Stereochemistry of reactions in the 1,2-dimethylsilacyclopentane ring systems. I. Stereospecific transformations

Preparations, separations of geometric isomers, and structural assignments based on nmr and on chemical evidence are described for a number of 1-substituted 1,2-dimethylsilacyclopentanes. A number of stereospecific reactions have been observed, and the stereochemistry is in all cases the same as that observed for acyclic silanes. A discussion of the role of ring strain in determining stereochemical outcome and reaction rates is presented.     

Electrochemical synthesis of polypyrrole/poly-N-(p-nitrophenyl)pyrrole co-polymer

Copolymers of pyrrole and N-(p-nitrophenyl)pyrrole have been synthesized electrochemically. Cyclic voltammetric studies show that the electroactivities of both nitrobenzene and polypyrrole are apparent in the copolymer. Growth of poly-N-(p-nitrophenyl)pyrrole films is self-limiting an stops at 200 to 300 nm. Copolymerization allows thick and freestanding films incorporating the nitrophenyl moiety to be grown.     

The carvoxime system: IV. heat capacities and enthalpies of melting of dl-carvoxime, l-carvoxime and standard n-heptane

Heat capacities between 160 and 385 K and enthalpies of melting of dl-carvoxime and l-carvoxime were determined by adiabatic calorimetry. The performance of the apparatus was checked on standard n-heptane. The enthalpy of melting values are dl-carvoxime, 22.70 ± 0.06; l-carvoxime, 17.02 ± 0.02; n-heptane, 14.059 ± 0.010 kJ mol⁻¹.     

A simple synthesis and purification of 1-ferrocenylalkyl alcohols

An alternative method for the preparation of 1-ferrocenylalkyl alcohols has been developed. This involves condensation of ferrocene with carbonyl compounds in concentrated sulfuric acid and addition of the resulting solutions of 1-ferrocenylalkylium ions into aqueous sodium bicarbonate. The mixtures are then treated with thioglycolic acid and the S-(1-ferrocenylalkyl)thioglycolic acids purified via sodium salts and hydrolysed in the presence of copper powder to give 1-ferrocenylalkyl alcohols in good yields.     

The electrochemical reduction of some fused ring systems

The electrochemical reduction of some fused ring systems containing four carbonyl moieties has been studied in alcoholic aqueous media. A mechanism has been proposed and clarified in which one carbonyl is reduced to a methylene group via an uptake of four electrons.     

A facile synthesis of symmetrical secondary amines from primary amines promoted by the homogeneous catalyst RuCl2(Ph3P)3

Primary amines bearing an α-hydrogen atom are quantitatively converted to symmetrical secondary amines by heating at 185°C for 5 h in the presence of a catalytic amount of RuCl₂(Ph₃)₃.     

An X-ray diffraction study of the SrBrxI2−x system

The mixed halogen phases SrBr_xI_2?x, for which 2.00 > x > 0 were prepared both by heating weighed masses of pure SrBr₂ and SrI₂ in sealed evacuated quartz ampoules and by cocrystallization from absolute ethanol. The reaction products were examined by X-ray powder diffraction methods. Five distinct regions were observed in the phase diagram. The crystallographic characteristics of phases representative of the single phase regions, SrBr₂SrBr_1.60I_0.40, SrBr_1.40I_0.60SrBr_0.80I_1.20, and SrBr_0.30I_1.70SrI₂, are presented, and the anion distributions in the crystal structures are deduced on the basis of X-ray powder diffraction intensities.     

Preparation and characterization of the system BaBrxCl2−x: The structure of BaBrCl

The variations in the lattice parameters in the BaBr_xCl_2?x system have been determined for the composition range 2.0 > x > 0.0. All phases exhibit the PbCl₂-type orthorhombic structure and are assignable to space group Pnma. The crystallographic parameters of BaBrCl were determined by the Rietveld method from a line profile analysis of a digitized powder X-ray diffraction pattern. The anions are ordered with the bromide ion occupying the square pyramidal hole, and the chloride ion the smaller tetrahedral hole. Atomic coordinates are presented.     

ansa-Metallocene derivatives: VIII. Syntheses and crystal structures of ethylene-bridged titanocene and zirconocene derivatives with permethylated ring ligands

Ethylene-bridged titanocene and zirconocene derivatives with permethylated ring ligands, C₂H₄(C₅(CH₃)₄)₂TiCl₂ and C₂H₄(C₅(CH₃)₄)₂ZrCl₂, have been synthesized and their crystal structures determined.     

