Crystal structure of a μ-oxo-bridged dimeric iron(III) complex

A dimeric [{Fe(5-ClL1)}₂(μ-O)], [H₂-5-ClL1 = N,N′-bis(5-chloro-2-hydroxybenzylidene)-2-methylpropane-1,2-diamine] tetradentate Schiff-base complex, 1, has been synthesized and its crystal structure has been determined by single crystal X-ray diffraction analysis. Structural analysis of complex 1 shows that the complex is a centrosymmetric dimer. Each of the Fe(III) ions has a five-coordinate geometry and one oxygen atom bridges two Fe(III) ions to form a μ-oxo structure. The geometry around iron atom can be described as a square based pyramid with the FeN₂O₂ coordination plane and oxo ligand.     

Synthesis and characterization of a monomeric and a dihydroxo-bridged dimeric complexes of iron(III) with α-benzoinoxime

The reaction of α-benzoinoxime, H₂BNO with FeCl₃ in the presence of Et₃N as a base gives the mononuclear Fe(III) complex, Fe(HBNO)₃ (1). Treatment of 1 with a methanolic solution of KOH at room temperature leads to a dinuclear Fe(III)–Fe(III) complex, [Fe(HBNO)₂OH]₂ (2). The complexes were initially characterized on the basis of their elemental, mass and thermal analyses. The IR studies were useful in assigning the coordination mode of the benzoinoxime ligand to the iron metal. In addition, the presence of a hydroxo-bridge in the dimeric complex 2 is inferred from the IR spectral studies. Room-temperature Mössbauer studies indicated octahedral, high-spin iron(III). Variable-temperature magnetic susceptibility measurements supported the existence of the μ-dihydroxo-bridging structure core, Fe^III(μ-OH)₂Fe^III in the dinuclear complex 2. Theoretical modelling of the magnetic data indicated a weak antiferromagnetic spin exchange between the iron(III) centers (J = −8.35 cm⁻¹, g = 2.01, ρ = 0.02 and TIP = 1.7 × 10⁻⁴ cm³ mol⁻¹ for H = −2JS₁ · S₂). The electronic spectra of the complexes revealed two bands due to d–d transitions and one band assignable to an oxygen (p_π) → Fe(d_π∗) LMCT transition observed in each complex. An additional charge-transfer transition, assignable to μ-hydroxo(p_π) → Fe(d_π∗), was observed for the dimeric complex 2. The structural and vibrational behaviors of these complexes have been elucidated with quantum mechanical methods.     

Coordination chemistry of 1,4-bis(carboxymethyl)-1,4,7-triazacyclononane: Synthesis and characterization of mononuclear and binuclear μ-oxo-bridged iron(III) complexes,and a 1D-helical copper(II) chain

The syntheses of the pentadentate ligand 1,4-bis(carboxymethyl)-1,4,7-triazacyclononane (LH₂) and its use in the preparation of [LHCu]ClO₄ (1), and a mononuclear iron(III) complex ([LFeCl] (2)) are reported. The hydrolysis of 2 in the presence of an excess of NaClO₄ resulted in the crystallization of a binuclear complex, [Fe₂(μ-O)L₂] · (NaClO₄)₃ · CH₃OH · 3H₂O (3). The crystal structures of 1–3 have been determined by single-crystal X-ray crystallography. In complex 1, the Cu(II) centre is in square based pyramidal environment, with two nitrogen atoms from the tacn ring and two oxygen atoms from two different carboxylate groups lying in the basal plane and the third nitrogen atom occupying the apical position. One pendant acetic acid group is protonated and, instead of coordinating to the copper(II) centre, participates in hydrogen bonding interactions with the perchlorate counter-ion. The coordinated carboxylate group forms a bridge to the copper atom of an adjacent [LHCu]⁺ molecule, thus generating 1D-helical chains. The compound exhibits weak ferromagnetic coupling probably due to weak interactions between [LHCu]⁺ molecules. In complex 2, the iron(III) centre is in a distorted octahedral geometry, with the fac-coordinated triamine ring, two carboxylate groups and one chloride ligand occupying the coordination sphere. In the binuclear complex 3, two iron(III) centres are bridged by one oxygen atom to form a μ-oxo-diiron(III) complex with an Fe?Fe distance of 3.423(3) Å and a non-linear Fe–O–Fe angle of 144.4°. This binuclear complex features strong antiferromagnetic coupling between the two iron(III) centres.     

