Anionic charge effects on the crystal structures of Re6 octahedral cluster based compounds: The structure of the cubic bromide K2Re6S6Br8

The title compound synthesized by solid state reaction crystallizes in the cubic system (Pn-3) witha=13.433 Å. The structure has been determined by singlecrystal X-ray diffraction and shows that the compound is based on isolated |(Re₆S ₆ ⁱ Br ₂ ⁱ )Br ₆ ^a |^2? units. The K⁺ cations occupy two different sites. Steric effects lead to the switching from the cubic symmetry present in KRe₆Se₅Cl₉ to the monoclinic one in the case of KRe₆S₅Br₉ and again the former cubic symmetry in the new compound K₂Re₆S₆Br₈.     

Single-crystal structure of Cs2Re6S6Br8 rhenium thiobromide with acentric Re6 octahedral cluster units

Cs₂Re₆S₆Br₈ (trigonal, a = 10.001(5) Å, c = 14.676(5) Å) exhibits the same structure as Cs₂Mo₆Cl₈Br₆ and Cs₂Mo₆Br₁₄ that were described in a noncentro-and centrosymmetric space groups, respectively. The structure has been refined in P31c space group from a single crystal of actual composition Cs_1.95(1)Re₆S_5.82(3)Br_8.19(3) close to the cesium-rich end of the solid solution Cs₂Re₆S₆Br₈ — CsRe₆S₅Br₉. The centrosymmetry is respected by almost all the atoms of the asymmetric unit, but it is clearly broken by significant differences in the S/Br statistical distribution of the disordered “inner” ligands around the Re₆ cluster. Structural refinements from data collected at 100 K revealed that the Cs cation disorder is static. From the structure refinements, the stable isomers of the [Re₆S₆Br₂] and [Re₆S₅Br₃] cluster cores have been unambiguously determined.     

A morphotropic series of the cluster complexes [Ln(DMF)8][Re6Q7Br7] (Q = S, Se): Synthesis, structure, and thermal transformations

The reactions of the octahedral anionic complexes [Re₆Q₇Br₇]^3? (Q = S, Se) with lanthanide bromides in DMF were studied. The reactions gave a series of compounds [Ln(DMF)₈][Re₆Q₇Br₇] (Q = S, Se) containing [Ln(DMF)₈]³⁺ complex cations. The compounds were studied by single-crystal and powder X-ray diffraction and thermal analyses. The crystal structures of [Ln(DMF)₈][Re₆S₇Br₇] with Ln = La (I), Ce (II), Nd (III), Eu (IV), and Lu (V) and [Ln(DMF)₈][Re₆Se₇Br₇] with Ln = La (VI), Ce (VII), Pr (VIII), and Lu (IX) were determined. It was found that [Ln(DMF)₈][Re₆Q₇Br₇] (Q = S, Se) can be divided into three structural groups: I, II, and VI (type A), VII (type B), and III–V, VIII, IX (type C). The complex [Pr(DMF)₈][Re₆Se₇Br₇] was found to crystallize in two polymorphous modifications with type B and C structures. Presumably, the morphotropic transitions in the [Ln(DMF)₈][Re₆Q₇Br₇] series (Q = S, Se) are mainly related to the change in the configuration of the [Ln(DMF)₈]³⁺ cations, resulting in a change in the packing motif of large complex ions in the crystals. The compounds [Ln(DMF)₈][Re₆Se₇Br₇] decompose according to a stepwise pattern, which suggests an intermediate formation of the complexes [Ln(DMF)₆][Re₆Se₇Br₇] (this was proved for Ln = Yb, Lu) with subsequent more extensive transformations, which affect also the cluster anion.     

