Stable Solids Research Articles

Synthesis and redox behavior of ruthenocene-terminated oligoenes: characteristic and stable two-electron redox system and lower potential shift of the two-electron oxidation wave with elongating conjugation.

Ruthenocene-terminated butadienes and hexatrienes were prepared by the Wittig reaction of 3-ruthenocenyl-2-propenals with ruthenocenylmethylphosphonium salts and the Mukaiyama coupling of the propenals, respectively. Cyclic voltammetry of these complexes indicated that they were involved in a stable two-electron redox process. The oxidation potentials for ruthenocene-terminated oligoenes shifted progressively to lower potential with the increasing CH==CH units as follows: Rc--Rc (0.32 V)>RcCH==CHRc (+0.09 V)>Rc(CH==CH)(2)Rc (-0.06 V)>Rc(CH==CH)(3)Rc (-0.07 V), (Rc=ruthenocene). The tendency is in remarkable contrast to that in the successive one-electron redox process. These complexes were chemically oxidized to give stable crystalline solids, whose structures were confirmed by NMR spectroscopy and X-ray analysis to be oligoene analogues of a bis(fulvene) complex, for example, [(eta(5)-C(5)Me(5))Ru[mu(2)-eta(6):eta(6)-C(5)H(4)CH(CH==CH)(n)CHC(5)H(4)]Ru(eta(5)-C(5)Me(5))](2+) (n=1 or 2). The DFT calculation of the two-electron-oxidized species reproduced well the fulvene-complex structure for the ruthenocene moieties. Since both the neutral and oxidized species are stable and chemically reversible, this redox system may be serviceable as a two-electron version of the ferrocene one-electron redox system.

X-ray and 13C CP MAS investigations of structure of two genistein derivatives

Structural and spectroscopic properties of two distinctly different derivatives of genistein ( 1), ionic and covalent, engaging the most acidic of its three phenolic functions, have been investigated. Both the 7-O-silyl ether ( 2), and ammonium salt ( 3), are stable solids, considered to be useful intermediates for achieving further chemical transformations in a manner securing highly regioselective outcome. It turned out that these two molecules contain genistein structural fragment involved in many intra- and intermolecular hydrogen bonds. In the case of 2, some infinite chains of coupled intra- and intermolecular hydrogen bonds are formed supported by hydrogen bonding to water molecules. In the structure of 3, a helical arrangement of genistein moieties is formed with the cations kept in voids. Single crystal X-ray diffraction shows that the aromatic ring B in both structures is rotated with respect to the AC fused rings of the chromenone moiety by ca. 36° ( 2) and 50° ( 3). Both new compounds crystallise as monohydrates. The number of peaks observed in the solid-state 13C spectra of 2 and 3 corresponds to the number of magnetically non-equivalent carbons and it is in satisfactory agreement with the X-ray crystal structures of both genistein derivatives.

Supramolecular Metal—Organometallic Coordination Networks Based on Quinonoid π‐Complexes

AbstractFor Abstract see ChemInform Abstract in Full Text.

Homogeneous oxidative coupling catalysts: stoichiometry and characterization of the first stable oxotetranuclear solids [(Pip) nCuX] 4O 2 ( n=1 or 2, Pip=piperidine, X=Cl, Br, I)

