Structure of bismuth(III) complexes with thiourea according to EXAFS spectroscopy Data

The EXAFS and XANES spectra of the solid complex Bi(tu)₆(ClO₄)₃ (1) (tu is thiourea) and the solutions 0.1 M Bi(ClO₄)₃ + 1.8 M tu + 1 M HClO₄ (2) and 0.05 M Bi(ClO₄)₃ + 1.5 M tu + 1 M HClO₄ (3) were recorded. For solid [Bi(tu)₆](ClO₄)₃, it was found that the first coordination shell of the Bi atom contains six sulfur atoms at distances of ～2.7–2.9 Å. It was assumed that binuclear bismuth complexes with Bi-S distances of ～2.8 and ～3.3 Å formed in Bi(ClO₄)₃ + (tu) + HClO₄ solutions.     

EXAFS investigation of nickel and cobalt precursors of homogeneous ziegler-type hydrogenation catalysts

A preliminary EXAFS study is reported of precursors of homogeneous hydrogenation catalysts obtained by addition of AlEt₃ to nickel or cobalt octoate solutions in benzene. For a given nickel octoate solution studied before reduction, monodentate coordination of the nickel cations to at least four carboxylic anions was established and accurate Ni...O₁, Ni...C₁ distances (i.e. 2.06±0.01 Å, 3.01±0.02 Å) were determined. The spectra of the reduced solutions are however clearly dominated by intense Ni^*...Ni or Co^*...Co signals at distances comparable to the relevant distances of the bulk metal, and thus suggest the presence of rather disordered, amorphous-like metal clusters. Strong evidence is also produced in favour of additional metal...carbon bonds which were often assumed to play an important role in the catalytic activity of these or related solutions.     

The molecular structure of tris-2,2,6,6-tetramethyl-heptane-3,5-dione indium: gas-phase electron diffraction and quantum chemical calculations

The molecular structure of tris-2,2,6,6-tetramethyl-heptane-3,5-dione indium, or In(thd)₃, has been determined by gas-phase electron diffraction monitored by mass spectrometry (GED/MS) and quantum chemical (DFT) calculations. Both the DFT calculations and the GED data collected at 387(8) K indicate that the molecules have D ₃ symmetry with a distorted anti-prismatic InO₆ coordination geometry. According to GED refinements, the twist angle θ, i.e. the angle of rotation of the upper and lower O₃ triangles in opposite directions relative to their positions in a regular prism is θ = ±24.9(1.2)° and the bond distances (r _h1) in the chelate ring are In–O = 2.127(4) Å, C–O = 1.268(3) Å and C–C = 1.411(3) Å, respectively. The DFT calculations yielded structure parameters in close agreement with those found experimentally.     

Synthesis and crystal structure of KBi(C6H4O7) · 3.5H2O

A novel compound, KBi(C₆H₄O₇) · 3.5H₂O (I), has been synthesized in the Bi(NO₃)₂-K₃(HCit) system (HCit^3? is an anion of citric acid C₆H₈O₇) at a component ratio (n) of 8 in a water-glycerol mixture, and its crystal structure has been determined. The crystals are unstable in air. The crystals are triclinic: a = 7.462 Å, b = 10.064 Å, c = 17.582 Å, α = 100.27°, β = 99.31°, γ = 105.48°, V = 1221.2 ų, Z = 2, space group $P\bar 1$ . In the structure of I, asymmetric binuclear fragments [Bi₂(Cit^4?)₂(H₂O)₂]^2? are linked through inversion centers into polymeric chain anions. Ions K⁺ and crystal water molecules are arranged in channels between the chains. The Bi(1)...Bi(2) distances in the binuclear fragment are 4.62 Å, and the Bi(1)...Bi(1) and Bi(2)...Bi(2) distances between bismuth atoms in the chain are 5.83 and 5.95 Å, respectively. The chains are linked through bridging oxygen atoms of the ligands Cit to form layers. In the centrosymmetric four-membered chelate ring Bi₂O₂ formed through Bi-O(Cit) bonds, the distances Bi(1)-Bi(1) are equal to 4.55 Å, and Bi(1)-O are 2.66 and 2.84 Å. The Bi-O bond lengths in I are in the range 2.12–3.16 Å. The Cit ligands act as hexadentate chelating/bridging ligands.     

