Synthesis, structure and spectroscopic studies on hydroxo-bridged heterotrinuclear complexes of cobalt(m) with ethane-l,2-diamine and ammonia as terminal ligands

Hydroxo-bridged homo- and hetero-trinuclear cobalt(III) complexes of the type [MII(H2O)2{(OH)2CoIII(N4)}2]X2·nH2O [MII= a divalent metal ion such as CoII, NiII or ZnII; N4=(en)2(en = ethane-1,2-diamine) or (NH3)4; X = SO4 or (ClO4)2; n= 3 or 5] have been prepared and spectroscopically characterized. The structure of [Cu{(OH)2Co(en)2}2][SO4]2·2H2O 1 has been determined. The geometry around copper atom is a pseudo-square-based pyramid, with the basal sites occupied by four bridging hydroxide oxygens and the apical site is occupied by a weakly co-ordinated sulfate anion [Cu–O 2.516(4)Å]. The hydroxo groups bridge pairs of cobalt(III) ions which are in near-octahedral environments. The ethylenediamine chelate rings have the twist conformation. In the crystal structure of [Cu{(OH)2Co(en)2}2][ClO4]4·2H2O 2 the perchlorate ion is not co-ordinated and the en ligands have envelope conformations. The sulfate ion in [Cu{(OH)2Co(NH3)4}2][SO4]2·4H2O 3 is not co-ordinated to the central copper ion. Electronic, infrared and variable-temperature EPR spectral data are discussed.

4-[2-(1-Acetyl-2-oxopropylidene)-hydrazino]-N-(pyrimidin-2-yl)benzenesulfonamide

In the title compound, C15H15N5O4S, the dihedral angle between the pyrimidine and benzene rings is 84.56 (2)degrees. Intramolecular hydrazine-carbonyl N-H center dot center dot center dot O and intermolecular sulfonamide-pyridimine N-H center dot center dot center dot N hydrogen bonds stabilize the molecular and crystal structures, respectively.

Amide-catalysed isomerisation of 5,6-dihydroisoquinolines: a novel synthesis of 1,2-dihydroisoquinolines

Knoevenagel condensation of 2-acylcyclohexanones or 2-ethoxycarbonylcyclohexanone with either cyanoacetamide or malononitrile followed by silver salt alkylation gave the 5,6,7,8-tetrahydroisoquinolines (3a–i). Chromic acid oxidation of the 5,6,7,8-tetrahydroisoquinolines (3a–i) to the corresponding tetralones (4a–i) followed by sodium borohydride reduction and p-toluenesulphonic acid-catalysed dehydration of the resulting alcohols (5a–i) gave the 5,6-dihydroisoquinolines (6a–i). Reaction of 5,6-dihydroisoquinolines (6a–g) with potassium amide in liquid ammonia gave a mixture of the 1,3-dihydroisoquinolines (7a–g) and the isoquinolines (8a–g). The C-1 unsubstituted 1,2-dihydroisoquinoline (7c) was found to be very unstable. In the case of the 5,6-dihydroisoquinolines (6h and 6i), reaction of potassium amide in liquid ammonia resulted in a mixture of 1-aminoisoquinoline (9) and the isoquinolines (8h and 8i). All the above compounds have been characterised by spectral data. A probable pathway for the formation of the 1,2-dihydroisoquinolines (7a–g) and the isoquinolines (8a–i) is suggested.

Amide-catalysed isomerisation of 5,6-dihydroisoquinolines: a novel synthesis of 1,2-dihydroisoquinolines

