Drei Wege zur Oxydation von [Ta6Cl12]2+ ([Ta6Br12]2+ und [Nb6Cl12]2+)

Three Oxidation Paths of [Ta₆Cl₁₂]²⁺ ([Ta₆Br₁₂]²⁺ and [Nb₆Cl₁₂]²⁺) [Ta₆Cl₁₂]²⁺ is oxidized autocatalytically to [Ta₆Cl₁₂]⁴⁺ by HNO₃. The titration of [Ta₆Cl₁₂]²⁺ with KBrO₃ (in HBr-containing solutions) or with Ce⁴⁺ or K₂Cr₂O₇ (in HNO₃-containing solutions) leads to a clear [Ta₆Cl₁₂]³⁺ step. The further titration leads beside [Ta₆Cl₁₂]⁴⁺ to the formation of Ta₂O₅(· xH₂O). [Ta₆Cl₁₂]²⁺ behaves with KBrO₃(+ HBr) equally, but the formation of [Ta₂O₅](· xH₂O) is only small. [Nb₆Cl₁₂]²⁺ (22°C) titrated with Ce(ClO₄)₄ in 2n HClO₄ gives the first potential step nearby exact ([Nb₆Cl₁₂]³⁺) and at a very slow titration in a second step a precipitation of Nb₂O₅(· xH₂O) occurs, which adsorbed Ce⁴⁺ additionally. At ?15°C with Ce(ClO₄)₄ the first potential step was exactly at [Nb₆Cl₁₂]^2+→3+, while the second step needs a distinct additional consumption of titer. (Formation of [Nb₆Cl₁₂]⁴⁺ and beside it [Nb₂O₅](· xH₂O)). From the titration curves and sections of its normal progress in all cases we get the normal potentials 2+/3+ and 3+/4+ with an accuracy of ± 0.01 volt. In alkaline solution the complexes are oxidized with air-oxygen to [M₆X₁₂](OH)₆^2?, while the Br-containing complexes suffer hydrolysis afterwards.     

Electronic structure and bonding of the metal cluster compound Au55(PPh3)12Cl6

We discuss the electronic structure, bonding and physical properties of the gold cluster compound Au₅₅(PPh₃)₁₂Cl₆. Results from our experimental measurements, including EXAFS, specific heat, Mössbauer, UV-visible and photoelectron spectroscopy, are combined with those of other work to form a consistent physical picture of the system. The bonding in Au₅₅(PPh₃)₁₂Cl₆ is much more delocalised and non-directional than in smaller gold cluster molecules. The Au₅₅ cluster exhibits a substantial degree of metallic bonding, while displaying some of the characteristics of a discrete energy level spectrum.     

Thiocyanate Compounds of [Nb6Cl12]2+: The structure of A4[Nb6Cl12(NCS)6](H2O)4 (A = K,Rb, NH4)

New compounds of the general formula A₄[Nb₆Cl₁₂(NCS)₆](H₂O)₄ (A = K, Rb, NH₄) were synthesized from Nb₆Cl₁₄ and ASCN in aqueous solutions. X-ray structure refinements were performed on single-crystal data of the three compounds. They are isotypic and crystallize with the space group P1 (Z = 1) and the lattice parameters: a = 877.9(3) pm, b = 1176.6(3) pm, c = 1187.0(3) pm, α = 114.29(1)°, β = 98.96(2)°, γ = 100.91(2)° for K₄[Nb₆Cl₁₂(NCS)₆](H₂O)₄ ( 1 ); a = 887.6(3) pm, b = 1184.0(4) pm, c = 1195.4(4) pm, α = 114.95(2)°, β = 98.84(2)°, γ = 101.31(2)° for Rb₄[Nb₆Cl₁₂(NCS)₆](H₂O)₄ ( 2 ) and a = 886.0(4) pm, b = 1181.1(6) pm, c = 1183.9(6) pm, α = 114.49(2)°, β = 99.48(3)°, γ = 101.53(1)° for (NH₄)₄[Nb₆Cl₁₂(NCS)₆](H₂O)₄ ( 3 ). Each centrosymmetric [Nb₆Cl₁₂(NCS)₆]^4? ion of the isotypic compounds contains six terminal thiocyanate groups being bound to the corners of the octahedral niobium cluster through the nitrogen atoms (d_{Nb? N} = 221.5(6)–224.3(6) pm, bond angles Nb? N? C 168.6(5)–176.4(6)°). The [Nb₆Cl₁₂(NCS)₆]^4? ions are linked via A? S and A? Cl interactions with the A cations. Half of the cations occur to be disordered along two crystallographic sites.     

Einzentrenmodell für die Clusterverbindung [Nb6Cl12]4+

The electronic ground state of [Nb₆Cl₁₂]⁴⁺ is calculated using a one-center-model. One obtains the observed diamagnetic character.     

Octahedral metal clusters as building units in a neutral layered honeycomb network, [Zn(en)]2[Nb6Cl12(CN)6

A polymeric hybrid cluster-based compound with a double-layered honeycomb framework built of octahedral niobium cyanochloride clusters and [Zn(en)]2+ metal complexes was designed and synthesized at room temperature, and structurally characterized by single crystal X-ray diffraction.     