New compounds in the cesium sulfobromide rhenium octahedral cluster chemistry: syntheses and crystal structures of Cs4Re6S8Br6 and Cs2Re6S8Br4

The exploration of the CsReSBr system, in order to identify new phases based on octahedral cluster anions, has produced single crystals of Cs₄Re₆S₈Br₆ (1) (trigonal, space group P-6c2, a=9.7825 (3) Å, c=18.7843 (5) Å, V=1556.77 (1) ų, Z=2, density=5.09 g cm⁻³, μ=36.07 mm⁻¹) and Cs₂Re₆S₈Br₄ (2) (monoclinic, space group P2₁/n, a=6.3664 (1) Å, b=18.4483 (4) Å, c=9.3094 (2) Å, β=104.2618 (8)°, V=1059.69 (4) ų, Z=2, density=6.14 g cm⁻³, μ=45.83 mm⁻¹). These two compounds have been obtained by high-temperature solid state route. Their structures have been solved and refined from single crystal X-ray diffraction data. The structure of Cs₄Re₆S₈Br₆ presents isolated anionic cluster units inscribed in a (Cs⁺)₁₂ cuboctahedron and the one of Cs₂Re₆S₈Br₄ exhibits ReS^i-a,a-iRe inter-unit bridges. The framework of the latter presents then a strongly 1-D character.     

New synthetic routes for the preparation of the triangular trinuclear clusters of tungsten-containing bromine atoms as terminal ligands: Structural characterization of [W3S4Br3(depe)3]PF6·0.5C7 H8 and [W3S4Br3(depe)3]Br·2CH3OH

Synthetic methods are reported for the preparation of compounds containing the trinuclear triangular cluster [W₃S₄Br₃(depe)₃[⁺. These involve reactions between WBr₅ and NaB(C₂ H₅)₃H or NaBH₄ as reducing agent in THF, and subsequent addition of methanolic solutions of NaHS and depe ligand. Both compounds, [W₃S₃Br₃(depe)₃]PF₆·0.5C₇H₈,1, and [W₃S₄Br₃(depe)₃]Br·2CH₃OH,2, are characterized by x-ray single crystal studies. Compounds1 and2 crystallize in space group \(P\bar 1\) . For1,a=10.427 (3) Å,b=15.415(4) Å,c=18.140(5) Å, α=79.36(2)°, β=73.59(2)°, γ=81.54(2)°, andV=2734.8(2) ų;R=0.050 and for 2a=10.491(3) Å,b=15.074(3) Å,c=18.246 Å, α=95.76(2)°, β=105.82(2)°, γ=98.18(2)°, andV=2718.4(3) ų;R=0.081. The two cations in1 and2 possess C₃ symmetry. The W-W distances are in the range 2.783?2.891 Å (for1) and 2.778?2.785 Å (for2) and the average W-Br distances in1 and2 are 2.616[2] Å and 2.594[4] Å, respectively. Each metal atom in the [W₃S₄Br₃(depe)₃]⁺ ions is attached to one capping sulfur atom, two bridging sulfur atoms, one bromine atom, and one chelating depe ligand. One P atom in depe ligand istrans to μ₃-S and the otherP atom istrans to a μ₂-S atom. UV-Vis and NMR spectra for these compounds are also reported.     

Cs4Re6S13 und Cs4Re6S13,5 – zwei Verbindungen mit [Re6S8]-Baueinheiten in geringfügig variierten Gerüststrukturen

Cs₄Re₆S₁₃ and Cs₄Re₆S_13.5 — Two Compounds with [Re₆S₈] Clusters Slightly Differing as to their Framework Structures Cs₄Re₆S₁₃ was synthesized by the reaction of cesium carbonate with rhenium at 800°C in an argon atmosphere charged with sulphur. The preparation of Cs₄Re₆S_13.5 succeeded by an analogous procedure using a stream of H₂S. Structural investigations on single crystals revealed atomic arrangements in which [Re₆S₈] clusters are linked threedimensionally by S_n^2? bridges. In the compound Cs₄Re₆S₁₃ $\buildrel \wedge \over =$ Cs₄[Re₆S₈]S_2/2(S₂)_4/2 the rhenium atoms of adjacent Re₆-octahedra are connected by sulphide and disulphide bridges in a ratio of 1:2. In the compound Cs₄Re₆S_13.5 $\buildrel \wedge \over =$ Cs₄[Re₆S₈]S_2/2(S₂)_3/2(S₃)_1/2 one disulphide bridge is replaced by one trisulphide bridge. The nearly regular Re₆-octahedra correspond with a diamagnetic 24-electron configuration.     