Knoevenagel condensation of 2-acylcyclohexanones or 2-ethoxycarbonylcyclohexanone with either cyanoacetamide or malononitrile followed by silver salt alkylation gave the 5,6,7,8-tetrahydroisoquinolines (3a–i). Chromic acid oxidation of the 5,6,7,8-tetrahydroisoquinolines (3a–i) to the corresponding tetralones (4a–i) followed by sodium borohydride reduction and p-toluenesulphonic acid-catalysed dehydration of the resulting alcohols (5a–i) gave the 5,6-dihydroisoquinolines (6a–i). Reaction of 5,6-dihydroisoquinolines (6a–g) with potassium amide in liquid ammonia gave a mixture of the 1,3-dihydroisoquinolines (7a–g) and the isoquinolines (8a–g). The C-1 unsubstituted 1,2-dihydroisoquinoline (7c) was found to be very unstable. In the case of the 5,6-dihydroisoquinolines (6h and 6i), reaction of potassium amide in liquid ammonia resulted in a mixture of 1-aminoisoquinoline (9) and the isoquinolines (8h and 8i). All the above compounds have been characterised by spectral data. A probable pathway for the formation of the 1,2-dihydroisoquinolines (7a–g) and the isoquinolines (8a–i) is suggested.

Novel coordination behaviour of gem-bis (pyrazolyl) cyclotriphosphazenes as tridentate NNN-donor ligands: The crystal structure of [Mo(CO)3{N3P3Ph4(3,5-Me2C3HN2)2}]

Reactions of group 6 metal carbonyls with bis(pyrazolyl) phosphazenes yield metal tricarbonyl complexes, [M(CO)3.L] [L = N3P3Ph4 (3, 5-Me2C3HN2)2 (1) or N3P3(MeNCH2CH2O)2 (3,5-Me2C3HN2)2(4)]. The structure of the complex [Mo(CO)3.1], determined by single-crystal X-ray analysis, shows that the (pyrazolyl) phosphazene acts as a tridentate ligand; the two pyridinic pyrazolyl nitrogen atoms and a phosphazene ring nitrogen atom are coordinated to the metal. A similar structure is proposed for the complexes [M(CO)3.4] (M = Mo or W] on the basis of their spectroscopic data.

Hydrazine carboxylate precursors to fine particle titania, zirconia and zirconium titanate

Titanyl hydrazine carboxylate dihydrate, TiO(N2H3COO)2.2H2O, zirconyl hydrazine carboxylate dihydrate, ZrO(N2H3COO)2.2H2O and their solid solution, ZrTiO2(N2H3COO)4.4H2O have been prepared for the first time and investigated as precursors to fine particle TiO2, ZrO2 and ZrTiO4 respectively. Titania(anatase) formed has a very high surface area of 110 m2/g and zirconium titanate showed very low dielectric loss (4 x 10(-4)).

Nitride synthesis using ammonia and hydrazine - a thermodynamic panorama

Because of the wide variety of projected applications of ultrapure nitrides in advanced technologies, there is interest in developing new cost-effective methods of synthesis. Explored in this study is the use of ammonia and hydrazine for the synthesis of nitrides from oxides, sulfides and chlorides. Even when the standard Gibbs energy change for the nitridation reactions involved are moderately positive, the reaction can be made to proceed by lowering the partial pressure of the product gas below its equilibrium value. Use of a metastable form of precursor in the nanometric size range is an alternative method to facilitate nitridation. Ellingham-Richardson-Jeffes diagrams are used for a panoramic presentation of the driving force for each set of reactions as a function of temperature. Oxides are the least promising precursors for nitride synthesis; sulfides offer a larger synthetic window for many useful nitrides such as BN, AlN, InN, VN, TiN, ThN and Si3N4. The standard Gibbs free energy changes for reactions involving chlorides with either ammonia or hydrazine are much more negative. Hydrazine is a more powerful nitriding agent than ammonia. The metastability of hydrazine requires that it be introduced into a reactor through a water-cooled lance. The use of volatile halides with ammonia or hydrazine offers the potential for synthesis of pure and doped nanocrystalline nitrides. Nitride thin films can also be prepared by suitable adaptations of the chloride route. (C) 2002 Kluwer Academic Publishers.