Synthesis and Characterization of Three Homoleptic Bismuth Silanolates: [Bi(OSiR3)3] (R = Me,Et, iPr)

The bismuth tris(triorganosilanolates) [Bi(OSiR₃)₃] ( 1 , R = Me; 2 , R = Et; 3 , R = iPr) were prepared by reaction of R₃SiOH with [Bi(OtBu)₃]. Compound 1 crystallizes in the triclinic space group with Z = 2 and the lattice constants a = 10.323(1) Å, b = 13.805(1) Å, c = 21.096(1) Å and α = 91.871(4)°, β = 94.639(3)°, γ = 110.802(3)°. In the solid state compound 1 is a trimer as result of weak intermolecular bismuth‐oxygen interactions with Bi–O distances in the range 2.686(6)–3.227(3) Å. The coordination at the bismuth atoms Bi(1) and Bi(3) is best described as 3 + 2 coordination whereas Bi(2) shows a 3 + 3 coordination. The intramolecular Bi–O distances fall in the range 2.041(3)–2.119(3) Å. Compound 3 crystallizes in the orthorhombic space group Pbcm with Z = 4 and the lattice constants a = 7.201(1) Å, b = 23.367(5) Å and c = 20.893(1) Å, whereas the triethylsilyl‐derivative 2 is liquid. In contrast to [Bi(OSiMe₃)₃] ( 1 ) compound 3 is monomeric in the solid state, but shows similar intramolecular Bi–O distances in the range 1.998(2)–2.065(5) Å. The bismuth silanolates are highly soluble in common organic solvents and strongly moisture sensitive. Compound 1 shows the lowest thermal stability.     

Structure of Methanol Solvated Iodozinc(II) Complexes in Solution

The structures of the solvated zinc ion and the solvated zinc–iodide complexes in methanol solution have been determined by EXAFS. The zinc ion is six-coordinated in an octahedral fashion with a mean Zn–O bond distance of 2.071(4) Å. According to the stability constants of the zinc–iodide system in methanol solution the first complex, ZnI⁺, is suppressed, which may indicate that a coordination change takes place at this step. On the other hand, the second complex, ZnI₂, predominates at excess of iodide. The methanol solvated ZnI₂ complex has a tetrahedral structure with mean Zn–I and Zn–O bond distances of 2.55(1) and 1.99(1) Å, respectively. The mean Zn–I bond distance in a solution containing a maximal content of ZnI⁺, ca. 12%, strongly indicates that the first complex also has a tetrahedral structure.     

Structure of Aqueous Gallium(III) Bromide Solutions Over a Temperature Range 80–333 K by Raman Spectroscopy, X-ray Absorption Fine Structure, and X-ray Diffraction

