Dark Blue Crystals Research Articles

New Binuclear Copper Complexes [(9S3)Cu(CN)Cu(9S3)]Xn (X=BF4, n=1; X=TCNQ, n=2) (9S3=1, 4, 7‐trithiacyclononane): Syntheses, Crystal Structures and Magnetic Properties

AbstractThe binuclear Cu complex salts of 1, 4, 7‐trithiacyclononane (9S3) with an inorganic anion (BF4)‐ and with an organic radical anion TCNQ‐ (7, 7′, 8, 8′‐tetracyanoquinodimethanide) were synthesized and their molecular and crystal structures were examined in connection with the magnetic properties. The new complex cation [Cu(9S3)CN(9S3)Cu]+ varies its charges and magnetic properties depending on the counter anions; [Cu(9S3)CN(9S3)Cu](BF4) (1) was obtained as diamagnetic colorless crystals, while [Cu(9S3)CN(9S3)Cu](TCNQ)2 (2) was obtained as dark blue crystals with antiferromagnetic properties. Complex 1 crystallized in the monoclinic space group C2/c with a = 26.863(2), b = 7.0878(5), c = 13.4864(8) Å, β = 116.318(2)°. Complex 2 crystallized in the triclinic space group P1¯ with a = 12.521(1), b = 20.2698(8), c = 8.0205(4) Å, α = 100.688(4), β = 93.846(5), γ = 94.953(4)°. Both complexes are comprised of cyano‐bridged two Cu(9S3) ions with tetrahedral coordination. The X‐ray structural study revealed that 1 has two crystallographically equivalent copper(I) atoms, while 2 has two crystallographically independent CuI/II sites. The two CuI/II sites could not be distinguished from the X‐ray structural study. For 2 the IR spectra show that both crystallographically independent TCNQ species were monoanions and are strongly dimerized due to π‐stacking, which well explains their diamagnetic contribution to the magnetic susceptibility and the highly insulating property of this salt. The temperature‐dependent magnetic susceptibility of 2 showed a deviation from the Curie‐Weiss behaviour around 60 K, which indicates a strong antiferromagnetic intermolecular interaction between the copper complexes and that such intermolecular interaction should partly occur via the TCNQ radical anion dimer.

Syntheses and Crystal Structures of the Two New Polychalcogenides [Mn(C6H14N2)3]Se6 and [Mn(C6H14N2)3]2[C6H16N2](TeSe2)2Se

The solvothermal reaction of MnCl2·4 H2O, K2Se3 and Se in trans-cyclohexane-1,2-diamine (chxn) at 433 K yields dark blue crystals of [Mn(chxn)3]Se6 (1), and the reaction of MnCl2 ・4 H2O, K2Se3 and Te under similar conditions gives dark blue crystals of [Mn(chxn)3]2[H2chxn](TeSe2)2Se (2). While compound (1) crystallises in the orthorhombic space group Pbcn with the lattice parameters a = 13.7017(9), b = 19.9073(8) and c = 10.8058(5)Å , compound (2) crystallises in the monoclinic space group P21 with the lattice parameters a = 9.4396(6), b = 24.2450(2), c = 12.8170(8) Å and β =91.6(1)◦. In both structures discrete complex cations and polychalcogenide anions are found. In (1) the Se6 2− anions form a pseudo-layer arrangement with nearly rectangular pores. The complex cations are encapsulated by the arrangement of the Se6 2− anions. Some short distances between the amino groups of the ligands and the anions indicate weak hydrogen bonding. In compound (2) two independent [Mn(chxn)3]2+ and one unique H2chxn dications, two unique TeSe2 2− as well as one Se2− dianion coexist. The two complex cations exhibit different conformations. One of the two TeSe2 2− anions has the di-protonated chxn molecule in the neighbourhood and short Se···H separations indicate weak hydrogen bonding. The isolated Se2− ion is located above the ring of the di-protonated trans-cyclohexane-1,2-diamine molecule and again a short Se···H separation may be due to a weak hydrogen bond. Compound (1) decomposes in a single step when heated in an Ar atmosphere. In contrast, the thermal decomposition of compound (2) is complex and at least five different steps can be identified.