Straightforward synthesis and structure of a new starting material for niobium cluster phases: [Nb6Cl(i)12(CH3OH)a4Cla2].6CH3OH

A new, fast, and straightforward synthetic route for the new cluster compound [Nb(6)Cl(i)(12)(CH(3)OH)(a)(4)Cl(a)(2)].6CH(3)OH, taking advantage of the special solubility properties of tetracyanoborate salts has been established, and the single-crystal X-ray structure of this compound, which is a promising starting material for new cluster phases, has been determined.     

A new quasi-one-dimensional niobium oxychloride cluster compound Cs2Ti4Nb6Cl18O6: structural effects of ligand combination

The new niobium oxychloride cluster compound, Cs2Ti4Nb6Cl18O6, was obtained by solid-state synthesis techniques in the course of our systematic investigation of metal oxychloride systems aimed at the preparation of low-dimensional cluster compounds. Cs2Ti4Nb6Cl18O6 crystallizes in the trigonal system, with unit cell parameters a= 11.1903(7), c = 15.600(2) A, space group P3bar1c, Z = 2. Its crystal structure was determined by single-crystal X-ray diffraction techniques. The full-matrix least-squares refinement against F(2) converged to R(1) = 0.048 (F(o) > 4sigma(F(o))), wR(2) = 0.069 (all data). The structure is based on an octahedral cluster unit (Nb6Cl(i)6O(i)6)Cl(a)6 in which the six edge-bridging oxide ligands are arranged in two sets of three on opposite sides of the Nb6 octahedron. Ti(3+) ions link the clusters through O(i) and Cl(a) ligands to form linear chains running along the c axis. The location of titanium ions correlates with the arrangement of oxide ligands around the Nb6 metal core. The chains interact with each other through additional Ti(3+) and Cs(+) ions. Interchain interactions are significantly weaker than intrachain interactions, resulting in a quasi-one-dimensional character of the overall structure.     

The oxychlorides in Nb6 cluster chemistry

The Nb₆ oxychlorides based on Nb₆L₁₈ units that we have isolated, as well as another one recently reported in the literature, are reviewed. Each of them is structurally described through a relevant example: Cs₂LuNb₆Cl₁₇O, Cs₂UNb₆Cl₁₅O₃, ScNb₆Cl₁₃O₃, Ti₂Nb₆Cl₁₄O₄ and KLu₃Nb₆Cl₁₅O₆, the structure of the latter has just been solved. They are discussed by comparison with the Nb₆ chlorides and Nb₆ oxides, considering the electronic and steric evolution of the Nb₆L₁₈ unit upon increasing O/C1 ratio. The environments of the trivalent cations will be compared, specially those involving extra halogens in KLu₃Nb₆Cl₁₅O₆ and Ti₂Nb₆Cl₁₄O₄.     

Structural studies of indium and thallium insertion into the framework of the cluster compound Ti2Nb6Cl14O4

We have investigated the possibility of altering the electronic configuration of the niobium oxochloride cluster compound Ti2Nb6Cl14O4 (I) by doping this material with monovalent cations that can fit into cavities present in its cluster framework. The doping of I with In+ and Tl+ ions resulted in the formation of MxTi2Nb6Cl14-xO4+x (M = In, x = 0.10, 0.20, 0.27; M = Tl, x = 0.10, 0.20) in which the M+ ions partially occupy these cavities. The crystal structure analysis indicated that the additional charge provided by M+ ions is compensated by substitution of chlorine by oxygen, which leads to the cluster electronic configuration being intact. Crystal data: In0.272Ti2Nb6Cl13.728O4.272, space group C2/c (No. 15), a = 12.679(2) A, b = 14.567(2) A, c = 12.632(3) A, beta = 95.26(2) degrees, Z = 4; Tl0.196Ti2Nb6Cl13.804O4.196, space group C2/c (no. 15), a = 12.732(1) A, b = 14.607(2) A, c = 12.662(2) A, beta = 95.28(1) degrees, Z = 4.     

Die Massenspektren von Pd6Cl12, Pt6Cl12 und PdnPt6−nCl12

Mass Spectra of Pd₆Cl₁₂, Pt₆Cl₁₂, and Pd_nPt_6?nCl₁₂ Pd₆Cl₁₂, and Pt₆Cl₁₂ and both together are volatilised in a mass spectrometer. 3 Cl and 1 Pd have approximately the same mass, therefore isotopes of Pd and Pt are used (¹⁰⁸Pd, ₁₉₄Pt). With an ionisation energy of 50 eV part of the vapourised molecules is strongly fragmented. With a lower ionisation energy the molecule ions Pd₆Cl₁₂⁺, Pt₆Cl₁₂⁺ and Pd_nPt_6?nCl₁₂⁺ are only observed.     

Zur Kenntnis von Ba6Ru2PtO12Cl2

About Ba₆Ru₂PtO₁₂Cl₂ Single crystals of Ba₆Ru₂PtO₁₂Cl₁₂ were prepared by a BaCl₂ flux and investigated by X-ray methods (D? P3 M1; a = 5,805; c = 15.006 Å; Z = 1). The characteristic face shared M₃O₁₂-octahedratriples show an ordered (Ru/Pt/Ru) occupation. Calculation of the Coulomb term of lattice energy support the charge distribution (5⁺/4⁺/5⁺) ions engage three point sites with different coordinations. The connection to other compounds are discussed.