Die Reaktion des Rhenium(VII)-oxides mit 1,4-Dioxan Re2O6(μ2-OH)2 · 3 C4H8O2 – ein neues Oxidhydroxid mit Metall-(1,4-Dioxan)-Bindung

Reaction of Rhenium(VII) Oxide with 1,4-Dioxane. Re₂O₆(μ₂-OH)₂ · 3 C₄H₈O₂— a Novel Oxide Hydroxide with Metal-(1,4-Dioxane) Bonds The reaction of Re₂O₇ with 1,4-dioxane in the presence of small amounts of H₂O yields the compound Re₂O₆(OH)₂ · 3(1,4-dioxane). It crystallizes in the triclinic space group P¯1 with a = 10.907(3), b = 12.875(4), c = 7.943(2) Å; α = 108.64(2), β = 103.00(2), γ = 102.29(2)°; Z = 2. The complete X-ray structure analysis (R = 2.9? ) shows the crystals to contain dimeric centrosymmetric Re₂O₆(OH)₂-units with two bridging μ₂-OH groups. The ligand spheres around Re are completed towards distorted octahedra by coordinated 1,4-dioxane molecules (one O donor per Re), the latter linking the dimeric units to endless chains. The rest of the 1,4-dioxane molecules are bonded to the OH-groups through hydrogen bridges and have no contact to Re. Mean bond distances are: Re? O(bridge) 2.065 (2.059…2.070(4)) Å, Re? O(1,4-dioxane) 2.478 (2.469 and 2.486(5)) Å, Re? O (terminal) 1.707 (1.694…1.720(5)) Å.     

Darstellung und Kristallstrukturen von (Ph3PNPPh3)2[Re2Br10] und (Ph4P)[Re2Br9]

Synthesis and Crystal Structures of (Ph₃PNPPh₃)₂[Re₂Br₁₀] and (Ph₄P)[Re₂Br₉] Depending on the molar ratio by reaction of [n-Bu₄N]₂[ReBr₆] with the Lewis acid BBr₃ in dichloromethane the bioctahedral complexes [n-Bu₄N]₂[Re₂Br₁₀] and [n-Bu₄N][Re₂Br₉] are formed. The X-ray structure determination on (Ph₃PNPPh₃)₂[Re₂Br₁₀] (monoclinic, space group C 2/c, a = 20.007(4), b = 15.456(5), c = 24.695(4) Å, β = 107.53(2)°, Z = 4) reveals a centrosymmetric edge-sharing complex anion with approximate D_2h symmetry and mean terminal and bridging Re–Br bond lengths of 2.453 (equatorial), 2.482 (axial) and 2.591 Å, respectively, and a Re–Re distance of 3.880 Å. (Ph₄P)[Re₂Br₉] (triclinic, space group P 1, a = 11.062(2), b = 12.430(3), c = 13.163(5) Å, α = 72.94(2), β = 68.47(2), γ = 82.09(2)°, Z = 2) contains a confacial bioctahedral anion with nearly D_3h symmetry and mean terminal and bridging Re–Br distances of 2.460 and 2.536 Å, respectively, and a Re–Re distance of 2.780 Å.     

μ‐Oxo‐bis{{2,2′‐[2,2‐di­methyl­propane‐1,3‐diyl­bis­(nitrilomethyl­idyne)]­diphenolato}­oxo­rhenium(V)}

The title compound, [Re₂O₃(C₁₉H₂₀N₂O₂)₂], is a hexacoordinate complex containing an [Re₂O₃]⁴⁺ core with a linear O=Re—O—Re=O bridge. The distorted octahedral coordination of the Re^V atom is achieved by an N₂O₂ donor set from the tetradentate imine–phenol ligand. The overall charge of the compound is neutral due to deprotonation of the phenol groups, and the terminating and bridging O atoms. The Re=O and Re—O bond distances of the [Re₂O₃]⁴⁺ core are 1.699 (4) and 1.911 (1) Å, respectively. The Re—O and Re—N bond distances of the equatorial plane are in the ranges 2.024 (4)–2.013 (4) and 2.128 (5)–2.120 (5) Å, respectively.     

