A new (3,4,7)-connected topology framework based on [Cd2(CO2)3O4N2] second building unit

A new 3D coordination polymer [Cd₂(L³)(BTC)(H₂O)] (1) (HL³ = 3,5-bis(pyridin-3-ylmethoxy)benzoic acid, H₃BTC = 1,3,5-benzenetricarboxylic acid), has been isolated under hydrothermal condition and characterized by single-crystal X-ray diffraction. Compound 1 is constructed from Cd₂-based second building units (SBUs) [Cd₂(CO₂)₃O₄N₂] and displays a 3D (3,4,7)-connected net with (4²·6)(4³·6³)(4⁵·6¹¹·8⁵) topology. In addition, the photoluminescent spectra indicate compound 1 may be a good candidate for blue-luminescent materials.     

Structure and magnetic properties of a novel branch-like one-dimensional cyano-bridged assembly [Cu(L)]3[Fe(CN)6]2·8H2O (L = 6,13-dimethyl-6-nitro-1,4,8,11-tetraazabicyclo[11.1.1]pentadecane)

The one-dimensional coordination polymer like fern branch, [Cu^II(L)]₃[Fe^III(CN)₆]₂·8H₂O (1), which is linked by azamacrocyclic copper(II) complex and iron(III) hexacyanide, has been synthesized and characterized by single crystal X-ray crystallography and magnetic susceptibility measurement (L = 6,13-dimethyl-6-nitro-1,4,8,11-tetraazabicyclo[11.1.1]pentadecane). Compound 1 shows a weak ferromagnetic coupling between the copper(II) and low spin iron(III) ions in the one-dimensional chain structure.     

Two-equivalent electrochemical reduction of a cyano-complex [Tl(CN)2] and the novel di-nuclear compound [(CN)5Pt−Tl]

Extending our recent insights in two-electron transfer microscopic mechanisms for a Tl^III/Tl^I redox system [D.E. Khoshtariya, et al., Inorg. Chem. 41 (2002) 1728], the electrochemical response of glassy carbon electrode in acidified solutions of Tl^III (ClO₄)₃ containing different concentrations of sodium cyanide has been extensively studied for the first time by use of cyclic voltammetry and the CVSIM curve simulation PC program. The complex [Tl^III(CN)₂]⁺ has been thoroughly identified electrochemically and shown to display a single well-defined reduction wave (which has no anodic counterpart), ascribed to the two-equivalent process yielding [Tl^I(aq)]⁺. This behavior is similar to that of [Tl^III(aq)]³⁺ ion in the absence of sodium cyanide, disclosed in the previous work, and is compatible with the quasi-simultaneous yet sequential two-electron transfer pattern (with two reduction waves merged in one), implying the rate-determining first electron transfer step (resulting in the formation of a covalently interacting di-thallium complex as a metastable intermediate), and the fast second electron transfer step. Some preliminary studies of the two-equivalent reduction of directly metal-metal bonded stable compound [(CN)₅Pt^II-Tl^III]⁰ has been also performed displaying two reduction waves compatible with a true sequential pattern.     

Electrochemical behavior and its electrocatalytic properties of chemically modified electrode with Keggin-type [SiNi(H2O)W11O39]

A monolayer of Keggin-type heteropolyanion [SiNi(H₂O)W₁₁O₃₉]⁶⁻ was fabricated by electrodepositing [SiNi(H₂O)W₁₁O₃₉]⁶⁻ on cysteamine modified gold electrode. The monolayer of [SiNi(H₂O)W₁₁O₃₉]⁶⁻ modified gold electrode was characterized by atomic force microscopy (AFM) and electrochemical method. AFM results showed the [SiNi(H₂O)W₁₁O₃₉]⁶⁻ uniformly deposited on the electrode surface and formed a porous monolayer. Cyclic voltammetry exhibited one oxidation peak and two reduction peaks in 1.0 M H₂SO₄ in the potential range of −0.2 to 0.7 V. The constructed electrode could exist in a large pH (0-7.6) range and showed good catalytic activity towards the reduction of bromate anion (BrO₃⁻) and nitrite (NO₂⁻), and oxidation of ascorbic acid (AA) in acidic solution. The well catalytic active of the electrode was ascribed to the porous structure of the [SiNi(H₂O)W₁₁O₃₉]6⁻ monolayer.     