Defects in Anatase TiO2Single Crystal Controlled by Heat Treatments

Optical absorption and electron paramagnetic resonance (EPR) spectra were measured for synthetic anatase TiO 2 single crystals annealed under oxygen or hydrogen atmosphere at the desired temperatures. The as-grown crystal changed its color from pale blue through yellow to colorless by annealing under oxygen pressure. On the other hand, the contact of the colorless crystal with hydrogen gas resulted in the change of its color to pale blue or dark blue depending on annealing temperature. On repetitive heat-treatment under oxygen atmosphere, the dark blue crystal became dark green, yellow and colorless. Since the change of the crystal colors reflects difference in the defect states, repetitive control of the defect states was established in this work. The EPR spectra revealed absence of paramagnetic species in colorless crystal and presence of the conduction electrons in pale blue, dark blue and dark green crystals. The EPR spectra of pale blue crystal were asymmetric because of the existence of conduction e...

Crystal structure of triaquasulfato-2,3-diaza-1,6-di(4-fluorobenzyl)-hexanecopper(II) dihydrate, Cu(C16H18N2F2)(H2O)3(SO4) · 2H2O

Abstract C16H28CuF2N2O9S, monoclinic, P121/c1 (No. 14), a = 15.169(8) Å, b = 12.614(6) Å, c = 11.387(6) Å, β = 94.651(7)°, V = 2171.6 Å3, Z = 4, Rgt(F) = 0.046, wRref(F2) = 0.138, T = 298 K.

Macrocyclic copper(II) and zinc(II) complexes incorporating phosphate esters.

Slow evaporation of solutions prepared by adding either Cu(ClO(4))(2).6H(2)O or Zn(ClO(4))(2).6H(2)O to solutions containing appropriate proportions of Me(3)tacn (1,4,7-trimethyl-1,4,7-triazacyclononane) and sodium phenyl phosphate (Na(2)PhOPO(3)) gave dark blue crystals of [Cu(3)(Me(3)tacn)(3)(PhOPO(3))(2)](ClO(4))(2).(1)/(2)H(2)O (1) and colorless crystals of [Zn(2)(Me(3)tacn)(2)(H(2)O)(4)(PhOPO(3))](ClO(4))(2).H(2)O (2), respectively. Blue crystals of [Cu(tacn)(2)](BNPP)(2) (3) formed in an aqueous solution of [Cu(tacn)Cl(2)], bis(p-nitrophenyl phosphate) (BNPP), and HEPES buffer (pH 7.4). Compound 1 crystallizes in the triclinic space group P1 (No. 2) with a = 9.8053(2) A, b = 12.9068(2) A, c = 22.1132(2) A, alpha = 98.636(1) degrees, beta = 99.546(1) degrees, gamma = 101.1733(8) degrees, and Z = 2 and exhibits trinuclear Cu(II) clusters in which square pyramidal metal centers are capped by two phosphate esters located above and below the plane of the metal centers. The trinuclear cluster is asymmetric having Cu...Cu distances of 4.14, 4.55, and 5.04 A. Compound 2 crystallizes in the monoclinic space group P2(1)/c (No. 14) with a = 13.6248(2) A, b = 11.6002(2) A, c = 25.9681(4) A, beta = 102.0072(9) degrees, and Z = 4 and contains a dinuclear Zn(II) complex formed by linking two units of [Zn(Me(3)tacn)(OH(2))(2)](2+) by a single phosphate ester. Compound 3 crystallizes in the monoclinic space group C2/c (No. 15) with a = 24.7105(5) A, b = 12.8627(3) A, c = 14.0079(3) A, beta = 106.600(1) degrees, and Z = 4 and consists of mononuclear [Cu(tacn)(2)](2+) cations whose charge is balanced by the BNPP(-) anions.