Studies on organometallic compounds with hetero multiple bridges : V. Crystal and molecular structure of the parent rhenium complex Re2Br2(CO)6(THF)2 and substituted products of tricarbonylrhenium(I) derived from it

Reactions of the tetrahydrofuran adduct Re₂Br₂(CO)₆(THF)₂ with some phosphorous- and nitrogen-containing donors under mild conditions are reported, which led to the formation of substituted products of tricarbonylrhenium(I). Bromide abstraction from the THF adduct by secondary amines and CS₂ produced the dithiocarbamato derivatives Re(S₂CNR₂)(CO)₃(HNR₂) whose behaviour in solution with CO was also investigated. Mass spectral data for some of the substituted products have been measured. The title compound crystallizes in the space group P2₁/n with cell constants a = 8.661(2), b = 11.251(3), c = 11.424(3) Å and β = 110.36(2)°, U = 1043.67 ų and D_calc = 2.686 g cm^?3, Z = 2. The molecule consists of a planar Re₂Br₂ moiety, as demanded by symmetry. The two THF groups are on opposite sides of this plane and the three CO groups around each rhenium atom are arranged in a fac arrangement. The unique ReBr distances are 2.642(5) and 2.644(4)Å, while the ReO distance is 2.129(31) Å. The ReBrRe and BrReBr angles are 97.3(2) and 82.7(1)°, respectively. The Re?Re nonbonding distance is 3.967(3) Å. The THF ligands consist of a nearly planar C₄ fragment (maximum deviation from planarity 0.06 Å), while the oxygen is 0.348 Å out of that plane, the angle defined by the C₄ plane and the COC fragment of the THF ligand being 24.99°. Final values of the discrepancy indices are R(F) = 0.074 and R_w(F) = 0.095.     

6-Nitrohexene-1 Metathesis in the Presence of Rhenium Heterogeneous Catalysts

6-nitrohexene-1 (6-NH-1) undergoes metathesis in the presence of 16 wt.% Re₂O₇/Al₂O₃/R₄M and 3 wt.% Re₂O₇/Al₂O₃-SiO₂/R₄M (where R = methyl, ethyl; M = Sn or Pb) catalysts. The system containing alumina as a support is more active. Tetramethyltin (TMT) and tetraethyllead (TEL) used as co-catalysts, exhibited similar activating effect which was greater than with tetraethyltin (TET). The best results were obtained when the Re:Sn(Pb) and 6-NH-1:Re ratios were equal, respectively, to 1:1 and 10:1. The alumina-silica supported catalysts activity can be enhanced by doping the support with very small amounts of molybdenum ions.     

Preparation and Crystal Structure of PbRe2O6. An Example of the Re2O10 Unit with No Metal-Metal Bonding

Single crystals of PbRe₂O₆ were obtained from a stoichiometric mixture of PbO and ReO₃ at 500°C. The structure was determined by Patterson methods from X-ray four-circle diffractometer data using 2 270 (392 unique) reflections; R_W(F) = 0.036. PbRe₂O₆ crystallizes in the trigonal space group R3m with a = 10.359(6) Å, c = 11.092(6) Å and Z = 9. The compound is isotypic with the trigonal modification of PbNb₂O₆ and contains an Re₂O₁₀ unit. Unlike other compounds containing this species, there is no metal-metal bonding.     

Ein Polyphosphid mit Rhenium-Clustern: Synthese und Kristallstruktur von Re6P13

A Polyphosphide with Rhenium Clusters: Synthesis and Crystal Structure of Re₆P₁₃ Microcrystalline Re₆P₁₃ was prepared by heating the elemental components in the presence of iodine. Single crystals were obtained by reaction of the components in molten tin. They are rhombohedral, R3 , with the hexagonal cell dimensions: a = 15.665(9), c= 8.320(2) Å, Z = 6. The structure was determined and refined from single-crystal data(R = 0.053). The Re atoms are coordinated by six P atoms in distorted octahedral configuration. Four edge-sharing octahedra are distorted in such a way that Re? Re bonds (2.76 to 2.94 Å) are formed. All P atoms are tetrahedrally coordinated by Re and P atoms. The P atoms form six-membered rings, four membered chains, and pairs. One P atom has only Re neighbors. The crystal structure of Re₆P₁₃ is discussed together with the structures of related compounds.     