Silver(I) bromide complexes of the rigid diphosphanes 1,2-bis(diphenylphosphano)benzene (dppbz) and 4,5-bis(diphenylphosphano)-9,9-dimethyl-xanthene (xantphos): Crystal structures of [Ag(μ2-Br)(dppbz)]2, [AgBr(xantphos)] and [AgBr(xantphos)(py2SH)]

Reaction of silver(I) bromide with equimolar amounts of the rigid diphos ligands 1,2-bis(diphenylphosphano)benzene (dppbz) and 4,5-bis(diphenylphosphano)-9,9-dimethyl-xanthene (xantphos) in acetone and acetonitrile led to the corresponding chelates [Ag(μ₂-Br)(dppbz)]₂ (1) and [AgBr(xantphos)] (2). Treatment of 1 and 2 with pyridine-2-thione (py2SH) in ethanol gave the mixed-ligand complexes [AgBr(dppbz)(py2SH)] (3) and [AgBr(xantphos)(py2SH)] (4), respectively. Compounds 1, 2 and 4 have been characterized by X-ray diffraction, establishing distorted tetrahedral or trigonal planar coordination geometries of the silver atoms.     

Voltammetric and titrimetric study of acid-base properties of some μ-oxo dimeric iron(III) complexes inDMF

Summary The acid-base properties of the -oxo bridged dimeric iron complexes [FeL]₂O with the ligands based on S-alkyl-1,4-bis(substituted salicylidene)isothiosemicarbazide and a tetramer with S-methyl-1,4-bis(salicylidene)isothiosemicarbazide, {[FeL]₂O}₂I₃·I₂, were investigated by cyclic voltammetry at glassy carbon electrode inDMF. Studies were carried out in the presence of either a weak (phenol) or a strong (HClO₄ aq.) acid. The stoichimoetry of the reaction, changes in the general voltammetric pattern and the electrode reaction mechanism were discussed. These studies served as the basis for three-electrode amperometric titrations to determine the content of several of these complexes.

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Voltammetrische und titrimetrische Untersuchung der Säure-Base-Eigenschaften einiger -oxo dimerer Eisen(III)-Komplexe inDMF-Lösungen

Zusammenfassung Die Säure-Base-Eigenschaften einiger dimerer -oxo-Eisen(III)-Komplexe [FeL]₂O mit Liganden auf Basis von 1,4-bis(substituierten Salicyliden)S-(alkyl)isothiosemicarbaziden sowie eines tetrameren Komplexes mit 1,4-Bis(salicyliden)S-methylisothiosemicarbazid, {[FeL]₂O}₂I₃·I₂, wurden mittels zyklischer Voltammetrie an der Glaskohlenstoffelektrode inDMF-Lösungen untersucht. Die Messungen wurden in Gegenwart entweder einer schwachen (Phenol) oder einer starken (HClO₄ aq.) Säure ausgeführt. Die Stöchiometrie der Reaktion, die Änderungen der voltammetrischen Kurven und der Elektroden-Reaktionsmechanismus wurden diskutiert. Diese Untersuchungen stellten eine Basis für Drei-Elektroden amperometrische Titrationen dar, die für die Bestimmung des Gehalts einiger dieser Komplexe angewendet wurden.