Diplatinum(III) [Cl2(μ2-amidinate)4] compound derived from air oxidation of mononuclear cis-[Pt(NH3)2(amidine-κ)2] complex

The dinuclear platinum(III) complex [Pt₂Cl₂{μ₂-N(H)C(Et)N(H)}₄] (2) has been prepared by heating cis-[Pt(NH₃)₂{NHC(NH₂)Et}₂](Cl)₂ (cis-1) under aeration conditions in an EtOH/H₂O mixture at 70 °C for 2 d and it was characterized by elemental analyses (C, H, N), ESI⁺-MS, IR, ¹H and ¹³C NMR spectroscopies and also by X-ray diffraction. Complex 2 represents the second Pt^III dimer stabilized by the amidinate ligand ever known and it has a lantern-type structure with four amidinate ligands bridging two Pt^III centers with Pt–Pt distance of 2.4809(2) Å.     

Crystal structure of Kuzel's salt 3CaO·Al2O3·1/2CaSO4·1/2CaCl2·11H2O determined by synchrotron powder diffraction

The crystal structure of Kuzel's salt has been successfully determined by synchrotron powder diffraction. It crystallizes in the rhombohedral R3? symmetry with a = 5.7508 (2) Å, c = 50.418 (3) Å, V = 1444.04 (11) ų. Joint Rietveld refinement was realized using three X-ray powder patterns recorded with a unique wavelength and three different sample-to-detector distances. Kuzel's salt is the chloro-sulfoaluminate AFm phase and belongs to the layered double hydroxide (LDH) large family. Its structure is composed of positively charged main layer [Ca₂Al(OH)₆]⁺ and negatively charged interlayer [Cl_0.50·(SO₄)_0.25·2.5H₂O]⁻. Chloride and sulfate anions are ordered into two independent crystallographic sites and fill successive interlayer leading to the formation of a second-stage compound. The two kinds of interlayer have the compositions [Cl·2H₂O]⁻ and [(SO₄)_0.5·3H₂O]⁻. The crystal structure explains why chloride and sulfate anions are not substituted and why the formation of extended solid solution in the chloro-sulfate AFm system does not occur.     

Synthesis, crystal structure and magnetic properties of a new three-dimensional porous framework: [Gd2(BDA)3(DMF)2(H2O)4] · 2DMF

The open framework compound of [Gd₂(BDA)₃(DMF)₂(H₂O)₄] · 2DMF (1), prepared by heating GdCl₃ with 2,2′-bipyridyl-4,4′-dicarboxylatic acid (BDA) in mixed solvent, is constructed from BDA linking up polymeric [GdO₅(DMF)(H₂O)₂]_n tethers. The 1D channels are filled with coordinated and uncoordinated DMF molecules hydrogen bonding to terminal aqua ligands. The study of the temperature dependent magnetic susceptibilities revealed that there are ferromagnetic interactions between intra-chain Gd^III atoms and weak antiferromagnetic interactions between inter-chain Gd^III atoms.     

Co-polymerization of propylene oxide and CO2 using early transition metal (groups IV and V) metallocalix[n]arenes (n = 4, 6, 8)

A number of metallocalix[n]arenes, where n = 4, 6, or 8, of titanium and vanadium have been screened for their ability to act as catalysts for the co-polymerization of propylene oxide and CO₂ to form cyclic/polycarbonates. The vanadium-containing catalysts, namely [VO(L¹Me)] (1), [(VO₂)L²H₆] (2), [Na(NCMe)₆]₂[(Na[VO]₄L²)(Na(NCMe))₃]₂ (3), [VO(μ-OH)L^3/H₂]₂∙6CH₂Cl₂ (4), {[VO]₂(μ-O)L⁴[Na(NCMe)₂]₂} (5), {[V(Np-tolyl)]₂L⁴} (6) and [V(Np-RC₆H₄)Cl₃] (R = Cl (7), OMe (8), CF₃ (9)), where L¹H₃ = methylether-p-tert-butylcalix[4]areneH₃, L²H₈ = p-tert-butylcalix[8]areneH₈, L³H₄ = p-tert-butylthiacalix[4]areneH₄, L⁴H₆ = p-tert-butyltetrahomodioxacalix[6]areneH₆, performed poorly, affording, in the majority of cases, TONs less than 1 at 90°C over 6 h and low molecular weight oligomeric products (M_n ≤ 1665). In the case of the titanocalix[8]arenes, {(TiX)₂[TiX(NCMe)]₂(μ₃-O)₂(L²)} (X = Cl (10), Br (11), I (12)), which all adopt a similar, ladder-type structure, the activity under the same conditions is somewhat higher (TONs >6) and follows the trend Cl > Br > I; by comparison the non-calixarene species [TiCl₄(THF)₂] was virtually inactive. In the case of 10, it was observed that the use of PPNCl (bis[triphenylphosphine]iminium chloride) as co-catalyst significantly improved both the polymer yield and molecular weight (M_n 3515). The molecular structures of the complexes [HNEt₃]₂[VO(μ-O)L³H₂]₂∙3CH₂Cl₂ (4∙3CH₂Cl₂), [VO(μ-OH)L^3/H₂]₂∙6CH₂Cl₂ (4^/) (where L^3/H₂ is a partially oxidized form of L³H₄) and {(TiCl)₂[TiCl(NCMe)]₂(μ₃-O)₂(L²)}·6.5MeCN (10·6.5MeCN) are reported.     