The structure and complex formation of concentrated aqueous gallium(III) bromide (GaBr₃) solutions have been investigated over a temperature range 80–333 K by Raman spectroscopy, X-ray absorption fine structure (XAFS), and X-ray diffraction. The Raman spectra obtained at various [Br^?]/[Ga³⁺] molar ratios and temperatures have shown that complex formation between Ga³⁺ and Br^? occurs as a predominant species, with [GaBr₄]^? at [Ga³⁺] as high as 1～2 M (M = mol?dm ^?3) and [Br^?]/[Ga³⁺] ratios > ～2, and that cooling of the solutions favors the formation of the aqua Ga³⁺. The intermediate species were not seen in the Raman spectra. The XAFS data have revealed that the aqua complex has a sixfold coordination as [Ga(H₂O)₆]³⁺ with a Ga³⁺–H₂O distance of (1.96 ± 0.02) Å, whereas the [GaBr₄]^? complex has a Ga³⁺–Br^? distance of (2.33± 0.02) Å, and that vitrification of the aqueous GaBr₃ solution at liquid nitrogen temperature shifts the equilibrium toward the aqua complex. The X-ray diffraction data at different subzero temperatures have shown a tendency of decreasing Ga³⁺–Br^? and increasing Ga³⁺–H₂O interactions with lowering temperature, confirming the preference of aqua Ga³⁺ in the supercooled liquid state as well as in the glassy state. The Ga³⁺–H₂O distance of ～1.8 Å for the tetrahedral coordination was found in a 2.01 M gallium(III) bromide solution with a [Br^?]/[Ga³⁺] ratio of 3.7 and gradually increased to a value of 1.92 Å for octahedral geometry with decreasing temperature, suggesting that equilibrium shifts from [GaBr₄]^? to [Ga(H₂O)₆]³⁺ through intermediate species, [GaBr _n ]^(3?n)+ (n = 2 and 3). The Ga³⁺–Br^? and Br^?–Br^? distances within [GaBr₄]^? with an almost tetrahedral symmetry are (2.35± 0.02) and (3.82± 0.03) Å, respectively. The Ga³⁺ has the second hydration shell at (4.03± 0.03) Å and the hydration of Br^? is characterized with a Br^?–H₂O distance of (3.35± 0.02) Å at all temperatures investigated.     

Bis(triphenylphosphin)iminium-bis(methoxo)phthalocyaninato(2–)ferrat(III) – Synthese und Kristallstruktur

Bis(triphenylphosphine)iminium Bis(methoxo)phthalocyaninato(2–)ferrate(III) – Synthesis and Crystal Structure Chlorophthalocyaninato(2–)ferrate(III) reacts with bis(triphenylphosphine)iminium hydroxide in methanol/acetone solution to yield blue crystals of bis(triphenylphosphine)iminium bis(methoxo)phthalocyaninato(2–)ferrate(III). The complex salt crystallizes as an acetone/methanol solvate (^bPNP)[Fe(OCH₃)₂pc^2–] · (CH₃)₂CO · 1.5 CH₃OH in the triclinic space group P 1 (no. 2) with the cell parameters a = 13.160(5) Å, b = 15.480(5) Å, c = 17.140(5) Å, α = 97.54(5)°, β = 91.79(5)°, γ = 95.44(5)°. The Fe atom is located in the centre of the pc^2– ligand coordinating four isoindole N atoms (N_iso) of the pc^2– ligand and two O atoms of the methoxo ligands in a mutual trans arrangement. The average Fe–O and Fe–N_iso distances are 1.887 and 1.943 Å, respectively. The cation adopts the bent conformation (< P–N–P = 140.4(2)°) with P–N distances of 1.579(3) and 1.575(3) Å.     

EXAFS and DFT studies of microscopic structure with different density upon Zn(II) adsorption on anatase TiO2

Microscopic structures of Zn(II) adsorbed on anatase TiO₂ surface with different densities were studied using extended X-ray absorption fine structure (EXAFS) spectroscopy and density functional theory (DFT) calculation. Quantitative analysis of the EXAFS spectra showed that microscopic structures of Zn(II) were fourfold coordinated complexes, and different microscopic structures were present of the solid surface. Three modes of corner–corner/sharing-corner/sharing-edge adsorptions on anatase (101) face cluster were calculated by the DFT method. The results from DFT method were consistent with the EXAFS fittings. The optimized Zn–O average distance of the Zn–O tetrahedron was determined as about 2.00 Å. The Zn–Ti distance was 3.69 Å for the corner–corner adsorption, 3.35 Å for the sharing-corner adsorption, and 3.02 Å for the sharing-edge adsorption. According to the adsorption energies calculated by the DFT method, the microscopic structure of corner–corner adsorption was less stable than those of the other adsorption modes. With the increasing adsorption density, the corner–corner adsorption mode would be enhanced more intensively than the other adsorption modes.     