Coordination chemistry of copper(II) with oxaaza macrocyclic ligands. Crystal structure of a dinuclear tetramer copper(II) complex

A new series of copper(II) nitrate and perchlorate complexes with eight different oxaaza macrocyclic ligands (L 1–L 8) have been prepared and characterised. Complexes with the diiminic ligands L 1–L 6 have been obtained by template condensation of the appropriate dialdehyde and diamine precursors; the reduced L 7 and L 8 macrocycles have been synthesised using a direct route. The overall geometry and bonding mode have been deduced on the basis of elemental analysis data, IR, FAB, UV–Vis spectroscopy, cyclic voltammetry, and conductivity and magnetic susceptibility measurements. After treatment of an acetonitrile solution of the complex [L 6Cu](ClO 4) 2·5H 2O with acetic acid 15%, dark blue single crystals, the result of a secondary reaction, were isolated and characterised as a new binuclear tetramer copper(II) complex, with formula C 13H 28ClCu 2N 3O 10.

Synthesis and structural behavior of ternary copper(II) complexes containing reduced Schiff base N-(2-hydroxybenzyl)-4-aminobutyric acid and 1,10-phenanthroline

Ternary copper(II) complexes containing reduced Schiff base ligand N-(2-hydroxybenzyl)-4-aminobutyric acid (H 2Sab4) and 1,10-phenanthroline (phen) have been synthesized and characterized. Compound [Cu(Sab4)(phen)(H 2O)] · 5H 2O ( 1) was prepared from Cu(OAc) 2 · H 2O, H 2Sab4, phen, and LiOH in the ratio 1:1:1:2 in H 2O–MeOH. Green crystals of [Cu 3(Sab4) 2(phen)(H 2O) 2](ClO 4) 2 · 0.5H 2O ( 2) were isolated first from Cu(ClO 4) 2 · H 2O, H 2Sab4, phen, and LiOH in the ratio of 1:1:1:1. The filtrate furnished dark blue rhombohedral crystals of [Cu(H 2Sab4) 2(phen)](ClO 4) 2 ( 3), within a week. When the ratio of base was doubled, [Cu 2(Sab4)(phen) 3](ClO 4) 2 · 3H 2O ( 4) was the only product isolated. The crystal structures of 1, 3 and 4 have been determined. In the zwitterionic mononuclear complex 1 the Cu(II) has square pyramidal geometry with a water molecule at the apical position and the carboxylate anion hydrogen bonded to the lattice water molecules. Five highly ordered water molecules present in the lattices in 1 generate an interesting 3D hydrogen bond network in the solid state. In 3, the carboxylic acid is deprotonated by the secondary amino group of the ligand to form a zwitterion. The carbonyl O atoms and the protons of phenolic and –NH 2 + groups of the ligands are involved in extensive hydrogen bond network. The presence of intra and intermolecular π⋯π interactions between the two ligands is evident in 4.

Vibrational spectra and structure of the photochromic 2-(2′,4′-dinitrobenzyl)pyridine

The molecular structure of the pale yellow crystals of 2-(2′,4′-dinitrobenzyl)pyridine (CH 2 form) and its photo induced ‘enamine’ NH tautomer (dark blue crystals) have been studied by means of vibrational spectra and ab initio calculations. The Raman spectrum of the photo-sensitive CH 2 form was registered by NIR FT-Raman spectroscopy by means of the Nd:YAG laser as an excitation source. Ab initio calculations have been performed for the CH 2 and NH tautomers at the Hartree–Fock level using a 6-21G** basis set. The theoretical geometrical parameters for the isolated 2-(2′,4′-dinitrobenzyl)pyridine molecule (CH 2 form) are close to the literature X-ray diffraction data. According to the theory the dihedral angle between the benzene and pyridine ring planes in the NH photo induced tautomer is about 46°, the ortho-nitro group is twisted about 25° towards the benzene ring plane, whereas the para-nitro group is coplanar to the benzene ring. The assignment of the fundamental vibration frequencies of both 2-(2′,4′-dinitrobenzyl)pyridine tautomers CH 2 and NH have been performed on the basis of Raman and infrared spectra and ab initio force field calculations. The computed frequencies are in coincidence with the registered ones; the mean deviations are between 23.7 and 28.5 cm −1.