Synthesis and Crystal Structure of (PCl4)[Re2Cl9]

The reaction between PCl₃ and ReCl₅ yielded at 200 °C the ionic tetrachlorophosphonium dirhenium nonachloride, (PCl₄)[Re₂Cl₉]. Single crystal X-ray diffraction analysis revealed a monoclinic unit cell: a = 8.616(3) Å, b = 10.449(4) Å, c = 9.397(3) Å, β = 99.72(3)°, V = 833.9(5) ų, Z = 2, sp. gr. P2₁/m, wR₂ = 0.1083 and R₁ = 0.0527. The ionic compound is built from tetrahedra PCl₄⁺ and face-sharing bioctahedra Re₂Cl₉^–. The Re–Re distance, 2.724 Å, indicates the presence of direct Re-Re interaction.     

Difluorotetrakis(2‐oxypyridine)dirhenium(III) – Preparation,Crystallographic Structure,and Electrochemical Properties

The solid‐state‐melt reaction of (NH₄)₂[Re₂F₈] · 2H₂O with 2‐hydroxypyridine (2‐HOpy) produced dark‐red Re₂(2‐Opy)₄F₂ ( 1 ). This air‐stable compound was obtained in crystalline form as 1· CHCl₃. It was characterized in the solid state by single‐crystal X‐ray diffraction and in solution by UV/Vis spectroscopy and cyclic voltammetry. 1· CHCl₃ forms triclinic crystals with α = 8.3254(5) Å, b = 8.5563(5) Å, c = 11.6784(8) Å, α = 82.723(3)°, β = 75.769(3) °, γ = 64.407(2) °. The Re–Re and Re–F distances were 2.2091(7) and 2.115(6) Å, respectively. The molecule is isostructural with the corresponding chloro derivative.     

Ambidentate coordination of the tripyridyl ligands 2,2′:6′,2″-terpyridyl,tris(2-pyridyl)-amine,tris(2-pyridyl)methane and tris(2-pyridyl)phosphine to carbonylrhenium centres: Structural and spectroscopic studies

The reactions of [Re(CO)₅Cl] with the ligands tpy (2,2′:6′,2″-terpyridine), py₃N {tris(2-pyridyl)-amine}, py₃CH {tris(2-pyridyl)methane}, and py₃P {tris(2-pyridyl)phosphine} in toluene solution realize compounds with the general formulation [Re(ligand)(CO)₃Cl] in which the tripyridyl ligands are bidentate. X-ray structural determinations of fac-[Re(typ)(CO)₃Cl].H₂O and fac-[Re(py₃N)(CO)₃Cl] confirm these assignments. [Re(tpy)(CO)₃Cl].H₂O (C₁₈H₁₃ClN₃O₄Re) is monoclinic, space group P2₁/n, with cell dimensions a = 7.432(2) Å, b = 17.016(4) Å, c = 14.466(2) Å, β = 93.51(2)°, and Z = 4; full-matrix least-squares refinement on 2435 reflections with I ? 2.5σ(I) converged to a final R = 0.028 and R_w = 0.029. [Re(py₃N)(CO)₃Cl] (C₁₈H₁₂ClN₄O₃Re) is triclinic, space group P1 with cell dimensions a = 13.761(2) Å, b = 14.636(6)Å, c = 11.110(2) Å, α = 110.70(2)°, β = 102.45(2)°, γ = 107.48(2)°, and Z = 4; full-matrix least-squares refinement on 3459 reflections with I ? 2.5σ(I) converged to a final R = 0.038 and R_w = 0.039. If the synthetic procedure is undertaken under irradiation by visible light, for the ligand py₃N a species [Re(py₃N)(CO)₂Cl] (characterized by infrared spectroscopy and conductance measurements) is also formed, in which the ligand py₃N is tridentate. No analogous tridentate species is formed with the ligands tpy or py₃P, although there is evidence that it also forms for py₃CH.     