A novel polyoxometalate-based metal-organic compound constructed from an unprecedented [Ag8(Hpyttz)4(H2pyttz)2] cluster and an in-situ [VW12O40]3 − anion

A novel polyoxometalate (POM)-based metal-organic compound constructed from a multinuclear Ag^I cluster and Keggin-type [VW₁₂O₄₀]^3 − anion, [Ag₄(Hpyttz)₂(H₂pyttz)][HVW₁₂O₄₀]·3H₂O (1) (H₂pyttz = 5′-(pyridin-4-yl)-1H,2′H-3,3′-bi(1,2,4-triazole), was hydrothermally synthesized and characterized by IR spectroscopy, TG analysis, powder and single-crystal X-ray diffraction. In compound 1, [VW₁₂O₄₀]^3 − (VW₁₂) was in-situ transformed from [SiW₁₂O₄₀]^4 − anion. Eight Ag^I ions were connected by six Hpyttz/H₂pyttz ligands with three coordination modes forming an unprecedented [Ag₈(Hpyttz)₄(H₂pyttz)₂] cluster, which connected with six VW₁₂ anions to construct a 2-D double-layer (3,6)-connected network with {4³}₂{4⁶.6⁶.8³} topology. Moreover, the photocatalytic activity of 1 has been investigated.     

Gold(I) phosphine complexes with bis(2-pyridyl)diselenoether: Synthesis and structure elucidation

Bis(2-pyridyl)diselenoether with the general formula (2-PySe)₂(CH₂) (L) reacts with Ph₃PAuCl and [(dpph)(AuCl)₂] dpph = 1,6-bis(diphenylphosphino)hexane to produce the respective complexes [(L)Au₂(PPh₃)₂](PF₆)₂ (1) and [(L)(dpph)Au₂(PF₆)₂]_n (2). These complexes were isolated in crystalline form and studied using spectroscopic and X-ray diffraction techniques. The coordination of the ligand (2-PySe)₂(CH₂) (L) to the gold(I) metal centers in complexes [(L)Au₂(PPh₃)₂](PF₆)₂ (1) and [(L)(dpph)Au₂(PF₆)₂]_n (2) occurs via the nitrogen atom of the pyridine ring, with no interaction with the selenium atoms of the bis(2-pyridyl)diselenoether. The gold derivative (Ph₃PAuCl or [(dpph)(AuCl)₂]) is responsible for the formation of a molecular complex (1) or a polymeric complex (2), and in both compounds the gold(I) metal atoms adopt an almost linear geometry.     

A novel (3,4,8)-connected 3D topology framework based on [Gd2(bpdc)3(H2O)3] second building units

A new 3D coordination polymer {[Gd₂(bpdc)₃(H₂O)₃]·H₂O}_n(1) has been isolated from the reaction of 2,2′-bipyridine-4,4′-dicarboxylic acid (H₂bpdc) and Gd(III) salts under hydrothermal conditions. Single-crystal X-ray diffraction study shows that compound 1 is constructed from Gd₂-based second building units (SBUs) [Gd₂(bpdc)₃(H₂O)₃] and displays a 3D (3,4,8)-connected net with (4²·6)(3²·4²·5²)(3²·4⁵·5⁴·6¹¹·7⁶) topology. A thermogravimetric analysis of 1 shows a high thermal stability. The magnetic behavior of 1 reveals a weak antiferromagnetic interaction between Gd(III) ions.     