Self-assembly of Ru-4 and Ru-8 assemblies by coordination using organometallic Ru(II)(2) precursors: Synthesis, characterization and properties

Coordination-driven self-assembly of binuclear half-sandwich p-cymene ruthenium(II) complexes [Ru-2(mu-eta(4)-C2O4)(MeOH)(2)(eta(6)-p-cymene)(2)](O3SCF3)(2) (1a) or [Ru-2(mu-eta(4)-N,N'-diphenyloxamidato)(MeOH)(2)(eta(6)-p-cymene)(2)]( O3SCF3)(2) (1b) separately with an imidazole-based tetratopic donor L in methanol affords two tetranuclear metallamacrocycles 2a and 2b, respectively. Conversely, the similar combination of L with 2,5-dihydroxy-1,4-benzoquinonato (dhbq) bridged binuclear complex [Ru-2(mu-eta(C6H2O4)-C-4)(MeOH)(2)(eta(6)-p-cymene)(2)](O3SCF3)(2) (1c) in 1:2 molar ratio resulted in an octanuclear macrocyclic cage 2c. All the self-assembled macrocycles 2a-2c were isolated as their triflate salts in high yields and were characterized fully by multinuclear (H-1, C-13 and F-19) NMR, infrared (IR) and electrospray ionization mass spectrometry (ESIMS). In addition, the molecular structure of macrocycle 2a was established unequivocally by single-crystal X-ray diffraction analysis and adopts a tetranuclear rectangular geometry with the dimensions of 5.53 angstrom x 12.39 angstrom. Furthermore, the photo-and electrochemical properties of these newly synthesized assemblies have been studied by using UV-vis absorption and cyclic voltammetry analysis.

Mossbauer-Effect Study Of The Thermal-Decomposition In Hydrogen Of Homogeneously Mixed Ferrous Nickel Oxalates With Different Iron To Nickel Ratios

Mossbauer effect and X-ray measurements are carried out on product samples of the thermogravimetric analysis (TGA) and isothermal decomposition in hydrogen of homogeneously mixed ferrous nickel oxalates with different iron to nickel ratios. The formation of Fe-Ni alloy is obtained at considerably lower temperatures (z 300 "C) in each case. The Fe-Ni alloys obtained shift from iron-rich to nickel-rich composition as the nickel ratio in the mixed metal oxalates is increased. The formation of Pe-Ni Invar from mixed metal oxalate with Fe:Ni = 1:l is indicated in the early stages but not from those with Fe:Ni = 2: 1 or 64:36. An Produktproben von homogen verteilten Eisen-Nickeloxalaten mit unterschiedlichem Eisen- Nickel-Verhaltnis nach thermogravimetrischer Analyse (TGA) und isothermem Zerfall in Wasserst off werden Mollbauereffekt- und Rontgenmessnngen durchgefuhrt. In allen Fiillen wird die Bildung der Fe-Ni-Legierung bei betriichtlich niedrigeren Temperaturen (= 300 "C) erhalten. Die erhaltenen Fe-Ni-Legierungen verschieben sich von der eisenreichen zur nickelreichen Zusrtmmensetzung, wenn das Nickelverhaltnis in dem BIetall-Mischoxalat erhoht wird. Die Bildung der Fe-Ni-lnvar-Legierung aus dem Metall-Mischoxalat mit Fe:Ni = 1 : 1 wird in fruhen Zu Zustanden beobachtet, iedoch nicht aus Oxalaten mit Fe:Ni = 2:1 oder 64:36.