Synthesis and Properties of Rb6Mn2O6

Rb₆Mn₂O₆ was prepared via the azide/nitrate route. Stoichiometric mixtures of the precursors (Mn₃O₄, RbN₃ and RbNO₃) were heated in a special regime up to 500 °C and annealed at this temperature for 75 h in silver crucibles. Single crystals have been grown by annealing a mixture with a slight excess of rubidium components at 450 °C for 500 h. According to the single crystal structure analysis, Rb₆Mn₂O₆ is isotypic to K₆Mn₂O₆, and crystallizes in the monoclinic space group P2₁/c with a = 6.924(1) Å, b = 11.765(2) Å, c = 7.066(1) Å, β = 99.21(3)°, 2296 independent reflections, R₁ = 5.23 % (all data). Manganese is tetrahedrally coordinated and two tetrahedra are linked by sharing a common edge, forming a dimer [Mn₂O₆]⁶⁻. The magnetic behavior has been investigated.     

Rhenium(I) Tellurolate,Telluroether and Bidentate-Telluroether Complexes: Crystal Structures of Re(CO)3Br(PhTe(CH2)3TePh), PhTeRe(CO)5 Re2(μ-SePh)2(CO)8 and [(PhTeMe)Re(CO)5][BF4]

The monomeric rhenium(I) complex with bidentate telluroether ligand Re(CO)₃Br(PhTe(CH₂)₃TePh) (1) was accessible via reaction of the PhTe(CH₂)₃TePh with Re(CO)₅Br. This chelate complex crystallized in triclinic space group $ {\rm P}\bar 1 $ with a = 9.390(5) Å, b = 10.961(3) Å, c = 11.849(4) Å a = 63.30(3)°, β = 87.49(4)° γ = 69.31(4)°, V = 1009.5(7) ų Z = 2, R = 0.033, and R_w = 0.034. Reaction of Re(CO)₅Cl with NaTePh yielded the Re(I) specics PhTeRe(CO)₅ (2). This complex crystallized in triclinic space group $ {\rm P}\bar 1 $ with a = 7.085(1) Å, b = 9.203(1) Å, c = 11.341(1) Å, α = 107.24(1)°, β = 100.56(1)°, γ = 96.47(1)°, V = 683.2(2) ų, Z = 2, R = 0.027, R_w = 0.022. Reaction of PhTeRe(CO)₅ and (PhSe)₂ in THF at 65 °C yielded a product that was confirmed crystallographically to be the known species Re₂(μ-SePh)₂(CO)₈ (3), in which two phenylselenolate ligands bridge the two Re(I). Compound 3 crystallized in monoclinic space group P2₁/n with a = 7.210(2) Å, b = 18.862(6) Å, c = 9.083(3) Å, β = 107.48(3)° V = 1178.2(7) ų, Z = 2, R = 0.046, and R_w = 0.051. Methylation of PhTeRe(CO)₅ with [Me₃O][BF₄] afforded Re(I) product [(PhTeMe)Re(CO)₅][BF₄] (4). This monodentate telluroether species crystallized in monoclinic space group P2₁/n with a = 8.405(1) Å, b = 13.438(3) Å, c = 15.560(2) Å, β = 92.59(1)° V = 1755.5(5) ų, Z = 4, R = 0.035, and R_w = 0.035.     

Preparation and Crystal Structure of Rare Earth Rhenates: the Series Ln5Re2O12 with Ln = Y,Gd–Lu,and the Praseodymium Rhenates Pr3ReO8, Pr3Re2O10, and Pr4Re2O11