[(μ-Fluoro) bis{(triphenyl) (p-tolyl) antimony}] iodide

The crystal structure of the mixed halide compound, [Ph₃(p-tolyl)Sb]F_0.5I_0.5 (4), obtained from [Ph₃(p-tolyl)Sb] [BF₄] and NaI, has been determined. Compound 4 is an ionic compound with a novel fluoride bridged cation, [Ph₃(p-tolyl)SbFSb (p-tolyl)Ph₃]⁺, and an independent I⁻ anion. The geometry of the Sb centres in the centrosymmetric cation is distorted trigonal bipyramidal with the axial sites occupied by a phenyl group [SbC(7) = 2.127(8) Å] and the bridging fluoride [SbF = 2.2856 (11) Å]; the C(7)-SbF angle is 177.6(2) °. The average SbC(equatorial) bond length of 2.099 Å is only slightly less than the SbC(axial) bond length.     

Variations in the crystalline deposits formed upon electrochemical oxidation of the anions, [Ir(CO)2X2] (X = Cl, Br, and I)

The electrochemical properties of the ions [Ir(CO)₂X₂]⁻ (X = Cl, Br, and I) have been studied in dichloromethane solutions using cyclic voltammetry, chronoamperometry, electrochemical quartz crystal microbalance (EQCM), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and infrared spectroscopy. For the chloro and bromo salts, the anion [Ir(CO)₂X₂]⁻ is oxidized initially to form [Ir(CO)₂X₂]⁺. The standard rate constants for the two-electron oxidations of [Ir(CO)₂X₂]⁻ are 7.8(±0.6) × 10⁻³ and 9.2(±0.9) × 10⁻⁴ cm s⁻¹ for the redox couples, [Ir(CO)₂Cl₂]^−/+ and [Ir(CO)₂Br₂]^−/+, respectively. The processes following electrolysis lead to the formation of two types of crystalline deposits on the electrode surface: needles and plates. The relative amounts of these solid phases that form depend mainly on the concentration of iridium complex in solution and on the time window of experiment. The strong intermetallic Ir-Ir interaction is responsible for the formation of the one-dimensional iridium complex chain. The crystal structures of the needle phases formed from [Ir(CO)₂Cl₂]⁻ and [Ir(CO)₂Br₂]⁻ are the same and belong to the space group Cmcm (no. 63). The stoichiometry of the one-dimensional crystals depends on the constitution of the supporting electrolyte: (TAA)_0.6[Ir(CO)₂Cl₂] and (TAA)_0.7[Ir(CO)₂Br₂] (TAA is tetra(alkyl)ammonium cation) salts are formed on the electrode surface. The formation of large three-dimensional crystal is responsible for the accumulation of electroactive materials on the electrode surface. The irreversible oxidation of [Ir(CO)₂I₂]⁻ leads only to the formation of large, plate-like crystals on the electrode surface, no needles are formed.     

An intertwined double chain constructed by [SiMo12O40] clusters and unusual [Cu2(DF)2H2O] dimers

A new compound, {[Cu₂(DF)₂H₂O]₂SiMo₁₂O₄₀} (1) (DF = 4,5-diazafluoren-9-one), has been hydrothermally synthesized and characterized by routine methods and single crystal X-ray diffraction. In 1, all the DF only adopt the unusual bidentate coordination mode for the first time coordinating to Cu atoms to form copper-dimers which link [SiMo₁₂O₄₀]⁴⁻ clusters obtaining an intertwined double chain. Furthermore, the luminescent and electrochemical properties of the title compound have been studied.     

Synthesis and structure of [{As(NBu)3}2Li6] containing an [As(NBu)3] trianion

Attempts to prepare the [As(N^tBu)₃]³⁻ trianion by the reaction of As(NMe₂)₃ with [^tBuNHLi]_n (1:3 monomer equiv.) proved unsuccessful. However, if the reaction is carried out with an excess of ^tBuNH₂ (3 equiv.) the target complex [{As(N^tBu)₃}₂Li₆] (1) is obtained. This is the first example of a complex containing an [As(NR)₃]³⁻ trianion.     