Characterization and thermal analysis of thiourea and bismuth trichloride complex

A complex of thiourea and bismuth trichloride has been synthesized. Its composition is Bi₃Cl₉[SC(NH₂)₂]₇. Crystallographic data are a = 7.141(2) Å, b = 8.820(3) Å, c = 16.365(5) Å, α = 99.389(4)°, β = 95.422(4)°, γ = 106.177(4)°, triclinic system. There are the mononuclear anion [BiCl₅SC(NH₂)₂]^2? and the dinuclear cation {Bi₂Cl₄[SC(NH₂)₂]₆}²⁺ with the Bi–Cl–Bi bridge bonds in the complex. The electric conductance of the absolute methanol solution contained the complex indicates that the complex is an ionic compound. Raman spectra indicate that the bismuth ion is coordinated by the sulfur atoms of the thiourea. The thermal analysis verifies the structure of complex. The TG–MASS curves show the structure rearrangement in the complex at about 118 °C. The DSC curves and calculation means that the structure rearrangement is irreversible.     

Bismuth triple-decker phthalocyanine: synthesis and structure

Triclinic crystals of bismuth(III) triple-decker phthalocyanine, Bi₂Pc₃, Pc=C₃₂H₁₆N₈²⁻, were grown directly by the reaction of Bi₂Se₃ with 1,2-dicyanobenzene at 220°C. The Bi₂Pc₃ molecule is centrosymmetric with the bismuth atoms located closer to the peripheral phthalocyaninato(2−) rings than to the central ring. Each bismuth(III) ion is connected by four N-isoindole atoms to the peripheral and by four N-isoindole to the central Pc ring with average distances of 2.333 and 2.747 Å, respectively. This indicates a stronger connection of Bi(III) to the peripheral saucer-shaped macrocyclic rings than to the central rings. The neighbouring phthalocyaninato(2−) moieties in the Bi₂Pc₃ molecule are separated by a distance of 3.101(5) Å. The central Pc ring is rotated by 36.4° with respect to the peripheral ones. Differences in Bi–N bond lengths are a result of interaction of the bismuth ion with peripheral and central rings as well as the repulsion forces between two bismuth ions in the same Bi₂Pc₃ molecule, which are separated by a distance of 3.839(2) Å. The crystal packing is characterized by a distance of 3.56 Å between Pc rings of neighbouring Bi₂Pc₃ molecules.     

Tetranuclear manganese (III) salicylaldoxime ensemble

Crystal structure of {[Mn(salicylaldoximeH)(salicylaldoxime)]₄} · 3CHCl₃ 1 formed by the interaction of MnCl₂ · 4H₂O and salicylaldoxime in a 1:1 ratio is described. The compound crystallizes in the orthorhombic space group Pbca (No 61) with the lattice parameters; a = 27.769 (3), b = 22.672 (2), c = 21.650 (2) Å, V = 13630 (2) Å³, Z = 8, R ₁ = 0.0776, wR ₂ = 0.2356, S = 1.164. The cluster with four Mn (III) centers formed by four terminal and four bridging salicylaldoxime ligands results in a central rotating wheel-like core with the Mn–Mn separation varying from 3.531 to 3.576 Å and with the diagonal distances being 4.156–4.165 Å. Four intramolecular H-bonds between a terminal oxime (NOH) group and the adjacent phenolate oxygen atom of another ligand stabilize the structure of the cluster. Spectral, magnetic, and cyclic voltammetry studies corroborate a stable Mn (III) tetramer.     