The crystal structure of the known compounds Ln₅Re₂O₁₂ (Ln = Y, Gd, Dy–Lu) and the new isotypic terbium rhenate Tb₅Re₂O₁₂ was determined from X‐ray data of a twinned crystal of Ho₅Re₂O₁₂: B2/m, a = 1236.5(4) pm, b = 748.2(2) pm, c = 563.8(1) pm, γ = 107.73(3)°, Z = 2, R = 0.034 for 379 structure factors and 37 variable parameters. The rhenium atoms (oxidation number +4.5) have octahedral oxygen coordination. These ReO₆ octahedra share edges, thus forming infinite strings with alternating short and long Re–Re distances: 243.6(2) and 320.1(2) pm. Of the three holmium positions two are surrounded by seven oxygen atoms and the third one has octahedral oxygen coordination. The crystal structure of Pr₃ReO₈ was refined from single‐crystal X‐ray data: P2₁/a, a = 1498.0(2) pm, b = 749.09(8) pm, c = 610.48(9) pm, γ = 110.39(1)°, R = 0.017 for 2082 F values and 110 variable parameters. It is isotypic with a structure first determined for Sm₃ReO₈. The new compounds Pr₃Re₂O₁₀ and Pr₄Re₂O₁₁ were prepared by reaction of elemental praseodymium with the metaperrhenate Pr(ReO₄)₃. They were characterized through their X‐ray powder diagrams. Pr₃Re₂O₁₀ was found to be monoclinic: a = 778.47(9) pm, b = 773.62(9) pm, c = 706.10(8) pm, β = 114.77(1)°. It is isotypic with La₃Os₂O₁₀ and La₃Re₂O₁₀. Pr₄Re₂O₁₁ crystallizes with Nd₄Re₂O₁₁ type structure with the tetragonal lattice constants a = 1272.49(3) pm, c = 562.29(2) pm. The compounds Nd₄Re₂O₁₁ and Sm₄Re₂O₁₁ are confirmed. The magnetic properties of Ho₅Re₂O₁₂, Tb₅Re₂O₁₂, Pr₃Re₂O₁₀, Pr₄Re₂O₁₁, Nd₄Re₂O₁₁, and Sm₄Re₂O₁₁ were investigated with a Faraday balance. None of these compounds shows magnetic order above 200 K.     

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.     

ReV‐Phthalocyaninate und ReV‐Tetraphenylporphyrinate mit Oxo‐Liganden: Synthese,Eigenschaften und Kristallstruktur

Re^V‐Phthalocyaninates and Re^V‐Tetraphenylporphyrinates: Synthesis, Properties, and Crystal Structure Hexa‐coordinated Re^V phthalocyaninates (pc) and Re^V tetraphenylporphyrinates (tpp) of the type [Re(O)(X)p] (p: pc, tpp) with X = OCH₃, ReO₄, Cl/pc, F/pc, OH/tpp, [{Re(O)p}₂(μ‐O)] and (cat)^trans[Re(O)₂p] (cat: ⁿBu₄N, Et₄N/tpp) have been isolated and characterised by their UV‐Vis‐NIR, IR and resonance Raman (RR) spectra. In the RR spectra, the intensity of the (Re=O) and (Re–X) stretching vibrations (ν(Re=O/–X)) in [Re(O)(X)p] and [{Re(O)p}₂(μ‐O)] is selectively enhanced with excitation in coincidence with O → Re–CT between ca 19000 and 22000 cm^–1. In accordance to selection rules, data of ν(Re=O/–X) compare well with those of the complementary IR spectra. Because of the trans influence ν(Re=O) depends on the axial ligand X, ranging from 940 to 1010 cm^–1. The crystallographic characterization of [Re(O)(ReO₄)tpp] · CHCl₃ ( 1 ), [{Re(O)tpp}₂(μ‐O)] · py ( 2 ), (ⁿBu₄N)^trans[Re(O)₂tpp] ( 3 ), and (Et₄N)^trans[Re(O)₂tpp] · 2 H₂O ( 4 ) is described. The tpp centered Re atom is in a distorted octahedron of four N atoms of the porphyrinate and two axial O atoms in a mutual trans position. Average Re–N distances are 2.062 Å in 1 , 2.086 Å in 2 , 2.089 Å in 3 , and 2.082/2.086 Å in 4 . The Re–O distance of the terminal rhenyl group varies from 1.64(1) Å ( 1 ), 1.73(1)/1.70(1) Å ( 2 ) to 1.80(1) Å ( 4 ), that of the monodentate rhenate(VII) from 1.70(1) to 1.75(1) Å. The Re–O distances in the bridge of the linear O=Re–O–Re=O skeleton in 2 are 1.95(1)/1.89(1) Å. In 1 , with a bent O=Re–O^ ReO₃ moiety (∢(Re–O^ReO₃) = 143(1)°) and a mostly ionic coordinated rhenate(VII), these distances differ significantly (2.20(1) Å vs 1.75(1) Å). The porphyrinate in 1 is saucer‐shaped with a distal rhenate(VII), and the tpp centered Re atom is displaced by 0.31 Å out of the (N)₄ plane towards the rhenyl‐O atom. The distorted porphyrinates in 2 are rotated by 30.4(4)°, and the Re atoms are 0.1 Å out of their (N)₄ planes towards the terminal O atoms. In 3 and 4 the porphyrinates are almost planar with the Re atom in their centre.     