Noble Metal Ionic Catalysts

Because of growing environmental concerns and increasingly stringent regulations governing auto emissions, new more efficient exhaust catalysts are needed to reduce the amount of pollutants released from internal combustion engines. To accomplish this goal, the major pollutants in exhaust-CO, NOx, and unburned hydrocarbons-need to be fully converted to CO2, N-2, and H2O. Most exhaust catalysts contain nanocrystalline noble metals (Pt, Pd, Rh) dispersed on oxide supports such as Al2O3 or SiO2 promoted by CeO2. However, in conventional catalysts, only the surface atoms of the noble metal particles serve as adsorption sites, and even in 4-6 nm metal particles, only 1/4 to 1/5 of the total noble metal atoms are utilized for catalytic conversion. The complete dispersion of noble metals can be achieved only as ions within an oxide support. In this Account, we describe a novel solution to this dispersion problem: a new solution combustion method for synthesizing dispersed noble metal ionic catalysts. We have synthesized nanocrystalline, single-phase Ce1-xMxO2-delta and Ce1-x-yTiyMxO2-delta (M = Pt, Pd, Rh; x = 0,01-0.02, delta approximate to x, y = 0.15-0.25) oxides in fluorite structure, In these oxide catalysts, pt(2+), Pd2+, or Rh3+ ions are substituted only to the extent of 1-2% of Ce4+ ion. Lower-valent noble metal ion substitution in CeO2 creates oxygen vacancies. Reducing molecules (CO, H-2, NH3) are adsorbed onto electron-deficient noble metal ions, while oxidizing (02, NO) molecules are absorbed onto electron-rich oxide ion vacancy sites. The rates of CO and hydrocarbon oxidation and NOx reduction (with >80% N-2 selectivity) are 15-30 times higher in the presence of these ionic catalysts than when the same amount of noble metal loaded on an oxide support is used. Catalysts with palladium ion dispersed in CeO2 or Ce1-xTixO2 were far superior to Pt or Rh ionic catalysts. Therefore, we have demonstrated that the more expensive Pt and Rh metals are not necessary in exhaust catalysts. We have also grown these nanocrystalline ionic catalysts on ceramic cordierite and have reproduced the results we observed in powder material on the honeycomb catalytic converter. Oxygen in a CeO2 lattice is activated by the substitution of Ti ion, as well as noble metal ions. Because this substitution creates longer Ti-O and M-O bonds relative to the average Ce-O bond within the lattice, the materials facilitate high oxygen storage and release. The interaction among M-0/Mn+, Ce4+/Ce3+, and Ti4+/Ti3+ redox couples leads to the promoting action of CeO2, activation of lattice oxygen and high oxygen storage capacity, metal support interaction, and high rates of catalytic activity in exhaust catalysis.

Mossbauer Effect Study of the Thermal Decomposition in Hydrogen of Homogeneously Mixed Ferrous Nickel Oxalates with Different Iron to Nickel Ratios

Mossbauer effect and X-ray measurements are carried out on product samples of the thermogravimetric analysis (TGA) and isothermal decomposition in hydrogen of homogeneously mixed ferrous nickel oxalates with different iron to nickel ratios. The formation of Fe-Ni alloy is obtained at considerably lower temperatures (z 300 "C) in each case. The Fe-Ni alloys obtained shift from iron-rich to nickel-rich composition as the nickel ratio in the mixed metal oxalates is increased. The formation of Pe-Ni Invar from mixed metal oxalate with Fe:Ni = 1:l is indicated in the early stages but not from those with Fe:Ni = 2: 1 or 64:36. An Produktproben von homogen verteilten Eisen-Nickeloxalaten mit unterschiedlichem Eisen- Nickel-Verhaltnis nach thermogravimetrischer Analyse (TGA) und isothermem Zerfall in Wasserstoff werden Mollbauereffekt- und Rontgenmessnngen durchgefuhrt. In allen Fiillen wird die Bildung der Fe-Ni-Legierung bei betriichtlich niedrigeren Temperaturen (= 300 "C) erhalten. Die erhaltenen Fe-Ni-Legierungen verschieben sich von der eisenreichen zur nickelreichen Zusrtmmensetzung, wenn das Nickelverhaltnis in dem BIetall-Mischoxalat erhoht wird. Die Bildung der Fe-Ni-lnvar-Legierung aus dem Metall-Mischoxalat mit Fe:Ni = 1 : 1 wird in fruhen Zustanden beobachtet, iedoch nicht aus Oxalaten mit Fe:Ni = 2:1 oder 64:36.

A criterion for existence of low frequency pure surface magnetoplasmon modes in the Faraday configuration

The low frequency surface magnetoplasmon-type polaritons in the Faraday configuration will propagate as generalized surface modes if 4ε∞/(ε∞ − 1)2 greater-or-equal, slanted μ2 and as pure surface modes if this inequality is reversed. The possibility of using the low frequency surface waves as a suitable probe for measuring the carrier concentration of a given sample is discussed.