X-ray crystal structure of (eta(5)-pentaphenylcyclopentadienyl)[1-(eta(5/6)-phenyl)-2,3,4,5-tetraphenylcyclopentadienyl]iron(II), [Fe(eta(5)-C(5)Ph(5))[(eta(5/6)-C(6)H(5))C(5)Ph(4)]], a linkage isomer of decaphenylferrocene.

Very dark blue prismatic crystals of [Fe(eta(5)-C(5)Ph(5))[(eta(5/6)-C(6)H(5))(C(5)Ph(4))]], the linkage isomer of decaphenylferrocene, were grown from (3:1 v/v) hexane/ethyl acetate and characterized by single-crystal X-ray diffraction (space group P2(1)/n, R1(F) 0.0404). The iron atom is coordinated to two C(5)Ph(5) ligands: one with an eta(5)-C(5)-configuration and the other with a coordinated arene configuration. The phenyl groups of the (eta(5)-C(5)Ph(5)) ligand are oriented in a "paddle-wheel" arrangement about the C(5) ring, with which four of them make an average angle of approximately 53 degrees, the other, an angle of approximately 42 degrees. The coordinated C(6)H(5) ring of the other ligand is inclined at only approximately 5 degrees to the uncoordinated C(5) ring, with which three of the other four phenyl rings make an average angle of approximately 64 degrees, and the other (opposite the coordinated arene ring), an angle of 38 degrees.

The Influence of the Bulk Reduction State on the Surface Structure and Morphology of Rutile TiO2(110) Single Crystals

The authors have investigated the relationship between different types and amounts of bulk defects and the surface morphology of TiO{sub 2}(110) single crystals prepared by annealing in ultrahigh vacuum and in oxygen. Rutile TiO{sub 2}(110) specimens were cut from the same crystal and were heated in a furnace to different temperatures which resulted in different states of reduction (colors of the crystals). After characterization of the bulk defects with electron paramagnetic resonance (EPR), the specimens were studied with scanning tunneling microscopy (STM), low-energy He{sup +} ion scattering (LEIS), and work function measurements. EPR reveals that darker rutile crystals exhibit higher concentrations of extended Ti{sup 3+} related bulk defects such as crystallographic shear planes (CSP), with a decrease in substitutional and interstitial defects as compared to lighter crystals. Surface structures with (1 x 2) features are preferably formed upon UHV annealing on these darker crystals. LEIS measurements show that all of the crystals' (110) surfaces are reoxidized upon annealing in {sup 18}O{sub 2} (573 K, 1 x 10{sup {minus}6} mbar, 10 min) and that the {sup 18}O surface content is proportional to the bulk reduction state. UV-visible adsorption spectra and resistivity measurements also scale with the reduction states of crystals. Onlymore » the (1 x 1) structure is observed on the surface of slightly reduced crystals. Annealing in oxygen induces additional metastable structures, i.e., TiO{sub 2} clusters on blue crystals and rosette networks on dark blue crystals.« less

Synthesis and Crystal Structure of a Novel Dinuclear Copper(II) Complex, [Cu2(phen)2(H2O)2(OH)2](HCO3)2 · 6 H2O with phen = 1,10-phenanthroline