Calcium alkoxyalanates : II. Advances in the synthesis

Simple syntheses of calcium alkoxyalanates starting from NaAlH₄, CaCl₂ and alcohols involving evolution of hydrogen and separation of sodium chloride are reported. More complex methods, which allow the preparation of calcium alkoxyllalanates without loss of hydride hydrogen from NaAlH₄, CaCl₂, NaOR and AlX₃ (X = OR, Cl) have also been developed.     

Ambient pressure synthesis,properties, and structure refinements of VP4 and CoP2

The previously reported compounds VP₄ and CoP₂, prepared at high pressure, were synthesized in well-crystallized form at ambient pressure by reaction of the elemental components in the presence of iodine. Their structures were refined from single-crystal X-ray diffractometer data to conventional residuals of R = 0.033 for VP₄ (CrP₄ type structure, 11 variables, 815 F values) and R = 0.019 for CoP₂ (arsenopyrite structure, 14 variables, 932 F values). VP₄ is paramagnetic and a metallic conductor. CoP₂ is a diamagnetic semiconductor with an activation energy of 0.34 eV. Chemical bonding and potential displacive phase transitions of these compounds are discussed.     

Studies on the compounds in the BaFeS system. I. Linear chain antiferromagnetism of Ba2FeS3 and related compounds Ba2CoS3 and Ba2MnS3

Magnetic susceptibilities of Ba₂FeS₃, Ba₂CoS₃, and Ba₂MnS₃ show rounded maxima at 130, 125, and 100 K, respectively, which are due to quasi-one-dimensional antiferromagnetic short-range ordering. Intrachain interactions, $\text{J}\text{k}$, are estimated to be ?20, ?15, and ?12 K, respectively. ⁵⁷Fe Mössbauer spectra of Ba₂FeS₃ and ⁵⁷Fe-doped Ba₂CoS₃ and Ba₂MnS₃ at 4.2 K show long-range antiferromagnetic ordering, due to the interchain interaction. The profile of Mössbauer spectra at 4.2 K is analyzed based on the coexistence of magnetic hyperfine and quadrupole interactions, and magnetic hyperfine fields at 4.2 K are estimated to be 36, 29, and 59 kOe, respectively.     

Cationic cobalt(I) carbonyl complexes containing secondary or tertiary phosphines. A direct synthesis from cobalt(II) salts

Cobalt(I) carbonyl complexes of formula [Co(CO)_n(P)_5?n]ClO₄ (n = 1, 2, 3; P = secondary or tertiary phosphine) have been prepared by reaction of CO under ambient conditions with Co(ClO₄)₂ · 6H₂O and phosphine in isopropyl alcohol. The chemical and spectroscopic properties of these complexes are described and the stoichiometry and mechanism of the carbonylation reaction discussed.     

Localized moments in the superconducting Li1+xTi2−xO4 spinel system

Electron spin resonance (ESR) and magnetic-susceptibility measurements on the Li_1+xTi_2?xO₄ spinel system ($\text{0 ≤ x ≤}\text{1}\text{3}$) indicate the presence of two types of localized moments in this material. In both cases, an unpaired electron is trapped as a Ti³⁺ ion in a crystal field that is predominantly octahedral, but with a strong tetragonal component. This type of crystal field cannot arise in the stoichiometric spinel. We propose two types of defect in the title spinel system: an oxygen vacancy and a hydroxyl ion. Unpaired electrons are trapped as Ti³⁺ ions adjacent to these defects, and it is argued that the strong tetragonal field is associated with the formation of a static (TiO)⁺ ion by a displacement of the titanium ion from the defect. Spin relaxation occurs via a thermal ionization of the trapped electron that appears to be associated with a static-dynamic transition in the titanium-ion displacement.