Zur Reaktion des Rhenium(VII)-oxids mit 1,4-Dioxan – Kristallstruktur von Re2O7(OH2)2 · 2(1,4-Dioxan)

Reaction of Rhenium(VII) Oxide with 1,4-Dioxane – Crystal Structure of Re₂O₇(OH₂)₂ · 2(1,4-Dioxane) By solvolysis of polymeric Re₂O₇ with 1,4-dioxane in the presence of small amounts of H₂O two products of compositions Re₂O₆(OH)₂ · 3(1,4-dioxane) ( 1 ) and Re₂O₇ · 2H₂O · 2(1,4-dioxane) ( 2 ) are formed. From a complete X-ray single-crystal structure analysis 2 could now be characterized structurally (monoclinic, space group P2₁/c, a = 6.828(3) Å, b = 9.530(2) Å, c = 26.421(8) Å, β = 91.71(3)°, Z = 4). The compound is important as a convenient precursor for the preparation of pure rhenium trioxide. It is to be formulated as Re₂O₇(OH₂)₂ · 2(1,4-dioxane) and contains, contrary to 1 , no 1,4-dioxane coordinated to Re. The crystalline phase consists of a supramolecular arrangement of Re₂O₇(OH₂)₂ units as in “solid perrhenic acid” and of 1,4-dioxane molecules associated through O? H …? O hydrogen bridges. Analogous to dirhenium heptoxide and to solid perrhenic acid one of the rhenium atoms is in tetrahedral, the other is in distorted octahedral coordination.     

The preparation and crystal structures of BiReO4 and BiRe2O6

The crystal structures of two new oxides, BiReO₄ and BiRe₂O₆, have been determined by single-crystal X-ray methods using an Enraf-Nonius CAD-4F diffractometer. BiReO₄ crystallizes as red metallic needles in the space group Cmcm, cell dimensions a = 3.839(1) Å, b = 14.914(2) Å, c = 5.534(1) Å, Z = 4. The structure consists of sheets of corner-shared octahedra (composition ReO₄) linked by Bi atoms (R = 2.55%). BiRe₂O₆ crystallizes as black metallic plates in the space group C2/m, cell dimensions a = 5.516(1) Å, b = 4.906(1) Å, c = 8.384(1) Å, β = 106.71(1)°, Z =2. The structure consists of layers containing Re₂O₁₀ units linked together by corner sharing of the octahedra, alternating with layers of Bi atoms (R = 2.61%). The structure is disordered due to the random stacking of the Re layers. The Re---Re distance of 2.5 Å in the Re₂O₁₀ unit is comparable to that found in similar compounds. Both compounds exhibit stereochemically active lone pairs.     

[ReIII(thiourea-S)6]Cl3 · 4 H2O and [ReIII(N-methylthiourea-S)6]Cl3 as Precursors to other ReIII Complexes: a Kinetic Study in Aqueous Media. Crystal Structure of [ReIII(N-methylthiourea-S)6](PF6)3 · H2O

Capability of [Re^III(tu-S)₆]Cl₃, where tu = thiourea, as a precursor to other Re^III complexes by ligand substitution in aqueous medium is studied. For the decomposition of [Re(tu-S)₆]Cl₃, experiments suggest pseudo first order kinetics and observed rate constants vary from 1.3 × 10^–2 to 9.6 × 10^–2 min^–1 in the pH range 2.80–5.04. Experiments in presence of incoming ligand (ethylendiaminetetraacetic acid or diethylentriaminepentaacetic acid) show that ligand substitution is significantly slower than decomposition of the precursor, even when pH and temperature are modified. Similar results were obtained working with [Re^III(Metu-S)₆]Cl₃, where Metu = N-methylthiourea. Molecular structure of [Re^III(Metu-S)₆](PF₆)₃ · H₂O was determined by single crystal X-ray diffractometry. The coordination polyhedron around the Re ion is a distorted octahedron. The six methylthiourea ligands are bonded to the metal through the sulfur atoms [bond lengths range from 2.409(2) to 2.451(2) Å].     