Tri-<Emphasis Type="Italic">p</Emphasis>-Tolylbismuth Diperchlorate and μ-Oxo-bis[(perchlorato)tri-<Emphasis Type="Italic">p</Emphasis>-tolylbismuth]: Synthesis and Structure

Tri-p-tolylbismuth perchlorate (1) and μ-oxo-bis[(perchlorato)tri-p-tolylbismuth] (2) have been synthesized by the reaction between tri-p-tolylbismuth dibromide and silver perchlorate and its hydrate. The complexes have been studied by chemical analysis, IR spectroscopy, and X-ray diffraction. Complex 1 is triclinic, space group Pī, Z = 4, a =10.7271(9) Å, b = 13.5585(11) Å, c = 18.1592(13) Å, α = 110.867(3)°, β = 94.944(3)°, γ = 96.888(3)°, V = 2426.3(3) Å3, ρ_calcd = 1.865 g/cm3; complex 2 crystallizes in trigonal symmetry, space group R\(\bar 3\), a = 13.1157(2) Å, c = 22.1959(2) Å, γ = 120°, V = 3306.64(8) ų, ρ_calcd = 1.777 g/cm³. The bismuth atoms in the molecular structure of complex 1 have a distorted trigonal bipyramidal coordination to the apically arranged oxygen atoms of perchlorate ions (Bi–C, 2.180(5)–2.201(5) Å; Bi–O, 2.324(4)–2.355(4) Å; OBiO axial angles, 170.1(1)°, 174.5(1)°). The structure of complex 2 contains binuclear [p-Tol₃Bi(ClO₄)]₂O molecules (Bi–O, 2.371(15), 1.9107(7) Å; OBiO axial angle, 180.0°).     

The <Emphasis Type="Italic">r</Emphasis><Subscript>0</Subscript> structural parameters of equatorial and axial chlorocyclobutane,conformational stability from temperature dependent infrared spectra of xenon solutions,and vibrational assignments

Variable temperature (?55 to ?100 °C) studies of the infrared spectra (4,000–400 cm^?1) of chlorocyclobutane, c-C₄H₇Cl, dissolved in liquid xenon have been carried out. The infrared spectrum (4,000–100 cm^–1) of the gas has also been recorded. For this puckered ring molecule the enthalpy difference between the more stable equatorial conformer and the axial form, has been determined to be 361 ± 17 cm^?1 (4.32 ± 0.20 kJ/mol). This stability order is consistent with that predicted by ab initio calculations but the ?H is much lower than the average energy value of 646 ± 73 cm^?1 obtained from the MP2 ab initio calculations or 611 ± 28 cm^?1 from the B3LYP density functional theory calculations. The percentage of the axial conformer present at ambient temperature is estimated to be 15 ± 1%. By utilizing previously reported microwave rotational constants for both conformers combined with ab initio MP2(full)/6–311+G(d,p) predicted structural values, adjusted r ₀ parameters have been obtained. The determined heavy atom structural parameters for the equatorial conformer are: the distances C–Cl = 1.783(5), C₁–C₄ = 1.539(3), C₄–C₆ = 1.558(3) Å, and angles ∠C₆C₄C₁ = 86.9(5), ∠C₄C₁C₅ = 89.7(5)°, and for the axial conformer are: the distances C–Cl = 1.803(5), C₁–C₄ = 1.547(3), C₄–C₆ = 1.557(3) Å, and angles ∠C₆C₄C₁ = 86.3(5), ∠C₄C₁C₅ = 88.9(5) and the puckering angles for the equatorial and axial conformers are 30.7(5)° and 22.3(5)°, respectively. The conformational stabilities, harmonic force fields, infrared intensities, Raman activities, depolarization ratios and vibrational frequencies have been obtained for both conformers from MP2(full)/6-31G(d) ab initio calculations and compared to experimental values where available. The results are discussed and compared to the corresponding properties of some similar molecules.     