Copper(I) halides react quantitatively with piperidine (Pip) in dioxygen-free methylene chloride or nitrobenzene to form tetranuclear copper(I) complexes [(Pip) n CuX] 4; n=1 or 2, X=Cl, Br or I. These complexes are very soluble and completely reduce dioxygen to dioxo bridging ligand, with stoichiometry, Δ[Cu(I)]/Δ[O 2]=4.0. The stable oxo solids [(Pip) n CuX] 4O 2 mimic tyrosinase copper protein. They act as a homogeneous oxidative coupling catalysts for phenols. Electronic transition spectra in the near infrared with high molecular absorptivity are diagnostic for tetranuclear “Cu 4X 4” core structure. The electronic transitions are more likely due to charge transfer between a minimum of three halo ligands and copper(II) center. The room temperature EPR spectra of [(Pip) n CuX] 4O 2 in methylene chloride are isotropic with four hyperfine lines. The room temperature solid-state EPR spectra of [PipCuX] 4O 2 show an axial spectra with d x 2− y 2 ground state, suggesting square pyramidal arrangement of the five coordinated ligands around copper(II) centers. Cyclic voltammetry measurements show that they are more likely irreversible in character and show slight quasi-reversability when X=Br or I. Constant potential electrolysis indicate that the number of electrons consumed are equal to four electrons which will be due to the reduction of four copper(II) to copper(I).

Unsuccessful/successful attempts to produce penta(heteroaryl)-phosphoranes/-arsoranes R5E (E = P, As; R = 2-furyl, 2-thienyl).

Tri(2-thienyl)phosphine (1) has been transformed into chlorotri(2-thienyl)phosphonium chloride (3) in the reaction with hexachloroethane, into tetra(2-thienyl)phosphonium bromide (4) in a NiBr2-catalyzed quaternization with 2-bromothiophene, and into the p-tolylsulfonyliminotri(2-thienyl)phosphorane (6) using "chloramine T". Attempts to generate the homoleptic penta(2-thienyl)phosphorane (2-C4H3S)5P (5) by treating 3, 4, 6 or the known (PhO)3P=NSO2C6H4-2-Me (9) with 2-thienyllithium were unsuccessful. Tri(2-furyl)phosphine (2) was converted into the related imine 7, but the reaction of 7 or of 9 with 2-furyllithium failed to give (2-C4H3O)5P (8). It was only with the strained phosphorane Ph(C12H8)P=NSO2C6H4-4-Me (C12H8= 2,2'-biphenylylene) (10) that with 2-C4H3OLi the corresponding phosphorane Ph(C12H8)P(C4H3O-2)2 (11) could be obtained (31P NMR: delta-106.7 ppm). In the arsenic series, tri(2-thienyl)- and tri(2-furyl)arsine (12, 13) were converted into the tosylimino compounds (14, 15) and successfully transformed into the homoleptic arsoranes with 2-C4H3E-Li: penta(2-thienyl)- (16) and penta(2-furyl)-arsorane (17) are stable colourless crystalline solids, the NMR spectra of which indicate rapid pseudo-rotation in solution. The single crystal structure analysis of 17 shows an only slightly distorted trigonal-bipyramidal configuration. In crystals of the phosphine 2 and the arsine 13 the molecules have a propeller configuration with approximate C3v symmetry for the former, but Cs symmetry for the latter. The crystal structures of the precursors or intermediates 3, 4, 6, 9, and 10 have also been determined.

Pyrimidin‐/Thiazol‐/Thiazolin‐ylidenamidothiophosphoric Dichlorides.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Refractive Index Changes of Amorphous Diarylethenes Containing 2,4-Diphenylphenyl Substituents

Photochromic diarylethene derivatives containing 2,4-diphenylphenyl substituents formed stable amorphous solids and showed reversible solid-state photochromism. Refractive indices of the amorphous films changed reversibly with the photochromic reactions as much as Δn = 0.028 at 817 nm. Changes in both absorption band and static polarizability contributed to the large refractive index modulation.

Supramolecular metal-organometallic coordination networks based on quinonoid pi-complexes.

The use of organometallic pi-complexes in the coordination-directed self-assembly of polymeric structures is a new area with many potential applications. Supramolecular metal-organometallic coordination networks (MOMNs), which are described herein, consist of metal ion or metal cluster nodes connected by bifunctional "organometalloligands" that serve as spacers. The organometalloligand utilized in this work is the stable anionic complex (eta(4)-benzoquinone)Mn(CO)(3)(-) (p-QMTC), which binds through both quinone oxygen atoms to generate MOMNs having both backbone and pendant metal sites. In many cases the MOMNs are obtained as neutral and thermally stable solids, with molecular structures that depend on the geometrical and electronic requirements of the metal nodes, the solvent, and the presence of organic spacers. Redox-active quinone-based organometallic pi-complexes permit the construction of an impressive range of coordination network architectures and hold much promise for the development of functional materials.

