Magnetic properties of the mixed-valence compounds CaMn3O6 and CaMn4O8

The preparation of two new mixed-valence compounds, CaMn₃O₆ and CaMn₄O₈, are described and their magntic and EPR behavior investigated. The Mn moments in both compounds have nearly spinonly values. CaMn₃O₆ and CaMn₄O₈ order ferrimagnetically near 3 and 89 K, respectively. The broad, Lorentzian EPR lines indicate a significant exchange interaction between Mn³⁺ and Mn⁴⁺ ions. The magnetic and EPR results suggest a strong ferromagnetic interaction between Mn³⁺ and Mn⁴⁺ ions and a comparable antiferromagnetic Mn³⁺Mn³⁺ and/or Mn⁺Mn⁴⁺ interaction.     

Thermodynamics of carbon dioxide and carbonic acid: (a) the standard enthalpies of solution of Na2CO3(s), NaHCO3(s), and CO2(g) in water at 298.15 K; (b) the standard enthalpies of formation,standard Gibbs energies of formation,and standard entropies of CO2(aq), HCO3−(aq), CO32−(aq), NaHCO3(s), Na2CO3(s), Na2CO3·H2O(s), and Na2CO3·10H2O(s)

Enthalpies of solution of CO₂(g), NaHCO₃(s), and Na₂CO₃(s) in excess NaOH solution were measured at 298.15 K by solution calorimetry. The results were reduced to standard-state processes through use of results from a preceding paper, and standard enthalpies of solution for CO₂(g), NaHCO₃(s), and Na₂CO₃(s) in water at 298.15 K were found to be: ?(4720 ± 40), (4474 ± 30), and ?(6371 ± 30) cal_th mol^?1 respectively. The results of equilibrium studies involving CO₂(g) (solubility and e.m.f. studies) were reviewed and assembled,together with entropies for related solids. Standard values of ΔH_f^o, ΔG_f^o, and S^o at 298.15 K were evaluated for CO₂(aq, non-ionized), HCO₃^?(aq), CO₃^2?(aq), NaHCO₃(s), Na₂CO₃(s), Na₂CO₃·H₂O(s), and Na₂CO₃·10H₂O(s).     

Studies of heterocyclic compounds: III. Synthesis and thermal decompositions of some 2-thiophenemercuric derivatives

2-Thiophenemercuric chloride(I), on reaction with sodium or silver thiocyanate, silver azide, silver acetate, and silver trifluoromethanesulfonate gave the 2-thiocyanate (2), 2-azide (4), 2-acetate (5) and 2-trifluoromethanesulfonate (6), respectively. The thermal decompositions of these compounds, together with that of 2,2'-dithienyl mercury, have been studied. The 2-thiophenemercuric triflate (6) decomposes at room temperature to give 2,2'-dithienylmercury. The 2-azide (4), when treated with either cyclohexene or triphenylphosphine, gave only the 2,2'-dithienylmercury. All the 2-thiophenemercuric salts decompose at about 300°C to give only a black insoluble residue. With the aid of some control experiments and comparison with previous work on phenyl- and p-tolyl-mercuric salts, a mechanism is proposed to account for the results.     

Syntheses and properties of H-1,2,3-triazoles

About twenty new H-1,2,3-triazoles (T) were readily synthesized by nucleophilic attack of sodium azide on activated acetylenes in dimethylformamide. Typical activating groups were COR, COOR, O₂NC₆H₄ PO(OC₂H₅, COT, and (C₆H₅)₃P⁺. Propynyl 4-triazolyl ketone or phenylethynyl 4-triazolyl ketone may be converted to acylic adducts (triazolylketoenamines), biheteroaromatic systems (isoxazolytriazoles, pyrazolytriazoles), as well as to ditriazolyl ketones. Certain T properties were examined in detail. The apparent pK′s for our group of ca 30 triazoles were in the range 4·95?9·45 in ethanol-water (v/v 1/1) at 25°. The Hammett correlation for five 4-aryl-T was log K_a = 0·89σ^? ?9·21 and for seven 4-aryl-5-carbethoxy-T was log K_a = 1·45σ?6·95. The UV spectra of T are similar to those of other heteroaromatic and phenyl compounds: interesting analogies between triazolyl and phenyl, e.g., ”ortho“ crowding effects, appear to be indicated in the spectra of compounds related to biphenyl, stilhene and benzophenone. With regard to structure assignment on the basis of spectra, characteristic features of UV and IR spectra of the H-1,2,3-triazoles are discussed.     