     

Synthesis and structures of 4,5-dimethyl-1,3-bis(pyridin-2-ylmethyl)-1H-imidazolium chloride and 1,1′-bis(pyridin-2-ylmethyl)-2,2′-bis(4,5-dimethylimidazole)

4,5-Dimethyl-1,3-bis(pyridin-2-ylmethyl)-1H-imidazolium chloride (1) was synthesized and characterized by IR and NMR spectroscopy and X-ray diffraction. An attempt to prepare the free tridentate N-heterocyclic carbene pincer ligand by the reaction of 1 with KN(SiMe₃)₂ resulted in the formation of 1,1′-bis(pyridin-2-ylmethyl)-2,2′-bis(4,5-dimethylimidazole) as a product of dimerization of the target carbene followed by the rearrangement accompanied by the elimination of dipyridylethane.

     

Complexes of divalent transition metal chlorides with the tetradentate Schiff base ligand 1,2-bis(2′-pyridylmethyleneimino)-benzene

Summary Transition metal(II) chloro complexes of the new Schiff base ligand 1,2-bis(2-pyridylmethyleneimino)benzene (L), derived from 2-pyridinecarboxaldehyde and 1,2-phenylenediamine, were prepared. Compounds of [MnLCl₂]-H₂O, [CoLCl₂]·2H₂O, [NiLCl₂] and [Zn₃L₂Cl₄]Cl₂ were prepared. Details are given of the formation of the complex [Cu(L·EtOH)Cl₂], in which one molecule of EtOH adds across only one of the Schiff base {ie531-01} groups to give the coordinated ligand L·EtOH. The rationalization of this type of reaction by considering the steric requirements of the ligand is given. The complexes were characterized by elemental analyses, conductivity measurements, thermal techniques, mass spectra, magnetic susceptibilities and spectroscopic (i.r., ligand field, e.s.r., ¹H n.m.r.) studies. The nitrogen donor atoms of the tetradentate ligands L and L·EtOH are assumed to adopt an essentially planar arrangement about manganese(II), cobalt(II), nickel(II) and copper(II), with the remaining axial coordination sites occupied by chloro ligands to yield high-spin octahedral molecules. A trinuclear structure, based on tetrahedrally coordinated metal ions, is proposed for the zinc(II) complex.     

Structure and Photosynthetic Mimicking of Bis(2,6-bis(benzimidazol-2-yl)pyridine)manganese(II)

Introduction　　Manganeseionsplayanimportantroleinthelight in ducedoxidationofwatertomolecularoxygeninphotosys temII (PSII)ofgreenplants.1 3Inrecentyears ,man ganesecomplexesofpolypyridineligands ,suchasbipyri dine ,1,10 phenanthrolineand 2 ,2′:6′,2″ terpyridine ,havehadconsiderableattentionasthecomplexesformedareusefulmodelsformanganese containingbimolecu lars .4 6 Therefore ,synthesisandcharacterizationofman ganeseinitsvariousoxidationstates ,withvariousligandtypesandnuclearities ,hav…     

Crystal structure and thermal stability of A μ1,1-(OMe)-bridged dimeric Schiff base iron(III) complex

A new μ_1,1-OMe-bridged dimeric iron(III) complex, [Fe₂L₂(μ_1,1-OMe)₂(NCS)₂], where L is the deprotonated form of 2-[(2-ethylaminoethylimino)methyl]-5-methoxyphenol, has been prepared and structural characterized by elemental analysis, IR spectrum, and single crystal X-ray crystallography. The complex crystallizes in the monoclinic space group P2₁/c, with unit cell dimensions a = 10.156(1) Å, b = 11.972(1) Å, c = 14.256(2) Å, β = 102.643(3)°, V = 1691.3(3) ų, Z = 2, R ₁ = 0.0394, and wR ₂ = 0.0922. Each Fe atom in the complex is in an octahedral coordination. The Fe...Fe distance is 3.102(1) Å. The thermal stability of the complex was studied.     