Crystal structure of hexakis-(<Emphasis Type="Italic">N</Emphasis>-methylthiourea) bismuth(III) triperchlorate

A bismuth(III) complex of N-methylthiourea (Mtu, C₂H₆N₂S) [Bi(C₂H₆N₂S)₆](ClO₄)₃ has been synthesized, and its crystal structure has been determined. The structure is built of octahedral Bi(Mtu) ₆ ³⁺ cations and ClO ₄ ^? anions. Sulfur atoms are coordinated to bismuth(III) (at axis 2) at octahedron vertices (Bi-S, 2.7670(8), 2.8142(8), and 2.8315(8) Å); angles SBiS vary from 82.26(3)° to 96.13(2)°. The presence of amino groups and oxygen atoms in the structure results in the emergence of numerous hydrogen bonds (HBs). All H atoms of amino groups are involved in HBs; one of them is bound to the sulfur atom. One of the oxygen atoms of ClO ₄ ^? anions does not participate in HBs.     

New cyclen derivative ligand for thorium(IV) separation by solvent extraction

A new N-containing ligand, 1,4,7,10-tetra-(4-nitrobenzyl)-1,4,7,10-tetraazacyclo-dodecane (L), was synthesized, and its structure was determined by ¹H NMR, high resolution mass spectrometry and X-ray diffraction. L crystallized in the monoclinic system (P2₁/n space group; a = 7.7895(2) Å, b = 22.9592(5) Å, c = 9.9204(2) Å; α = 90.00°, β = 105.481(3)°, γ = 90.00°; Z = 2). Slope analysis and the continuous variation method demonstrated that 1:2 complexes between Th(IV) and L are formed; furthermore, the XPS analysis suggested that two oxygen atoms might be provided by two water molecules and that eight nitrogen atoms might be provided by two L molecules to form a ten-coordinate compound with Th(IV). The extraction equilibrium constant for the complex formation between Th(IV) and L was logK _ex = 6.95 ± 0.15 (25 °C), and the Gibbs free energy, ΔG ^o (25 °C), of the 1:2 Th–L complex in dichloromethane was ?39.56 kJ/mol. The L ligand in dichloromethane only slightly extracted Th(IV) from HNO₃ solution at pH = 1–3; however, an extraction efficiency of E = 94.9 ± 0.3 % was observed at pH = 4.63. The selectivity of L for the Th(IV) cation over other cations (i.e., Cs(I), Sr(II), Y(III), La(III), Sm(III), Eu(III), U(VI), and ²⁴¹Am(III)) was evaluated. Furthermore, the stripping experiments showed that the stripping agent (0.5 mol/L Na₂CO₃ + 0.1 mol/L EDTA) could provide an optimal condition for stripping thorium, and thorium recovery was up to 91.6 ± 0.1 %.     

An electron-diffraction study of the molecular structure of gaseous perbromyl fluoride and calculation of its force field and vibrational amplitudes

The molecular structure of FBrO₃ has been studied by gas-phase electron diffraction. Least-squares refinements of the molecular geometry using fixed spectroscopic amplitudes revealed two geometrical minima. Initially, the amplitudes employed were derived from diagonal force fields obtained by spectroscopic least-squares refinements to fit observed and calculated wave numbers; for each geometry there are two spectroscopic minima. In the lowest geometrical minimum the wave number agreement is poor, however, the introduction of the ∠OBrO/∠FBrO interaction force constant removed the discrepancies; the resulting force field is F(Br-O) = 6.92 ± 0.02 mdyn Å^?1F(Br-F) = 3.22 ± 0.03 mdyn Å^?1, F(∠OBrO) = 1.06 ± 0.02 mdyn Å, F(∠FBrO) = 0.81 ± 0.03 mdyn Å, F(∠OBrO/∠FBrO) = ?0.19 ± 0.02 mdyn Å. In the corresponding geometrical minimum r_g(Br-O) = 1.582 ± 0.001 Å, r_g(Br-F) = 1.708 ± 0.003 Å, r_α(∠OBrO) = 114.9 ± 0.3°, r_α(∠FBrO) = 103.3 ± 0.3°. Perpendicular amplitude correction coefficients, calculated for each force field employed, were used throughout to relate the interatomic distances through the r_α-structure. The geometries of the r_α^o- and r_e-structures are estimated.     