Allylbutyltin halides (CH2CHCH2)SnBu3−nCln (n = 0, 1, 2, 3). Preparation,carbon-13 NMR characterization and allylstannylation ability towards ketones and aldehydes

Mixed allylbutyltin halides (CH₂CHCH₂)SnBu_3-nCl_n (n = 0–3) have been prepared, and characterized by carbon-13 NMR spectroscopy. Their ability to bring about allylstannylation of ketones and aldehydes, to form organostannoxy compounds, Bu_3-nSnCl_nOC(R′)(R″)CH₂CHCH₂, has been shown to increase on increasing the value of n, that is on increasing the acceptor ability of the tin centre.     

Preparation and magnetic properties of manganite

A new hydrothermal synthesis of manganite is described, and the magnetic and electron paramagnetic resonance (EPR) behavior of the product is reported. The magnetic susceptibility is nearly independent of temperature above 90°K and increases dramatically on cooling to 30°K. The EPR lineshape, linewidth, and g-factor at 296°K are Lorentzian (in the central region), 280 ± 10 G, and 1.997 ± 0.006, respectively. The EPR spectrum is interpreted in terms of nearly one-dimensional interactions between identical Mn moments. The results of this study support the view that all Mn ions are trivalent and that the magnetic interactions between these ions are nearly one dimensional.     

Syntheses of methyl α-dl-mycaminoside, methyl α-dl-oleandroside, methyl β-dl-cymaroside, methyl α-dl-tyveloside and methyl α-dl-chromoside C

Five rare hexoses, which are components of antibiotics or cardiac glycosides, have been synthesized as methyl glycosides through a common intermediate methyl 2,3-dehydro-2,3,6-trideoxy-α-dl glucopyranoside (7). Epoxidation and subsequent treatment with dimethylamine of7 afforded methyl α-dl-mycaminoside (9). The addition reaction of MeOH to12 gave methyl α-dl-oleandroside (15) and methyl β-dl-cymaroside (17). The hydroxymercuration and subsequent reduction of12 afforded methyl α-dl-chromoside C (19) and methyl β-dl-tyveloside (25).     

Chemistry of organosilicon compounds: CL. Preparation and UV spectra of nitrophenylpolysilanes

Sixp- andm-nitrophenyl-substituted methylpolysilanes have been prepared by the reaction of nitrobenzyne with monohydromethylpolysilanes. UV spectra ofp-nitrophenylpolysilanes revealed a strong red shift compared with the parent phenylpolysilanes due to the contribution of intramolecular charge transfer to the nitro group.     

Ionic conductivity of Li2MgSn3O8 ramsdellite

The ionic conductivity of polycrystalline pellets of Li₂MgSn₃O₈ with ramsdellite-type structure was measured by complex impedance technique. The conductivity is 1.2 × 10^?8 (Ω cm)^?1 at 300°C and 2.3 × 10^?4 (Ω cm)^?1 at 450°C. The results are discussed in relation to structural properties.     

Über Ordnungs-Unordnungsphänomene bei Sauerstoff perowskiten vom Typ A2+3B2+M5+2O9

Perovskites of the type A²⁺₃B²⁺M⁵⁺₂O₉, where A²⁺ = Ba, Sr; B²⁺ = Mn, Co, Ni, Zn; M⁵⁺ = Nb, Ta, show order-disorder phenomena. At lower temperatures a thermodynamically unstable disordered cubic perovskite is formed ($\text{1}\text{3}$ formula unit—$\text{AB}{}_{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{M}{}_{\mathrm{<mtext>2</mtext><mtext>3</mtext>}}\text{O}{}_3$—in the cell), which transforms irreversibly into a 1: 2 ordered high-temperature form with 3L structure (sequence (c)₃). For A²⁺ = Ba this lattice is hexagonal (space group $\text{P}\text{3}\text{m1}$; one formula unit in the cell); with A²⁺ = Sr a triclinic distortion is observed. For Ba₃CoNb₂O₉ a second transformation into a cubic disordered perovskite takes place at 1500°C. This transition is reversible and of the order-disorder type. The vibrational and diffuse reflectance spectra are discussed.     

Oxygen evolution on SrFeO3 electrode

Oxygen evolution reactions on SrFeO₃ were investigated in alkaline and acidic solutions. It was found that the catalytic activity for the oxygen evolution reaction in the alkaline solution is high. The following reaction steps (V)+Fe+2H₂O→(O)+FeOH₂+2H⁺+2e^? in acidic solution and FeOH+OH^?→FeO^?+H₂O in alkaline solution are presumed to be rate-controlling in the anodic evolution of oxygen on SrFeO₃ electrode, where (V) denotes oxygen vacancy on the electrode surface. The reaction mechanism and the catalytic property are discussed in connection to the band structure of the oxide.     