Cl i /Br-Substitution in der Wolframchlorosäure (H3O)2[W6Cl 8 i ]Cl 6 a ·6H2O

A method for preparing chlorotungstic acid $$(H_3 O)_2 [W_6 Cl_8 i]Cl_6 a \cdot 6H_2 O$$ in good yield is given. On thermal degradation of the acid, the stages $$(H_2 O)_2 [W_6 Cl_8 ]Cl_6 ,[W_6 Cl_8 ]Cl_4 \cdot 2H_2 O and [W_6 Cl_8 ]Cl_4 $$ are isolable. Chlorotungstic acid and its partial Br ⁱ -substitution products can be precipitated almost quantitatively as $$(Oxin \cdot H)_2 [W_6 X_8 ]X_6 $$ When boiled with strong aqueous or aqueous-ethanolic HBr the substitution of Cl ^a and also partial Cl ⁱ /Br substitution occurs. In the same way I ⁱ can be introduced. The inverse reaction (substitution of Br ⁱ by Cl) is not possible. In ethanolic HB in the case of Cl ⁱ /Br substitution an induction period is observed.     

Calix[4]arene-bis(t-octylbenzo-18-crown-6) as an extraordinarily effective macrocyclic receptor for the univalent thallium cation

From extraction experiments and $ \gamma $ -activity measurements, the exchange extraction constant corresponding to the equilibrium Tl⁺ (aq) + 1·Cs⁺ (org) ? 1·Tl⁺ (org) + Cs⁺ (aq) taking place in the two-phase water–phenyltrifluoromethyl sulfone (abbrev. FS 13) system (1 = calix[4]arene-bis(t-octylbenzo-18-crown-6); aq = aqueous phase, org = FS 13 phase) was evaluated as log K _ex (Tl⁺, 1·Cs⁺) = 1.7 ± 0.1. Further, the extraordinarily high stability constant of the 1·Tl⁺ complex in FS 13 saturated with water was calculated for a temperature of 25 °C: log β _org(1·Tl⁺) = 13.1 ± 0.2. Finally, by using quantum mechanical DFT calculations, the most probable structure of the cationic complex species 1·Tl⁺ was derived. In the resulting 1·Tl⁺ complex, the “central” cation Tl⁺ is bound by eight bond interactions to six oxygen atoms from the respective 18-crown-6 moiety and to two carbons of the corresponding two benzene rings of the parent receptor 1 via cation–π interaction.     

Niobium-chloride octahedral clusters as building units for larger frameworks

A systematic theoretic study on clusters containing edge-bridged octahedral metal units [Nb₆Cl₁₂] ⁿ (n?=?2, 3, or 4) and a large variety of ligands has been performed. The benchmark results on the [Nb₆Cl ₁₂ ⁱ ] ⁿ⁺ and [Nb₆Cl ₁₂ ⁱ Cl ₆ ^a ] ⁿ (n?=?2, 3 or 4) cluster units demonstrated the reliability of GGA PBE functional in combination with ZORA TZP basis set for the Nb-containing coordination compounds. The geometrical, electronic, and vibrational properties of large variety of substituted Nb₆Cl ₁₂ ⁱ Y ₆ ^a clusters have been provided. One- and two-dimensional structures with a [Nb₆Cl ₁₂ ⁱ (Bipyr) _x Cl _6?x ^a ] (x?=?2 and 4) building blocks have been proposed as good and stable candidates for new coordination polydimensional materials.     