Dark blue plate-like crystals of [Cu2(phen)2 · (H2O)2(OH)2](HCO3)2 · 6 H2O were obtained from a CH3OH–H2O solution containing CuCl2, 1,10-phenanthroline (phen), sebacic acid and Na2CO3. The crystal structure (triclinic, P 1 (no. 2), a = 8.118(1), b = 9.624(1), c = 10.536(1) Å, α = 81.35(1)°, β = 88.51(1)°, γ = 75.77(1)°, Z = 1, R = 0.0332, wR2 = 0.0981 for 4163 observed reflections (F ≥ 2σ(F ) out of 4595 unique reflections) consists of divalent [Cu2(phen)2(H2O)2(OH)2]2+ complex cations, anionic (HCO3)22– dimers and H2O molecules. The divalent complex cations (d(Cu…Cu) = 2.905(1) Å) are centered at inversion centers. The Cu atoms are fivefold square-pyramidally coordinated by two nitrogen and three oxygen atoms from one bidentate chelating phen ligand, two bridging hydroxide groups and one axial water molecule (d(Cu–N)phen = 2.021(2), 2.024(2) Å; d(Cu–O)OH = 1.941(1), 1.949(1) Å; d(Cu–O)H2O = 2.254(2) Å). The divalent complex cations are stacked to form 2 D layers parallel (001) with 1 D π-π stacking interactions along [100] via the terminal phen rings. The dimeric (HCO3)22– anions and the hydrogen bonded H2O molecules are sandwiched between the 2 D layers.

Kristallstruktur des Oxo-Acetatkomplexes [Co7(μ4- O)2(O2CCH3)10(OPEt3)2] / Crystal Structure of the Oxo-Acetate Complex [Co7(μ4 -O)2(O2CCH3)10(OPEt3)2

Abstract Cobalt(II)acetate reacts with the silylated phosphinimine Me3SiNPEt3 at 230 °C to form a reaction mixture from which dark blue single crystals have been isolated by recrystallization from dichloromethane/ acetonitrile. They were identified by a crystal structure determination to be [Co7(μ4- O)2(O2CCH3)10(OPEt3)2] · 4 CH3CN (1). Lattice dimensions at 190 K: a = 1048.9(1), b = 1217.5(1), c = 1280.6(1) pm, a = 87.75(1)°, β = 77.72(1)°, y = 73.90(1)°, space group P1, Z = 1, R1 = 0.0257. 1 has a centrosymmetric cluster-like structure in which the central cobalt atom is connected via two μ4-oxygen atoms with the remaining six cobalt atoms to form a distorted Co(Co)6 octahedral skeleton. In addition, all cobalt atoms are linked by six ,μ2- O2CCH3 - groups and by four μ3-OC(O)CH3 - bridges