Synthesis and Structure of a Novel Ion-pair Palladium(Ⅱ) Compound Containing 2-Thioxo-1,3-dithiole-4,5-bis(thiolate)

A novel ion-pair palladium(Ⅱ) compound,(NO2BzPy)2[Pd(dmit)2](NO2BzPy+ = 1-(4-nitrobenzyl)pyridinium,dmit2-= 2-thioxo-1,3-dithiole-4,5-bis(thiolate)),was synthesized and characterized by single-crystal X-ray structure determination.This compound crystallizes in the monoclinic system,space group P21/n with a = 10.4463(11),b = 8.5627(9),c = 20.017(2) ,β = 97.7730(10)°,V = 1774.1(3) 3,Z = 2,C30H22N4O4S10Pd,Mr = 929.52,Dc = 1.740 g/cm3,μ = 1.155 mm-1,S = 1.006,F(000) = 936,R = 0.0354 and wR = 0.0675.The most intriguing general structural feature of the compound is the completely segregated columnar stacks of anions and cations.There exist hydrogen-bonding interactions within the cation column.     

Synthesis and reactivity of an isolable cobalt(I) complex containing a β-diketiminate-based acyclic tetradentate ligand

A model for cobalamin was synthesized using a new monoanionic tetradentate nitrogen donor ligand; 2-(4-tolyl)-1,3-bis(2-isopropylpyridyl)propenediimine (Tol-BDI((2-pp)2)H) (1), which utilizes isopropylpyridines as pendant arms on a β-diketiminate (BDI) backbone. During the synthesis of 1, the rearrangement product, Tol-BDI((2-pp)(4-pp))H (2) was observed. Metalation of 1 with zinc iodide and cobalt chloride yielded the corresponding Tol-BDI((2-pp)2)ZnI (3) and Tol-BDI((2-pp)2)CoCl (4) complexes. The redox properties of 4 in comparison to cobalamin were examined through electrochemical studies. Electrochemical and bulk reduction of complex 4 gave a diamagnetic cobalt(I) complex, Tol-BDI((2-pp)2)Co (5). Reactivity of 5 toward C-X bonds was investigated using methyl iodide and 1-iodo-2-(trimethylsilyl)acetylene, yielding Tol-BDI((2-pp)2)Co(CH(3))I and Tol-BDI((2-pp)2)Co(C(2)Si(CH(3))(3))I respectively. Synthesis and characterization details for these complexes, including the crystal structure of 3, are reported.     

Sorption of benzene vapors to flexible metal–organic framework [Zn2(bdc)2(dabco)]

The isotherms of benzene sorption by the metal–organic coordination polymer [Zn₂(bdc)₂(dabco)] were studied within the temperature range 25–90 °C at pressures up to 75 torr. The maximal benzene content in [Zn₂(bdc)₂(dabco)] at room temperature was demonstrated to correspond to the composition [Zn₂(bdc)₂(dabco)]·3.8C₆H₆. It was established that the process of benzene desorption from the substance under investigation occurs in three stages. (1) Evaporation of benzene from the phase of variable composition (phase C) with compression and distortion of the unit cell (the composition of the phase C varies from [Zn₂(bdc)₂(dabco)]·3.8C₆H₆ to [Zn₂(bdc)₂(dabco)]·3.2C₆H₆). (2) The transformation of the phase C into phase P. The phase P has the same unit cell geometry as that for the empty framework. The maximal benzene content is [Zn₂(bdc)₂(dabco)]·1.0C₆H₆. (3) Benzene evaporation from the phase P of variable composition. We studied the temperature dependences of the equilibrium vapor pressure of benzene for the samples with compositions [Zn₂(bdc)₂(dabco)]·3.0(3)C₆H₆ and [Zn₂(bdc)₂(dabco)]·2.0(3)C₆H₆ within the temperature range 290–370 K. The thermodynamic parameters of benzene vaporization were determined for the latter compound ( $ \Updelta {\text{H}}_{{{\text{av}} .}}^{o} = 49\left( 1 \right) \,{\text{kJ }}\left( {{\text{moleC}}_{6} {\text{H}}_{6} } \right)^{ - 1} $ ; $ \Updelta {\text{S}}_{{{\text{av}} .}}^{^\circ } = 100\left( 3 \right)\, {\text{J}}\left( {{\text{moleC}}_{6} {\text{H}}_{6} {\text{K}}} \right)^{ - 1} $ ; $ \Updelta {\text{G}}_{298}^{^\circ } = 19.0\left( 2 \right)\, {\text{kJ}}\left( {{\text{moleC}}_{6} {\text{H}}_{6} } \right)^{ - 1} $ ).     