The lifetime of the (μHe) 2S + metastable state in helium gas

The ion-clustering mechanism of the quenching of the metastable 2S-state of the muonic helium ion (μHe) _2S ⁺ in gaseous helium is studied on the basis of quantum-chemical calculations of clusters He _n (μHe)⁺. It is shown that the quenching rates do not depend on the cluster ordern atn ≥ 2. In the helium gas at the pressure 0.1 ?p(atm) ? 10 the quenching of (μHe) _2S ⁺ proceeds, mainly, at the vibrationally excited levels of He(μHe) _2S ⁺ cluster, while atp ? 10 atm, at the ground vibrational state of the cluster He₂(μHe) _2S ⁺ . Atp ≥0.1 atm the calculated quenching rates agree with the recent experimental data.     

Thermal analysis, phase transitions and molecular reorientations in [Sr(OS(CH3)2)6](ClO4)2

Thermal analysis (TG/DTG/QMS), performed for [Sr(OS(CH₃)₂)₆](ClO₄)₂ in a flow of argon and in temperature range of 295–585 K, indicated that the compound is completely stable up to ca. 363 K, and next starts to decompose slowly, and in the temperature at ca. 492 K looses four (CH₃)₂SO molecules per one formula unit. During further heating [Sr(DMSO)₂](ClO₄)₂ melts and simultaneously decomposes with explosion. Differential scanning calorimetry (DSC) measurements performed in the temperature range of 93–370 K for [Sr(DMSO)₆](ClO₄)₂ revealed existence of the following phase transitions: glass ? crystal phase Cr5 at T _g  ≈ 164 K (235 K), phase Cr5 → phase Cr4 at $ T_{\text{c6}}^{\text{h}} $  ≈ 241 K, phase Cr4 → phase Cr3 at $ T_{\text{c5}}^{\text{h}} $  ≈ 255 K, phase Cr3 → phase Cr2 at $ T_{\text{c4}}^{\text{h}} $  ≈ 277 K, phase Cr2 ? phase Cr1 at $ T_{\text{c3}}^{\text{h}} $  ≈ 322 K and $ T_{\text{c3}}^{\text{c}} $  ≈ 314 K, phase Cr1 ? phase Rot2 at $ T_{\text{c2}}^{\text{h}} $  ≈ 327 K and $ T_{\text{c2}}^{\text{c}} $  ≈ 321 K and phase Rot2 ? phase Rot1 at $ T_{\text{c1}}^{\text{h}} $  ≈ 358 K and $ T_{\text{c1}}^{\text{c}} $  ≈ 347 K. Entropy changes values of the phase transitions at $ T_{\text{c1}}^{\text{h}} $ and $ T_{\text{c2}}^{\text{h}} $ (?S ≈ 79 and 24 J mol^?1 K^?1, respectively) indicated that phases Rot1 and Rot2 are substantially orientationally disordered. The solid phases (Cr1–Cr5) are more or less ordered phases (?S ≈ 7, 10, 4 and 3 J mol^?1 K^?1, respectively). Phase transitions in [Sr(DMSO)₆](ClO₄)₂ were also examined by Fourier transform middle infrared spectroscopy (FT-MIR). The characteristic changes in the FT-MIR absorption spectra of the low- and high-temperature phases observed at the phase transition temperatures discovered by DSC allowed us to relate these phase transitions to the changes of the reorientational motions of DMSO ligands and/or to the crystal structure changes.     

Oxidation and reductive bromination of Bis(4-tert-butylphenyl)aminoxyl

One-electron oxidation of bis(4-tert-butylphenyl)aminoxyl with antimony pentachloride and bromine leads to the formation of oxoammonium salts with anions SbCl ₆ ^? and Br ₃ ^? respectively. The salt with the Br ₃ ^? anion converted at heating into a mixture of bromodiphenylamines which formed also from the aminoxyl as a result of previously unknown reaction of three-electron reductive bromination. The mechanisms of these reactions were assumed.     