Titanium(II), -(III), and -(IV) Complexes Supported by Benzamidinate Ligands

The synthesis and reactivity of a wide range of titanium benzamidinates is described. Addition of 0.5 equiv of Me2Mg to the dichloride L2TiCl2 (L = PhC(NSiMe3)2) in Et2O yields the chloro−alkyl derivative L2Ti(Me)Cl in good yield. The addition of 2 equiv of PhCH2MgCl to the dichloride affords thermally sensitive L2Ti(CH2Ph)2 in moderate yield. Likewise, addition of 1 equiv of Me2Mg results in the clean formation of the dimethyl L2TiMe2. The dimethyl reacts with tert-butylamine in refluxing benzene to form the five-coordinate imido L2TiNCMe3, for which crystallographic data is presented. The imido reacts with acetone in C6D6 to form the bridging oxo derivative L2Ti(μ-O)2TiL[η1-NC(Ph)N(SiMe3)2]. Overnight reduction of the dichloride with 1% Na/Hg amalgam in tetrahydrofuran (THF) forms the Ti(III) derivative L2TiCl(THF), which is crystallized from hexanes in moderate yield. Carrying out the analogous reduction in toluene yields the base-free Ti(III) chloride, L2TiCl, for which crystallographic data is presented. Allowing the reaction (in toluene) to proceed for an additional 48 h results in further reduction and the formation of the end-on bound dinitrogen complex (L2Ti)2(μ-N2), which is isolated as dark blue crystals from hexanes in moderate yield. Reduction of L2Ti(Me)Cl with 1% Na/Hg amalgam in THF forms the Ti(III) methyl derivative which is isolated as the five-coordinate THF-free product L2TiMe upon evacuation and crystallization from hexamethyldisiloxane (HMDSO). The related Ti(III) alkyl L2TiCH2SiMe3 is readily prepared by reaction of LiCH2SiMe3 with L2TiCl in toluene. Carrying out the 1% Na/Hg amalgam reduction of the dichloride in the presence of CO results in the formation of the Ti(III) bridging-oxo species (L2Ti)2(μ-O), which is isolated in low yield. CO as the sole oxygen source is confirmed by the use of C18O, which yielded only labeled product. Analogous reduction in the presence of N,N,N‘,N‘-tetramethylethylenediamine (TMEDA) results in the C−N bond cleavage of an amidinate ligand and the cyclometalation of TMEDA. Two products, L2TiNSiMe3 and LTi[η2-Me3SiNC(H)Ph][η3-CH2N(Me)CH2CH2NMe2], are isolated in good yields by fractional crystallization from hexanes. The dinitrogen complex, (L2Ti)2(μ-N2), reacts with pyridine (Py) and 2,6-dimethylphenyl isocyanide (XylylNC) to form base adducts [L2Ti(Py)]2(μ-N2) and [L2Ti(CNXylyl)]2(μ-N2) without loss of the dinitrogen ligand. Crystallographic data for the Py adduct is presented. Oxidation reactions of (L2Ti)2(μ-N2) with a variety of oxygen and sulfur sources is reported. Reaction with dry O2 in the presence of pyridine gives the seven-coordinate peroxo complex L2Ti(η2-O2)Py. The related reaction with excess S8 yields the dark-green persulfido derivative L2Ti(η2-S2), for which crystallographic data is presented. The persulfido reacts overnight with Hg in toluene solution to give the bimetallic sulfido complex L2Ti(μ-S)2TiL[η1-NC(Ph)N(SiMe3)2], which is formed following a silyl-group migration. The analogous oxygen-containing product is best prepared by the reaction of powdered (L2Ti)(μ-N2) with dry O2. In the presence of excess pyridine, L2Ti(η2-S2) reacts with Hg to yield the terminal sulfido L2Ti(S)Py. The crystallographically characterized terminal-oxo derivative L2Ti(O)OPy is prepared by reaction of (L2Ti)(μ-N2) with an excess of pyridine N-oxide in toluene−pyridine.

A Novel Organolead(II) Species, the Plumbacycloalkane Derivative [CH2SiMe2C(SiMe3)2PbC(SiMe3)2SiMe2CH2

The title lead(II) derivative was obtained as dark blue crystals by treatment of PbCl2 with (TMEDA = N,N,N‘,N‘-tetramethylethylenediamine) in tetrahydrofuran and its structure determined by X-ray diffraction. The compound is in effect the first dialkylead(II) species to be structurally characterized. The C−Pb−C angle is 117.1(2)°. Analogous treatment of SnCl2 yielded a yellow solid, which was judged from spectroscopic data to be the TMEDA complex of the analogous stannacycloalkane.

Structure and Conductivity of an Electrocrystallized Ruthenium [1,8]Binaphthyridine Complex

AbstractFor the first time, the crystal structure of a RuII binaphthyridine complex and that of its corresponding oneelectron reduced product are reported. Reductive electrocrystallization of [Ru‐(binap‐2)3](PF6)2 (1, where binap‐2 = 3,3′‐dimethylene ‐2,2′ ‐ bi [1, 8] naphthyridine) from an acetonitrile solution resulted in the formation of dark blue crystals of the one‐electron reduction product, [Ru‐(binap‐2)3](PF6) (2) having one fewer PF−6 per formula unit. X‐ray analysis reveals that the reduced complex retains the three‐ligand d6 coordination around the central RuII. Based on electrostatic considerations and the positions of the PF−6 anions in the lattice, the added electron appears to be delocalized over two nearly equivalent binap‐2 ligands in 2, in marked contrast to monoreduced and electrocrystallized [Na ⊂ (trisbipyridyl cryptand)]0, in which the electron is localized on only one of the bipyridyl subunits. However, based on the available data, alternative interpretations are possible. The crystal packing diagram of 2 shows several intermolecular π–π interactions, with 12 of these being shorter than 3.5 Å. In contrast, there are no intermolecular distances shorter than 3.5 Å in the crystals of 1. Two‐probe electrical conductivity measurements under anaerobic conditions indicate that the crystals of 2 behave as semiconductors with a band gap of 0.53 eV, while those of the unreduced compound are insulating. This represents the first molecular semiconducting material with the potential for bidimensional behavior of its kind.