Alkoxo‐Verbindungen des dreiwertigen Eisen: Synthese und Charakterisierung von [Fe2(OtBu)6], [Fe2Cl2(OtBu)4], [Fe2Cl4(OtBu)2] und [N(nBu)4]2[Fe6OCl6(OMe)12]

Alkoxo Compounds of Iron(III): Syntheses and Characterization of [Fe₂(OtBu)₆], [Fe₂Cl₂(OtBu)₄], [Fe₂Cl₄(OtBu)₂] and [N(nBu)₄]₂[Fe₆OCl₆(OMe)₁₂] The reaction of iron(III)chloride in diethylether with sodium tert‐butylat yielded the homoleptic dimeric tert‐‐butoxide Fe₂(OtBu)₆ ( 1 ). The chloro‐derivatives [Fe₂Cl₂(OtBu)₄] ( 2 ), and [Fe₂Cl₄(OtBu)₂] ( 3 ) could be synthesized by ligand exchange between 1 and iron(III)chloride. Each of the molecules 1 , 2 , and 3 consists of two edge‐sharing tetrahedrons, with two tert‐butoxo‐groups as μ₂‐bridging ligands. For the synthesis of the alkoxides 1 , 2 , and 3 diethylether plays an important role. In the first step the dietherate of iron(III)chloride FeCl₃(OEt₂)₂ ( 4 ) is formed. The reaction of iron(III)chloride with tetrabutylammonium methoxide in methanol results in the formation of a tetrabutylammonium methoxo‐chloro‐oxo‐hexairon cluster [N(nBu)₄]₂[Fe₆OCl₆(OMe)₁₂] ( 5 ). Crystal structure data: 1 , triclinic, P1¯, a = 9.882(2) Å, b = 10.523(2) Å, c = 15.972(3) Å, α = 73.986(4)°, β = 88.713(4)°, γ = 87.145(4)°, V = 1594.4(5) ų, Z = 2, d_c = 1.146 gcm^—1, R₁ = 0.044; 2 , monoclinic, P2₁/n, a = 11.134(2) Å, b = 10.141(2) Å, c = 12.152(2) Å und β = 114.157(3)°, V = 1251.8(4) ų, Z = 2, d_c = 1.377 gcm^—1, R₁ = 0.0581; 3 , monoclinic, P2₁/n, a = 6.527(2) Å, b = 11.744(2) Å, c = 10.623(2), β = 96.644(3)°, V = 808.8(2) ų, Z = 2, d_c = 1.641 gcm^—1, R₁ = 0.0174; 4 , orthorhombic, Iba2, a = 23.266(5) Å, b = 9.541(2) Å, c = 12.867(3) Å, V = 2856(2) ų, Z = 8, d_c = 1.444 gcm^—1, R₁ = 0.0208; 5 , trigonal, P3₁, a = 13.945(2) Å, c = 30.011(6) Å, V = 5054(2) ų, Z = 6, d_c = 1.401 gcm^—1; R_c = 0.0494.     

Crystal structure of K6CrNb15O42

K_6CrNb_(15)O_(42)crystallizes in the hexagonal system with a=9.126(3)A,c=12.068(3)A,V=870.4(5)A~3,and space group P6_2/mcm,Z=1.The structure was solved using direct method andFourier Techniques.Of the 829 unique reflections measured by counter techniques,448 with I≥3σ(I)were used in the least-squares refinement of the model to R=0.034(R_w=0.044).The structureof KoCrNb_(15)O_(42)may be described as consisting of corner-shared and edge-shared octahedra,the ringunits composed of six octahedra of Nb(1)are corner-shared one another along the c-axis to formhexagonal column octahedra chains which are connected by K~+ and octahedra of Nb(2).