Synthesis, structure and photoluminescence of a novel palladium(I) compound: [Pd3(μ3-Cl)2(dppp)3][Pd2(μ2-Cl)3(PPh3)2](PPh3)2

Pd(PPh₃)₂Cl₂ reacts with PdCl₂ and 1,3-bis(diphenylphosphine)propane (dppp) in ethanol–DMF–pyridine mixed solvent to yield a novel palladium(I) compound [Pd₃(μ₃-Cl)₂(dppp)₃][Pd₂(μ₂-Cl)₃(PPh₃)₂](PPh₃)₂. It features an isolated structure based on [Pd₃(μ₃-Cl)₂(dppp)₃]⁺ cations having triangulo-palladium clusters and [Pd₂(μ₂-Cl)₃(PPh₃)₂]⁻ anions in which the coordination environment of palladium is an unusual tetrahedral geometry. Its photoluminescence is measured.     

Electrocatalyst materials for fuel cells based on the polyoxometalates—K7 or H7[(P2W17O61)Fe(H2O)] and Na12 or H12[(P2W15O56)2Fe4(H2O)2]

Free acids of the iron substituted heteropoly acids (HPA), H₇[(P₂W₁₇O₆₁)Fe^III(H₂O)] (HFe1) and H₁₈[(P₂W₁₅O₅₆)₂Fe^III₂(H₂O)₂] (HFe2) were prepared from the salts K₇[(P₂W₁₇O₆₁)Fe^III(H₂O)] (KFe1) and Na₁₂[(P₂W₁₅O₅₆)₂Fe^III₄(H₂O)₂] (NaFe4), respectively. The iron-substituted HPA were adsorbed on to XC-72 carbon based GDLs to form HPA doped GDEs after water washing with HPA loadings of ca. 1 μmol. The HPA was detected throughout the GDL by EDX. Solution electrochemistry of the free acids are reported for the first time in sulfate buffer, pH 1-3. The hydrogen oxidation reaction was catalyzed by KFe1 at 0.33 V, with an exchange current density of 38 mA/cm². Moderate activity for the oxygen reduction reaction was observed for the iron substituted HPA, which was dramatically improved by selectively removing oxygen atoms from the HPA by cycling the fuel cell cathode under N₂ followed by reoxidation to give a restructured oxide catalyst. The nanostructured oxide achieved an OCV of 0.7 V with a Tafel slope of 115 mV/decade. Cycling the same catalysts in oxygen resulted in an improved catalyst/ionomer/carbon configuration with a slightly higher Tafel slope, 128 mV/decade but a respectable current density of 100 mA/cm² at 0.2 V.     

Water-soluble Pt3S2 cluster with phosphine ligands

Reaction of [Pt(P(CH₂OH)₃)₂Cl₂] with H₂S in methanol produces new water-soluble trinuclear complex [Pt₃(μ₃-S)₂(P(CH₂OH)₃)₆]Cl₂ (1). It was characterized by IR-spectroscopy, ³¹P NMR, X-ray structure analysis, mass-spectra and cyclic voltammetry.     

Nickel complexes bearing 2-(1H-benzo[d]imidazol-2-yl)-N-benzylidenequinolin-8-amines: Synthesis,structure and catalytic ethylene oligomerization

A series of 2-(1H-benzo[d]imidazol-2-yl)-N-benzylidenequinolin-8-amines was synthesized and characterized. They are stable as solids while displaying a tendency to decompose in solution. On reaction with NiCl₂, different coordination pattern sets of L·NiCl₂ or [L₂Ni]²⁺·2Cl⁻ are obtainable in THF or ethanol. When activated by Et₂AlCl, the complexes L·NiCl₂ exhibit good to high catalytic activities and selectivities for 1-C₄ in ethylene oligomerization, while the complexes [L2Ni]²⁺·2Cl⁻ hardly showed any activity, which is attributable to nickel coordination by two ligands barring interaction of ethylene with the metal center.     

Binuclear cyano-bridged complex derived from [MnIII(salpn)] and [FeIII(CN)6]: Synthesis,structure and magnetic properties

The reaction of the neutral [Mn(salpn)C(CN)₃(H₂O)] (salpn^2 − = N,N^′-1,3-propylenebis(salicylideneiminato) dianion) with [Fe^III(CN)₆]^3 − in the presence of strong oxidizer (NH₄)₂S₂O₈ yields a binuclear anion complex [NH₃CH₂CH₂CH₂NH₃]^2 +{[Mn^III(salpn)(H₂O)][Fe^III(CN)₆]}^2 − (1). Its structure, DC and AC susceptibility have been studied. Frequency dependence of the AC susceptibility characteristic for single-molecule magnets has been found.