Keggin Cluster Formation by Hydrothermal Reaction of Tungsten Trioxide with Methyl Substituted Ammonium: The Crystal Structure of Two Novel Compounds, [NH2(CH3)2]6H2W12O40· ∼4H2O and [N(CH3)4]6H2W12O40· 2H2O

Tungsten(VI) oxides can be formed by mild hydrothermal reactions, with the exact crystalline structure being determined by the cations in solution. The impact on the reaction between tungstic acid and ammonium ions as the hydrogen atoms are systematically substituted by methyl groups is investigated. Ammonium and methylammonium (MA) cations form the pyrochlore structure type (NH4)xWO3+x/2·nH2O (A) and (MA)xWO3+x/2·nH2O (B). Ammonium may also form the hexagonal bronze tunnel structure. Using dimethylammonium (DMA), trimethylammonium (TrMA), and tetramethylammonium (TMA) leads to the formation of well crystallized Keggin structures: DMA6[H2W12O40] ·nH2O (C), DMA6[H2W12O40] · ∼4H2O (D), TrMA6[H2W12O40] (E), TrMA6[H2W12O40] · ∼2H2O (F), TMA6[H2W12O40] · 2H2O (G), and in some cases hexagonal tungsten bronzes. Characterization was done using powder and single crystal X-ray analysis, as well as IR and TGA methods. The pyrochlore structures have been refined by the Rietveld method. The powder patterns were indexed to the orthorhombic system (space groupPnma,a= 21.886(4),b= 21.469(4),c= 13.232(3) Å) forEand monoclinic system (P21/n,a= 19.273(4),b= 12.017(2),c= 12.253(2) Å, β = 90.70(1)°) in the case ofF. The crystal structures ofDandGwere determined by single crystal X-ray analysis. Blue crystals ofDare orthorhombic, space groupPnma,a= 22.446(3),b= 19.810(3),c= 12.854(2) Å,Vcell= 5716 Å3,Z= 4,dclc= 3.72 g/cm3(MoKα radiation, 2θmax.= 55°,R= 0.077 for 2076 reflections). Dark blue crystals ofGare orthorhombic, space groupPnma,a= 21.90(1),b= 21.507(7),c= 13.27(1) Å,Vcell= 6250 Å3,Z= 4,dclc= 3.54 g/cm3(MoKα radiation, 2θmax.= 55°,R= 0.052 for 4488 reflections). Both structures consist of a hexagonal close packed arrangement of the almost spherical Keggin anions [H2W12O40]−6. They are not isostructural because of a different orientation of the tungsten clusters.

THE SYNTHESIS OF A TRIS(1,4-BUTANEDIYLDITHIOETHYLENE-1,2-DITHIOLATE) COMPLEX OF VANADIUM. STRUCTURE AND ELECTRONIC PROPERTIES

Abstract A monoanionic vanadium complex has been isolated from the reaction of vanadium(III) chloride and the dipotassium salt of the dithiolene, 1,4-butanediyldithioethylene-1,2-dithiolate (BDDT). The complex, isolated as the tetraethylammonium salt and recrystallized from acetone, produced dark blue crystals suitable for an X-ray structural study. The material crystallizes in the monoclinic system, space group P21/c, with a = 10.798(11) A, b = 19.244(30) A, c = 36.370(42) A, β = 92.23(7)°, V = 7552(12) A3, z = 8, and R = 0.1106. Extended Huckel molecular orbital calculations suggest that this is best described as a V(V) complex. In contrast, however, a comparison of the MO calculation with the tris-vanadium complex of 1,2-ethanediyldithioethylene-1,2-dithiolate (DDDT) suggests this latter system is more appropriately described as a lower oxidation state of vanadium with a partially oxidized ligand. The structural data also suggest this interpretation.