Electrochemical control of association and deposition of tetraviologen calix[4]resorcin

The association and deposition of tetraviologen calix[4]resorcin MVCA-C ₅ ⁸⁺ can be controlled using the electrochemical reduction-reoxidation cycle of viologen units. The monomeric MVCA-C ₅ ⁸⁺ was converted into the highly molecular (MVCA-C ₅ ^4+· ) _n associate (π-polymer) by reducing it to the MVCA-C ₅ ^4+· tetra(radical cation) and completely returns to the starting monomeric state by reverse oxidation. The reduction to the neutral state MVCA-C ₅ ⁰ allowed calixresorcin to pass from solution to precipitate and the reverse oxidation led to its returning in solution.     

Crystal structure of the octahedral cluster complex trans-[{Re6S8}(pyz)4I2]·2pyz

The cluster complex of the composition trans-[{Re₆S₈}(pyz)₄I₂]· 2pyz (pyz is pyrazine) is obtained by the reaction of Cs₄[{Re₆S₈}I₆] with molten pyrazine. The compound crystallizes in the triclinic space group $P\bar 1$ with the following unit cell parameters: a = 9.0562(7) Å, b = 10.2502(7) Å, c = 12.6783(9) Å, α = 98.537(3)°, β = 107.573(2)°, γ = 106.943(3)°, V = 1036.6(1) ų, Z = 1, d _calc = 3.377 g/cm³. The crystal structure is built of trans-[{Re₆S₈}(pyz)₄I₂] cluster complexes and uncoordinated pyrazine molecules.     

A theoretical and experimental investigation of the formation of S 2 - from CS2 by electron impact

Theoretical and experimental investigation of the formation of S ₂ ^- from CS₂ by electron impact has been carried out. Molecular orbital calculations show that some of the low lying states of CS ₂ ^- have lower potential energy in the bent geometries suggesting a transformation in the geometric structure of the precursor molecular ion, leading to the formation of S ₂ ^- . In contrast to the formation of S ₂ ^- and S ₂ ^- , the kinetic energy associated with S ₂ ^- is small and disproportionate to the increase in electron energy, indicating the formation of S ₂ ^- in vibrationally excited states due to the mechanism of its formation.     

Fragmentation by electron impact ionization and intracluster reactions of size selected (N2H4) n and (OCS) n clusters

The hydrogen-bonded (N₂H₄) _n clusters and the van der Waals (OCS) _n clusters are size selected in a scattering experiment with a He beam up to the cluster sizen=6. By measuring the angular distributions of the scattered clusters the complete fragmentation pattern of electron impact ionization is obtained. For Hydrazine the two main fragment masses are the protonated species (N₂H₄) _n?1H⁺ and with somewhat weaker intensities also the nominal ion mass (N₂H₄) _n ⁺ . The largest intensity is observed for the monomer ion N₂H ₄ ⁺ to which clusters up ton=5 fragment. For carbonylsulfide, completely different results are obtained. Aside from the fragments of the OCS monomer and the van der Waals cluster fragments (OCS) ₂ ⁺ and (OCS) ₃ ⁺ signals at mass S ₂ ⁺ , S ₃ ⁺ and S₂OCS⁺ are detected. This indicates a fast chemical reaction in the cluster according to: S + OCS → CO + S₂ which occurs for clusters of sizen ≥ 2. Peaks at S ₃ ⁺ and S₂OCS⁺ are seen for the first time forn ≥ 5 according to a further reaction of S₂ in the cluster.     