Studies of acenaphthene derivatives—XXVIII : The reaction of 2-diazoacenaphthenone with anils in the presence of boron trifluoride

Reaction of 2-diazoacenaphthenone with anils in the presence of a catalytic amount of boron trifluoride etherate is reported. The diazoketone reacts with benzylidenanilines to afford a mixture of stereoisomers of spiro[acenaphthenone-2′,4-imidazolidine], whose structures correspond to compounds derived from 1:2 adducts of the diazoketone and anils with the elimination of nitrogen. A pathway involving spiro-aziridine intermediates is proposed for their formation. Reaction of the diazoketone with aα-alkylbenzylidenanilines however gives the corresponding acenaphtho[1,2-b]pyrroles, whose structures correspond to compounds arising from 1:1 adducts with the elimination of both nitrogen and water. The reaction of the tautomeric enamine form of the anil with a carbenoid intermediate generated from the diazoketone is suggested for pyrrole formation.     

Cation transport at 25°c from binary Tl+Mn+ and K+Mn+ nitrate mixtures in a H2OCHCl3H2O liquid membrane system containing a series of macrocyclic polyether carriers

Carrier-mediated cation fluxes were determined using a H₂OCHC1₃H₂O liquid merebrane system for TlNO₃ and for binary mixtures of either TlNO₃ or KNO₃ with alkali metal ions, alkaline earth metal ions, and Pb²⁺ (in the case of TlNO₃). Both macrocyclic polyether and cryptand ligands were used as carriers. In Tl⁺Mⁿ⁺ mixtures, selective transport of Tl⁺ was found over all cations studied, except in the cases of Ag⁺ by 2.2 and of Pb²⁺ by 18C6, DC18C6, ClDKP18C6, and 2.2. Generally, K⁺ was transported selectively from K⁺Mⁿ⁺ mixtures, except in the cases of K⁺Tl⁺ mixtures in which Tl⁺ was transported selectively in all cases. A model relating cation flux to log K(CH₃OH) for Mⁿ⁺—macrocycle interaction and to ion-partitioning between the organic and aqueous phases was successful in rationalizing selective cation transport in most of the systems studied.     

X-ray and mössbauer studies of tricyclohexyltin(IV) halides. The crystal structures of (cyclo-C6H11)3SnX (X = F,Br and I)

The structures of tricyclohexyltin fluoride (I), bromide (II) and iodide (III) have been determined by X-ray analysis. Compound I crystallizes in the space group P2₁/m with a = 10.422(6), b = 17.238(9), c = 5.769(3) Å, β = 104.6(1)° and Z = 2. Compounds II and III crystallize in the space group Pcmn with a = 10.427(6), b = 16.914(9), c = 11.366(6) Å, Z = 4; and a = 10.400(6), b = 16.900(10), c = 11.400(4) Å, Z = 4, respectively. All three structures consist of discrete tetrahedral (cyclo-C₆H₁₁)₃SnX units.The temperature dependence of the Mössbauer resonance areas has been examined in order to obtain information about the relationship between chemical structure and lattice dynamics.     

Phase distribution in the HfO2Er2O3Ta2O5 system

Phase relationships obtained by heating coprecipitated oxide powders in the HfO₂Er₂O₃Ta₂O₅ system were investigated by X-ray diffractometry. Partial isothermal sections at 1100 and 1500°C are presented.     

Synthesis and properties of monocyclopentadienyltitanium compounds

The pentacoordinated complexes (RCp)TiCl₂(acac) (R = H, Me, Ph₂CH) have been prepared by photolysis of (RCp)₂TiCl₂ and acetylacetone in THF and the hexacoordinated compounds (RCp)TiCl(acac)₂ by the reaction of (RCp)₂TiCl₂ and acetylacetone in the presence of triethylamine in isobutyronitrile. The hexacoordinated complexes (RCp)TiCl(oq)₂ (R = H, Me, Ph₂CH; oq = 8-oxyquinolate) have been prepared by the direct interaction of (RCp)₂TiCl₂ and 8-hydroxyquinoline in isobutyronitrile; these compounds can be obtained more quickly by photolysis of the same starting materials in THF solution.     

Organoboron compounds XIII. Preparation and properties of some 2-substituted 1,3,2-dithiaborinans

The preparation and properties of some boron heterocycles of the general formula

(where X = Ph, SR, NR₂, NHR and NHNPh) are described and the general features of their mass spectra discussed.     

18-Deoxyaldosterone,its chemical and microbial reduction products

Reduction of the diketal 1 with sodium aluminum bis-(methoxyethoxy) hydride afforded the crystalline 18-hydroxycorticosterone diketal (2), an intermediate in the formation of 18-deoxyaldosterone acetate (4b). The hitherto unreported but anticipated metabolites of 4 were prepared as follows: hydrogenations of 4b furnished the fα- and 5β isomers 6 and 5b, and thence the tetra- and hexahydro derivatives 10, 11, 8, 9 and 7, and the 3-deoxy compounds 12 and 13. Anaerobic fermentations of 4b with Clostridium paraputrificum gave the tetrahydro derivative 8b in high yield.