oxo-4-(2-pyridyl)butyl]amine) was synthesized and structurally characterized. Complex 1 is revealed as a dinuclear 2:2 (Cd:L) complex, in which each cadmium(II) ion is hepta-coordinated with the coordination surrounding of distorted monocapped octahedral geometry. Two cadmium(II) ions are dibridged by two carbonyl μ-O atoms forming a Cd₂(μ-O)₂ parallelogram-type moiety. Interestingly, the dinuclear coordination sphere can be seen as resulting from the fusion of two distorted monocapped octahedral [Cd(L)(H₂O)]²⁺ units through sharing one edge originated from the two carbonyl μ-O atoms as a first example. Comparative NMR, IR and FAB-mass data of 1 are also discussed.     

Stability constants of adipate complexes of copper(II), nickel(II), zinc(II), cobalt(II), uranyl(II) and thorium(IV) determined by electrophoresis

Stability constants of Copper(II), Nickel(II), Cobalt(II), Zinc(II), Uranyl(II) and Thorium(IV) adipates have been determined by paper electrophoresis. Adipic acid (0.005 mol dm^?3) was added to the background electrolyte: 0.1 mol dm^?3 HClO₄. The proportions of (CH₂)₄COOH COO^? and (CH₂)₄C₂O⁼₂ were varied by changing the pH of the electrolyte. These anions yielded the complexes Zn(CH₂)₄COOH COO⁺, Co(CH₂)₄COOH COO⁺, Ni(CH₂)₄COOH COO⁺, Th(CH₂)₄COOH COO³⁺, Th[(CH₂)₄COOH COO]₄, Cu(CH₂)₄ C₂O₄ and UO₂[(CH₂)₄(C₂O₄)]^2?₂, whose stability constants are found to be 10^2.8, 10^2.8, 10^3.2, 10^5.2, 10^15.3, 10^2.7 and 10^11.8 respectively (μ = 0.1, temp. 40°C).     

Synthesis and crystal structure of scandium(III) and cadmium(II) thiocyanato complexes with dimethylsulfoxide

Two novel complex compounds, molecular fac-[Sc(NCS)₃(DMSO)₃] and polymeric chain [Cd(NCS)_4/2(DMSO)₂]_∞ (DMSO = dimethylsulfoxide), were synthesized and structurally characterized. In both complexes, the metal atoms have octahedral coordination with the NCS⁻ ion serving two different functions: as a terminal ion with the coordination via N in Sc complex and as a bridge ligand with the coordination via N and S in the case of Cd compound, respectively. The DMSO ligands are coordinated by oxygen atoms.     

Highly active and stereospecific polymerizations of 1,3-butadiene by using bis(benzimidazolyl)amine ligands derived Co(II) complexes in combination with ethylaluminum sesquichloride

A family of cobalt(II) complexes supported on tridentate dibenzimidazolyl ligands having a general formula: [N(CH₃)(CH₂)₂(Bm-R)₂]CoCl₂ (where Bm = benzimidazolyl, R = H; -Me; -Bz), have been prepared by the condensation of o-phenylene diamine with methyliminodiacetic acid. The Co(II) complexes exhibited high activities for the polymerization of 1,3-butadiene, on activation with ethylaluminum sesquichloride (EASC), to yield predominantly cis-1,4 microstructure. The polymers are characterized by high molecular weight with polydispersity values between 2.35 and 3.37. The ligand modification shows remarkable influence on polymerization activity. The stereospecificity of the catalysts is consistent for a wide range of reaction conditions, except temperature. The electronic influence of ligand structure towards metal center is investigated by using cyclic voltammetric analysis and the generation of cationic active centers is identified via UV-vis spectroscopic analysis of the catalyst system.     

Cobalt(II), Zinc(II) and Cadmium(II)-Squarate Complexes with N-Methylimidazole

Three M(II)-squarate complexes, [Co(sq)(H₂O)(Nmim)₄] (1), [Zn(μ_1,3-sq)(H₂O)₂ (Nmim)₂] _n (2) and [Cd(μ_1,3-sq)(H₂O)₂(Nmim)₂] _n (3) (sq = squarate, Nmim = N-methylimidazole) have been synthesized and characterized by elemental, spectral (IR and UV–Vis.) and thermal analyses. The molecular structures of the complexes have been investigated by single crystal X-ray diffraction technique. The squarate ligand acts as two different coordination modes as a monodentate (in 1) and bis(monodentate) (O ^1– O ³ ) bridging ligand (in 2, 3). The Co(II) atom has a distorted octahedral geometry with the basal plane comprised of three nitrogen atoms of Nmim ligands and a oxygen atom of squarate ligand. The axial position is occupied by a nitrogen atom of Nmim and one aqua ligand. The crystallographic analysis reveals that the crystal structures of 2 and 3 are one-dimensional linear chain polymers along the c and b axis, respectively. The configuration around each metal(II) ions are distorted octahedral geometry with two nitrogen atoms of trans-Nmim, two aqua ligands and two oxygen atoms of squarate-O¹,O³ ligand. These chains are held together by the C–H···π, π···π and hydrogen-bonding interactions, forming three-dimensional network.     

Coordinate chloride and water-assisted assembly of novel 3D-cageworks of cadmium(II) complex with 4-[N,N-bis(2-cyanoethyl)]aminopyridine

Synthesis and structure of the cadmium(II) complex of [Cd^II(CEAP)₂(H₂O)(CH₃COO)Cl] {CEAP = 4-[N,N-bis(2-cyanoethyl)]aminopyridine} has been reported. The structure exhibits a novel 3D-cagework assembly with the assistance of the coordinated chloride anion and water molecule via forming multiple hydrogen bonds with the cyanoethyl arms of CEAP.