Octadecylamine cobalt(III) dimethyl glyoximato complexes: synthesis,thermodynamics of micellization,steady-state photolysis and biological activities

A new class of surfactant–cobalt(III) complexes of the type trans-[Co(DH)₂(OA)X], where DH = dimethylglyoxime, OA = octadecylamine, X = Cl^?, Br^?, I^?, N₃ ^?, NO₂ ^?, SCN^? or OA, were synthesized and characterized by physicochemical and spectroscopic methods. The critical micelle concentration (CMC) values of these surfactant–cobalt(III) complexes in ethanol solution were obtained by measuring absorption at ~250 nm. Specific conductivity data (at 303–313 K) served for the evaluation of the temperature-dependent CMC and the thermodynamics of micellization (ΔG _m ⁰ , ΔH _m ⁰ and ΔS _m ⁰ ). Steady-state photolysis and cyclic voltammetry of the complexes were studied. The surfactant–cobalt(III) complexes were screened for their antibacterial and antifungal activities against various microorganisms.     

Photochemical synthesis and electronic spectra of fulminene ([6]phenacene)

Facile synthesis of fulminene ([6]phenacene) was achieved through the Mallory reaction of 1-(1-naphthyl)-2-(1-phenanthryl)ethene or the 9-fluorenone-sensitized photo-ring-closure of 1-(1-naphthyl)-2-(1-phenanthryl)ethane. The electronic spectral properties of fulminene were investigated for the first time using photoluminescence as well as transient absorption spectroscopy. The spectral features were compared with those of a series of lower phenacene homologs such as phenanthrene ([3]phenacene), chrysene ([4]phenacene), and picene ([5]phenacene). For the [n]phenacene series, both the fluorescence and phosphorescence bands linearly red-shifted with an increase in the number of the benzene rings (n). Trends in the energy levels of the excited singlet (E _S) and the triplet (E _T) states were expressed as E _s = ?2.6n + 89.1 (kcal mol^?1) and E _T = ?1.8n + 66.2 (kcal mol^?1), respectively. In the case of fulminene, laser flash photolysis displayed a transient spectrum with an absorption maximum (λ _max ^T–T ) at 675 nm, which was assigned as the triplet fulminene excited state. The λ _max ^T–T values for the [n]phenacene series showed a linear correlation as a function of the ring number n, given by an equation, λ _max ^T–T  = 60n + 318 (nm).     

A high-spin cyanide-bridged Mo6Mn9 cluster: crystal structure and magnetism

A cyanide-bridged bimetallic octacyanomolybdate(V)-based polynuclear cluster, {Mn ₉ ^II [Mo^V(CN)₈]₆(EtOH)₂₄} · 6EtOH · 3i-C₃H₇OH · 3H₂O (1), has been prepared by self-assembling of [Mo(CN)₈]^3? and Mn²⁺ ions. The compound crystallized in the trigonal system with space group R-3 and cell dimensions of a = b = 26.182(15), c = 25.586(14) Å, γ = 120°, and Z = 18. The structure of the complex consists of neutral cluster of 15 metal ions, in which all metal ions are linked by cyanide bridged ligands. Magnetic susceptibilities and magnetization measurements of the complex indicate that the cluster has an S = 39/2 ground state. The intracluster ferrimagnetic interaction has been characterized as well.     

Thermodynamic transfer functions for urea and thiourea from water to water-tetrahydrofuran mixtures from precise vapor-pressure measurements

The rate of change of the standard chemical potential with solvent composition, \(\partial \bar G_0 /\partial Z\) , has been calculated from precise vapor-pressure measurements for urea at three temperatures and for thiourea at 298.15°K in water-tetrahydrofuran (THF) mixtures. From these results the standard free energy of transfer ΔG _t ^o of the solutes from water to various water-THF mixtures has been obtained together with the standard molar entropy ΔS _t ^o and the standard molar enthalpy ΔH _t ^o of transfer at 298.15°K in the case of urea. The quantity ΔG _t ^o for urea is negative in the water-rich region and positive for mole fractions THF>0.2. There is a nearly complete compensation between ΔH _t ^o andTΔS _t ^o at 298.15°K up to mole fraction THF=0.5. These phenomena can be partly related to the structure in H₂O-THF mixtures.