Synthesis and structure of novel, air-stable carbyne complexes of tungsten

New Fischer type carbyne complexes of tungsten, L(CO) 2WCR/Ar, 1b– 7b, where R=CH 3, Ar=substituted phenyl, and LH=(2-hydroxyphenyl)-bis(3,5-dimethylpyrazolyl)methane, with L − being a tridentate, uninegative ligand, were synthesized from W(CO) 6 via tetraethylammonium acylmetallate salt, as thermally stable and air-stable solids. In another complex, 8b, the aryl ring is complexed with tricarbonylchromium. Crystal structure of a representative complex was determined to confirm structural assignment.

Formation, Characterization, and Stability of Novel Aluminocarbosilazane Macromolecules

A novel class of polycarbosilazaneċAlCl3 macromolecules (AlCSZ) with a Si/Al molar ratio of 1 : 1, 2 : 1, and 3 : 1 were prepared by a two‐step reaction, formation of H2NCH2CH2NH2ċAlCl3 adducts followed by condensation of H2NCH2CH2NH2 with (CH3)2SiCl2 in an aprotic solvent containing triethylamine base. The resulting AlCSZ materials were examined by elemental analysis, infrared spectroscopy (FT‐IR), mass spectrometry (MS), and powder x‐ray diffraction (XRD). The average polycarbosilazane chain–chain distances in the aluminum‐free polycarbosilazane and these AlCSZ macromolecules were estimated from the XRD data and found to be 5.94, 6.75, 6.88, and 7.19 Å, respectively. This demonstrates that AlCl3 is incorporated between the polycarbosilzane chains and has caused chain–chain expansion. The thermal properties of these AlCSZs were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). They are air stable white solids but decompose in water forming the corresponding dimethylsiloxane, ethylenediamine, and aluminum oxide.

Pyrimidin‐/thiazol‐/thiazolin‐ylidenamidothiophosphoric dichlorides

AbstractNine new amidodichlorothiophosphorus(V) derivatives incorporating pyrimidine, thiazole, and thiazoline rings were obtained by sulfurization of the corresponding aminodichlorophosphines generated in situ from the reaction of the respective N‐alkyl‐2‐aminocycloiminium halide with PCl3 in the presence of triethylamine. These pyrimidin‐/thiazol‐/thiazolin‐ylidenamidothiophosphoric dichlorides were isolated as stable crystalline solids and are well characterized by elemental analysis, NMR, and mass spectroscopy. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:498–502, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10170

A bifunctional calixarene designed for immobilisation on a natural polymer and for metal complexation

The present work describes the multi-step synthesis of a new bifunctional calix[4]arene designed for grafting on natural polymeric materials, such as water-soluble dextrans, and for metal complexation. The podand was then anchored to the polymer by means of a cyanuric linker. The resulting material showed an interesting ability to complex copper(I), giving stable yellowish light orange solids and aqueous solutions.

Loopseal operation of iron ore particles in pneumatic conveying

Loop-seal operation characteristics have been determined in pneumatic conveying (0.078 m ID◊6.0 m high) with iron ore particles (680 μm and 4,500 kg/m 3 ). Solids circulation rates through the loop-seal increase linearly with increasing vertical aeration rate at constant bottom aeration. When the aeration air is injected at the weir section and the lowest point of vertical section, stable higher solids circulation rates are obtained. The solids circulation rates are predicted by using pressure drop measured in fully developed region of riser. The calculated solids circulation rates are in good agreement with the measured values.