Formation of the imide [Ta(NMe2)3(μ-NSiMe3)]2 through an unprecedented α-SiMe3 abstraction by an amide ligand

Ta(NMe(2))(4)[N(SiMe(3))(2)] (1) undergoes the elimination of Me(3)Si-NMe(2) (2), converting the -N(SiMe(3))(2) ligand to the ═NSiMe(3) ligand, to give the imide "Ta(NMe(2))(3)(═NSiMe(3))" (3) observed as its dimer 4. CyN═C═NCy captures 3 to yield guanidinates Ta(NMe(2))(3-n)(═NSiMe(3))[CyNC(NMe(2))NCy](n) [n = 1 (5), 2 (6)]. The kinetic study of α-SiMe(3) abstraction in 1 gives ΔH(?) = 21.3(1.0) kcal/mol and ΔS(?) = -17(2) eu.     

Synthesis,spectroscopy, magnetism and X-ray structure of μ-(bipyrimidine)-bis[aqua(bipyrimidine)(saccharinato)copper(II)] bis(saccharinate) tetrahydrate

The compound [Cu₂(bipym)₃(sac)₂(H₂O)₂](sac)₂(H₂O)₄ (bipym = 2,2-bipyrimidine and sac = saccharin) crystallizes in the space group P-1, with a = 10.710(3), b = 10.725(3), c = 13.637(5) Å, a = 70.07(3), = 80.31(2), g = 82.87(3)° and Z = 2. The geometry in the centrosymmetric dinuclear complex around each Cu^II ion is a distorted octahedron, in which the equatorial plane is formed by a nitrogen atom of a bis-didentate bridging bipym ligand, two nitrogen atoms of a didentate bipym ligand, and the nitrogen atom of a coordinating sac ligand. The axial positions in the octahedron are occupied by a second nitrogen of the bis-didentate bridging bipym ligand and a water molecule. The lattice contains two saccharinate anions and four water molecules held together in a hydrogen-bonded network. The i.r vibrations of the bipym ligand are found as a quasi-symmetric doublet at 1558 and 1580 cm^–1, while the most important i.r vibrations of the sac ligand are observed at 1629 and 1644 cm^–1 (carbonyl vibrations) and at 1285 and 1159 cm^–1 (sulfonyl vibrations). The magnetic exchange interactions between the Cu ions is very weak and is ferromagnetic (J < 0.1 cm^–1).     

Synthesis and magnetic interaction of μ-2-chloroterephthalato binuclear iron (Ⅱ) complexes

Four μ-2-chloroterephthalato binuclear iron(Ⅱ) complexes, namely [Fe2 (CTPHA) L4]-(ClO4)2, where L stands for 4,4'-dimethyl-2,2'-bipyridine (Me2-bpy); 2,9-dimethyl-l, 10-phenanthro-line (Me2-phen); 5-chloro-l, 10-phenanthroline (Cl-phen); 4, 7-diphenyl-l, 10-phenanthroline (Ph2-phen), respectively, and CTPHA represents 2-chlorolerephthalate dianion, have been synthesized and characterized. Based on the elemental analyses, molar conductance measurements and spectroscopic studies, extended CTPHA-bridged structures consisting of two iron(Ⅱ) ions, each in a distorted octahedral environment, are proposed for these complexes. [Fe2 CTPHA)-(Me2-bpy)4] (ClO2 (1) and [Fe2(CT-PHA)·(Me2-phen)4](ClO4)2 (2) complexes were characterized by variable temperature magnetic susceptibility (4-300 K) measurements and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, H = - 2JS1 · S2 , giving the exchange integrals J = - 1.28 cm-1 for 1 and J = - 1.85 cm-1 for 2. These r     