Eine zweite polymorphe Form von Te4(WCl6)2 / A Second Polymorphie Form of Te4(WCl6)2

The reaction of tellurium with WCl6 in the presence of bromine in a sealed evacuated ampoule in the temperature range from 220 to 150 °C yields dark blue monoclinic crystals of β-Te4(WCl6)2, space group P21/c, lattice constants a = 664,3(2), b = 1273,2(3), c = 1233,6(3) pm, ß - 94,13(3)°. The structure is built of square planar Te4 2+ cations and slightly distorted octahedral WCl6 - anions and shows a close relationship to the previously reported triclinic α-form, which was obtained in the absence of bromine. The difference between the two structures lies in a different packing of the ions

Zur Kenntnis eines gemischtvalenten Lanthanoxovanadats: La11V4+V35+O26

Single crystals of La11V4+V35+O26 were prepared by high temperature reactions in an N2/H2 mixture above the melting point of the initial oxides V2O5–La2O3. X-ray investigations of the dark blue crystals reveal triclinic symmetry, space group Ci1(P1̄) with α = 7.088 Å, β = 10.213 Å, χ = 10.250 Å, α = 89.59°, β = 71.10°, τ = 70.00°, Z = 1. The lanthanum-rich compound exhibits a new structure type characterized by a complicated La11O2619- network with incorporated V4+V5+ ions. The VO4 tetrahedra are isolated from each other and occupied with V4+ and V5+ in a statistical manner.

Mobile Metal-Metal Bonds: Studies on Mixed Valence Ir3 and Ir4 Clusters

The dicationic clusters ((CsMes)41r4S4)2+ ( (112+) and ((C5Me5)31r3S~)2+ were prepared by treatment of ( (C5Me~)IrCl2)2 with (Me3Si)zS followed by ion exchange chromatography. Crystallographic characterization of the tetrairidium cluster ( 112+ reveals a cubane motif consisting of interpenetrated Ir4 and S4 tetrahedra. The Ir4 core is distorted from idealized tetrahedral symmetry by virtue of a single IrIv-1rIv bonding contact of 2.764(1) A. The four IrIv-Irlll contacts are nearly equivalent at 3.5 A, while the Irlll...Irlll distance is 3.683( 1) A. Variable-temperature 1H NMR studies indicate that (112+ is fluxional with a coalescence temperature of 13 OC (400 MHz), corresponding to AG* = 57 kJ/mol. This dynamic process is attributed to migration of the metal-metal bond arising from internal Ir*v/IrIII self-exchange. Cyclic voltammetry studies of ( 112+ reveal a pair of reversible one-electron reductions at -21 8 and -487 mV vs Ag/AgCl. Chemical reduction of (1)2+ was effected with cobaltocene while the neutral cluster could be reoxidized with HC1/02. In the solid state (2)2+ features a trigonal-bipyramidal Ir3S2 core with average Ir-Ir contacts of 2.82 8, and Ira distances of 2.28 A. Cyclic voltammetry studies indicate that this closo dication undergoes two single electron reductions at -712 and -993 mV. Cobaltocene reduction of (2)2+ afforded dark blue crystals of neutral (21°. Variable-temperature lH NMR spectra of (21° reveal dynamic behavior, with coalescence at 60 OC (400 MHz), corresponding to AG* = 64 kJ/mol. These structural dynamics suggest migration of the nonbonding Ir-Ir interaction among the three edges of the Ir3 triangle.