Axisymmetric Instability of Fluid Saturated Pervious Cylinders

The emergence of two-phase instability is investigated analytically for the axisymmetric cylinders made of a pervious solid matrix with pores filled with an interstitial fluid. General analytical solutions are derived for a broad range of constitutive models, and are illustrated for a few specific types of solids. For particular combinations of stresses and material moduli, saturated hypoelastic and elastoplastic solids are found to undergo two-phase instability, whereas their dry solid matrices remain stable. Two-phase instability can emerge within stable single-phase solids due to the interaction between solid matrix and fluid flow. The present analysis provides general analytical solutions useful for investigating the instabilities of axisymmetric soil samples subjected to the undrained triaxial tests of geomechanics.

Resonance-stabilized 1,2,3-dithiazolo-1,2,3-dithiazolyls as neutral pi-radical conductors.

Alkylation of the zwitterionic heterocycle 8-chloro-bis[1,2,3]dithiazolo[4,5-b:5',4'-e]pyridine (ClBP) with alkyl triflates affords 8-chloro-4-alkyl-4H-bis[1,2,3]dithiazolo[4,5-b:5',4'-e]pyridin-2-ium triflates [ClBPR][OTf] (R = Me, Et, Pr). Reduction of these salts with decamethylferrocene affords the corresponding ClBPR radicals as thermally stable crystalline solids. The radicals have been characterized in solution by cyclic voltammetry and EPR spectroscopy. Measured electrochemical cell potentials and computed (B3LYP/6-31G) gas-phase disproportionation enthalpies are consistent with a low on-site Coulombic barrier U to charge transfer in the solid state. The crystal structures of ClBPR (R = Me, Et, Pr) have been determined by X-ray crystallography (at 293 K). All three structures consist of slipped pi-stacks of undimerized radicals, with many close intermolecular S.S contacts. ClBPMe undergoes a phase transition at 93 K to a slightly modified slipped pi-stack arrangement, the structure of which has also been established crystallographically (at 25 K). Variable-temperature magnetic and conductivity measurements have been performed, and the results interpreted in light of extended Hückel band calculations. The room-temperature conductivities of ClBPR systems (sigma(RT) approximately 10(-)(5) to 10(-)(6) S cm(-)(1)), as well as the weak 1D ferromagnetism exhibited by ClBPMe, are interpreted in terms of weak intermolecular overlap along the pi-stacks. The latter is caused by slippage of the molecular plates, a feature necessitated by the steric size of the R and Cl groups on the pyridine ring.

Controlled rate thermal analysis commanded by mass spectrometry for studying the kinetics of thermal decomposition of very stable solids

AbstractA quadrupole mass spectrometer coupled to a thermobalance has been used to develop a controlled rate thermal analysis (CRTA) equipment. This instrument maintains constant the partial pressure of the gas generated in a solid–gas reaction during the entire process while recording the weight loss along the process. This system permits to perform the kinetic analysis of the thermal decomposition of very stable compounds with a very low equilibrium pressure in the temperature range at which the reaction takes place. The performance of the equipment was checked by studying the kinetics of the thermal decomposition of BaCO3 using for the control the CO2 partial pressure. Both the activation energy and the reaction kinetic model has been calculated. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 184–192, 2002; DOI 10.1002/kin.10042

Aquatic chemistry and solubility phenomena of actinide oxides/hydroxides

Abstract The present paper gives an overview of the solubility behavior of actinide oxides/hydroxides, taking into account hydrolysis reactions up to colloid formation. The analogies, systematic trends, and differences in the hydrolysis and solubility constants of actinides in the oxidation states An(III) to An(VI) correlate with the charge and size of the actinide ions. The formation of amorphous and crystalline solids and the discrepancies between the corresponding experimental solubility data may be explained as an effect of particle size. However, using thermodynamic data for the stable crystalline solids, the predicted solubilities are often significantly lower than experimental data (even in long-time experiments), indicating that the solubility is controlled by the surface properties. Typical examples are the known U(VI) solids schoepite and sodium diuranate. The most striking example is provided by the tetravalent actinides. Above the threshold of hydrolysis, the dissolution of microcrystalline or crystalline An(IV) oxides is found to be irreversible. The measured concentrations approach those of the amorphous hydroxides or hydrous oxides.