Precipitation of rutile and anatase (Tio12) fine powders and their conversion to MTiO3 (M = Ba, Sr, Ca) by the hydrothermal method

Fine powders of TiO2 (rutile) with high degree of crystallinity are formed from aqueous titanium oxychloride solution under hydrothermal conditions at 160–230°C and 15–100 kg/cm2 for 1–2 hours. The anatase phase is produced from the same medium when sulfate ion impurity is present, with Image . Both these fine powders are converted to BaTiO3, SrTiO3 or CaTiO3 when suspended in Ba(OH)2 or Sr(OH)2 solution or in an aqueous slurry of carbonate-free CaO with Image , at 180–280°C and 12–65 kg/cm2 for 4–8 hours. The resulting fine powders contain monocrystallites of the perovskite phase with 0.1–1.5 μm particle size.

Spore and crystal formation in Bacillus thuringiensis var thuringiensis during growth in cystine and cysteine.

The effect of the addition of different concentratons of cystine and cysteine on sporulation and parasporal crystal formation in Bacillus thuringiensis var. thuringiensis was studied. The effect was well pronounced when the systine/cysteine additions were made after the stationary phase. Heat stable spores and crystals were formed when the culture was provided with a low concentration of cystine/cysteine (0.05 per cent w/v). At a moderate concentration of cystine or cysteine (0.15%), only heat labile spores were formed without the production of the crystal. When the cystine/cysteine concentration was high (0.25%), spore and crystal formation were completely inhibited. Partial reversal of inhibition of sporulation was brought about by sodium sulphate or zinc sulphate and lead, copper, cadmium or cobalt acetate at 0.2 mM or at 0.2% of sodium or potassium pyruvate, citrate, isaconitate, oxalosuccinate, ∝ -keto-glutarate, succinate, fumarate, malate, or oxalacetate. Glutamate (0.2%) overcame the inhibitory effect of cystine/cysteine completely. The structural changes observed using phase contrast microscopy were dependent upon the concentration of cystine/cysteine.

Succinate and malate improve development of hamster eight-cell embryos in vitro: Confirmation of viability by embryo transfer

The in vitro development of hamster preimplantation embryos is supported by non-glucose energy substrates. To investigate the importance of embryonic metabolism, influence of succinate and malate on the development of hamster 8-cell embryos to blastocysts was examined using a chemically defined protein-free modified hamster embryo culture medium-2 (HECM-2m). There was a dose-dependent influence of succinate on blastocyst development; 0.5 mM succinate was optimal (85.1% ± 3.9 vs. 54.5% ± 3.5). In succinate-supplemented HECM-2m, blastocyst development was reduced by omission of lactate (68.5% ± 7.2), but not pyruvate (85.8% ± 6.2) or glutamine (84.1% ± 2.1). Succinate along with either glutamine or lactate or pyruvate poorly supported blastocyst development (28%-58%). Malate also stimulated blastocyst development; 0.01 mM malate was optimal (86.3% ± 2.8). Supplementation of both succinate and malate to HECM-2m supported maximal (100%) blastocyst development, which was inhibited 4-fold by the addition of glucose/phosphate. The mean cell numbers (MCN) of blastocysts cultured in succinate-supplemented HECM-2m was higher (28.3 ± 1.1) than it was for those cultured in the absence of glutamine or pyruvate (range 20-24). The MCN was the highest (33.4 ± 1.6) for blastocysts cultured in succinate-malate-supplemented HECM-2m followed by those in succinate (28.3 ± 1.1) or malate (24.7 ± 0.5) supplemented HECM-2m. Embryo transfer experiments showed that 29.8% (±4.5) of transferred blastocysts cultured in succinate-malate-supplemented HECM-2m produced live births, similar (P > 0.1) to the control transfers of freshly recovered 8-cells (33.5% ± 2.0) or blastocysts (28.9% ± 3.0). These data show that supplementation of succinate and malate to HECM-2m supports 100% development of hamster 8-cell embryos to high quality viable blastocysts and that non-glucose oxidizable energy substrates are the most preferred components in hamster embryo culture medium. Mol. Reprod. Dev. 47:440-447, 1997. © 1997 Wiley-Liss, Inc.