SYNTHESIS AND CHARACTERIZATION OF MANGANESE(III) HYDROXYL-CONTAINING SCHIFF-BASE COMPLEXES: [Mn(III)(Hvanpa)2(NCS)] AND [Mn(III)(Hvanpa)2]Cl · H2O (H2vanpa ˭ 1-(3-METHOXYSALICYLALDENEAMINO)-3-HYDROXYPROPANE)

Abstract

The manganese complexes, [Mn(III)(Hvanpa)₂(NCS)] (1) and [Mn(III)(Hvanpa)₂]Cl · H₂O (2), have been prepared and the crystal structure of complex 2 determined using X-ray crystallography. The monomeric complex has a six-coordinate octahedral geometry. The complex crystallizes in the triclinic space group P-1 with a = 11.446(5) Å, b = 12.782(6) Å, c = 9.023(3) Å, α = 93.92(3)°, β = 97.05(3)°, γ = 65.42(2)°, V = 1169.0(9) ų and Z = 2. The Mn-O and Mn-N distances in the equatorial plane are in agreement with those found for other manganese (III) Schiff-base complexes. In the axial direction, the Mn-O distances of 2.256(3) and 2.236(3) Å, respectively, are about 0.4 Å longer than those in the equatorial plane due to Jahn-Teller distortion at the d ⁴ manganese(III) center. In the crystal, each chloride ion is linked through hydrogen bonding with two hydrogen atoms from the coordinated hydroxyl groups at the apical site. The lattice water molecules also interact with the phenolic oxygen atoms through hydrogen bonding.     

XAFS spectroscopic study of Tc2(O2CCH3)4X2 (X = Cl,Br)

Technetium dimers Tc₂(O₂CCH₃)₄X₂ (X =?Cl, Br) were synthesized and studied by X-ray Absorption Fine Structure spectroscopy (XAFS). EXAFS analysis gave for Tc₂(O₂CCH₃)₄Cl₂: d Tc-Tc =?2.18(1) Å, d Tc–Cl =?2.43(1) Å and for Tc₂(O₂CCH₃)₄Br₂: d Tc–Tc =?2.19(1) Å, d Tc-Br =?2.63(1) Å. The Tc Tc separations are in agreement with Raman studies while the Tc–X distances are somewhat larger. Comparison with other Tc(III) quadruply bonded dimers indicates that the carboxylate compounds exhibit larger Tc–Tc separations. The effect of the terminal ligand (nature and position) on the Tc–Tc separation is discussed.     

A Novel Dinuclear Nickel(II) Complex with Three Bridges of Cl–, OAc– and (‐OCH2CH2O‐) Group of N,N, N′, N′‐Tetrakis(2‐benzimidazolyl methyl‐1, 4‐di‐ethylene amino) Glycol Ether

The novel dinuclear Ni²⁺ complex [Ni₂(μ‐Cl)(μ‐OAc) (EGTB)]·Cl·ClO₄·2CH₃OH, where EGTB is N, N, N′, N′‐tetrakis (2‐benzimidazolyl methyl‐1, 4‐di‐ethylene amino)glycol ether, crystallizes in the orthorhombic space group Pnma with a = 15.272(2), b = 14.768(2), c = 22.486(3) Å, V = 5071.4(12) ų, Z = 4, D_calc = 1.414 g cm^?3, and is bridged by triply bridging agents of a chloride ion, an acetate and an intra‐ligand (‐OCH₂CH₂O‐) group. The nickel coordination geometry is that of a slightly distorted octahedron with a NiN₃O₂Cl arrangement of the ligand donor atoms. The Ni–Cl distance is 2.361(2) Å, and two Ni–O distances are 1.996(5) and 2.279(6) Å. The three Ni–N distances are 2.033(7), 2.060(6), and 2.166(6) Å with the Ni–N bond trans to an ether oxygen the shortest, the Ni–N bond trans to an acetate oxygen the middle and the Ni–N bond trans to Cl the longest.