Temperature Induced Bridge Flocculation of Aqueous Zirconia Suspensions in the Presence of Polyacrylic Acid.

Temperature-induced bridge flocculation of aqueous zirconia suspensions in the presence of polyacrylic acid (PAA) has been studied. The viscosity (20 vol%) of zirconia suspensions with different concentrations of PAA as a function of temperature was measured. The results showed that the viscosity of the suspension in the absence of PAA suddenly increased with increasing temperature above 35°C due to the depletion of zirconium and yttrium cations. In contrast, heating the suspension over 45°C in the presence of PAA led to a sudden increase in viscosity, which can be rationalized by considering the increase in the ionic strength of the suspension as a result of leaching of both yttrium and zirconium cations and also the extent of adsorption of the PAA on the suspension particles. To confirm the bridge flocculation or gelation of the zirconia suspensions in the presence of PAA, viscoelastic measurements in terms of complex, storage and loss moduli (G* and G' and G, respectively) as a function of temperature were studied. Preliminary tests on temperature-induced bridge flocculation of high solid suspension (40 vol%) in the presence of PAA were also carried out. It was found that with increasing the temperature up to 85°C, the height stability of the samples reached to an optimum level and no deformation was detected. To reach the optimum stability for the samples at lower temperatures, the polymer dosage must be increased. G*, G' and G of high solid suspensions (40 vol%) were measured to evaluate the gel formation. The abrupt changes of G* and G' values from < 50 kPa to about 300 kPa, where G was approximately constant at <50 kPa at ∼55°C, can be taken to indicate the formation of gel-like stable solids.

Characterization and electrochemical study of bis(ferrocenes) with a furan spacer and ferrocenophanes prepared from α-bromoacetyl substituted ferrocenes

The bis(ferrocene) derivative 3-bromo-2,4-bis(ferrocenyl)furan ( 3) was prepared from α-bromoacetylferrocene ( 1) by basic treatment. The heterotrimetallic complex 7 containing two ferrocene moieties and Pd(II) was synthesized by oxidative addition of 3 with a zerovalent palladium precursor. These stable solids were characterized throroughly by spectroscopic means and electrochemical methods (CV and DPV). The new [4]-ferrocenophane ( 8), with all sp 2C bridges was prepared easily from 1,1′-bis(α-bromoacetyl)ferrocene ( 2) by treatment with K t BuO whereas the reaction with Na 2S provides a mixture of 3-thia-[5]ferrocenophane ( 9), as the major product, and [5,5]ferrocenophane ( 10), as the minor product.

Aging of copper pipes by drinking water

Thermodynamic models were used to correlate experimental and field data for the concentrations of copper (Cu), anions, and cations in drinking water with Cu‐containing scales on the inner walls of pipes. This study focused special attention on the aging processes of these scales. Precipitation and dissolution were predicted to be the main aging causes for Cu scales present on the inner walls of pipes. When data were grouped by the solid that controls solubility, the average 8‐h stagnant Cu concentration in drinking water was found to decrease linearly with average pipe age. For these average values, langite was the most soluble and youngest film, followed in both solubility and age by cupric hydroxide, azurite, brochantite, malachite, and tenorite. The more stable solids—malachite and tenorite—were 8 and 16 times less soluble, respectively, than the most soluble solid, langite. Scales usually contained more than one compound, a finding that was attributed to temperature changes, variability of water composition, long stagnation periods, and aging. During the aging process, parts of a young scale surface area may be covered and blocked for further reaction by a precipitate. During long stagnation periods, such factors as changes in pH, oxygen, and carbon dioxide concentrations and precipitation of calcium solids may induce a different Cu compound precipitate.