化合物[2,6-bis(benzo[1,2-d:4,5-d′]diimidazole-2′-yl)pyridine] 的合成、晶体结构和光物理性质

A new tridentate benzimidazole derivative, 2,6-bis (benzo[1,2-d:4,5-d′]diimidazole-2′-yl) -pyridine (Bzdiimpy),was prepared from o-phenylenediamine in five steps with improved methods according to the literature in good yield.The crystal structure was determined by X-ray diffraction analysis. It crystallized in monoclinic, space group P21/c,with a=1.1708(4) nm, b=2.4796(9) nm, c=1.215 9(4) nm,β=114.641(7)°, Z=1, R=0.035 0, wR2=0.0890. The bzdiimp molecule displayed an almost planar structure and formed a zig-zag chain through weak interactions between imidazole-N and [SnCl6]2--Cl. Its electronic absorption and emission spectra were measured and compared with the reported analogue 2,6-bis (benz[1,2-d:4,5-d′]imidazole-2′-yl)-pyridine (Bzp).     

Synthesis and characterization of platinum(II) and (IV) complexes containing hexamethyleneimine ligand: crystal structure of [PtII(hexamethyleneimine)2(cyclobutanedicarboxylato)]·H2O

A series of new platinum(II) and platinum(IV) complexes of the type [Pt^II(HMI)₂X] (where HMI=hexamethyleneimine, X=dichloro, sulfato, 1,1-cyclobutanedicarboxylato [CBDCA], oxalato, methylmalonato, or tatronato) and [Pt^IV(HMI)₂Y₂Cl₂] (where Y=hydroxo, acetato, or chloro) were synthesized and characterized by infrared (IR) spectroscopy, ¹³C and ¹⁹⁵Pt nuclear magnetic resonance (NMR) spectroscopy and elemental analysis. Among the complexes synthesized, [Pt^II(hexamethyleneimine)₂(1,1-cyclobutanedicarboxylato)]·H₂O was examined by single-crystal X-ray diffraction. The slightly distorted square planar coordination environment of the platinum metal includes the amino group of the hexamethyleneimine (HMI) molecule and the oxygen atoms of the carboxylato ligand. The cyclobutanedicarboxylic acid (CBDCA) molecule adopts six-member chelating rings with platinum. Hydrogen bonding plays an important part in holding the crystal lattice together.     

Synthesis of 3,3-bis(2-hydroxyethyl) and 3,3,3’-tris(2-hydroxyethyl) derivatives of 1,1’-[methylenebis(oxy)]bis(triaz-1-ene 2-oxides)

Synthetic procedures to access new potential NO donors that can generate NO in living systems, 3,3-bis(2-hydroxyethyl) and 3,3,3’-tris(2-hydroxyethyl) derivatives of 1,1’-[methylenebis(oxy)]bis(3,3-dialkyltriaz-1-ene 2-oxides), were elaborated. 3,3-Bis(2-acetoxyethyl)-1(chloromethoxy)triaz-1-ene 2-oxide reacts with 1-hydroxytriaz-1-ene 2-oxide sodium salts to give a series of alkylated 3,3-bis(2-acetoxyethyl) derivatives. Deacetylation of the latter produces 3-(2-hydroxyethyl)-11,11-dialkyl-6,8-dioxa-3,4,5,9,10,11-hexaazaundeca-4,9-dien-1-ol 4,10-dioxides and 11-alkyl-3-(2-hydroxyethyl)-6,8-dioxa-3,4,5,9,10,11-hexaazatrideca-4,9-diene-1,13-diol 4,10-dioxides.