The effect of catalysts on the decomposition of trisethylene diamine chromium(III) trichloride

Journal of Thermal Analysis and Calorimetry - The thermal decomposition of trisethylene diamine chromium(III) trichloride in an inert atmosphere has been shown to be catalysed by ammonium chloride...     

The thermal decomposition of alkaline earth formates

The thermal decomposition of alkaline earth formates has been studied. Experiments with single crystals, compacts and powders of strontium formate demonstrate that the method of sample presentation can affect the rate of decomposition.For anhydrous calcuim, strontium and barium formates, isothermal kinetic runs show that the decompositions follow the Erofeev law, In(l-α) = ktⁿ; the measured activation energies were 199.4, 228 and 270 kJ/mol respectively.     

Thermodynamics for Coulomb systems: A problem at vanishing particle densities

In this paper I combine techniques recently developed by Charles Fefferman with the well-known methods of Joel Lebowitz and Elliott Lieb to resolve some technical problems left unsettled by Lebowitz and Lieb's fundamental 1972 paper The constitution of matter: Existence of thermodynamics for systems composed of electrons and nuclei.     

The chemistry of phosphole derivatives

Synthetic approaches to, and the chemistry of, phospholes, benzophospholes and dibenzophospholes are reviewed and particular attention is paid to the possible aromatic character of the phosphole ring. Systems containing the 2H- and 3H-phosph(V)ole nucleus are surveyed as are phosphole derivatives containing pentacovalent and six-coordinate phosphorus. Stereochemical considerations in the more complex phosphole derivatives are discussed.     

A quantum-mechanical study of the lone-pairs in H2O and H2S

It is shown from SCF-MO studies using localised orbitals that the angles between the lone-pairs in H₂O and H₂S are 115° and 127°, in agreement with the qualitative predictions of the Sidgwick-Powell theory.     

Reactions of C(6)F(5)Li with tetracyclone and 3-ferrocenyl-2,4, 5-triphenylcyclopentadienone: An (19)F NMR and X-ray crystallographic study of hindered pentafluorophenyl rotations

Tetracyclone, 2a, reacts with C(6)F(5)Li to yield 2-pentafluorophenyl-2,3,4,5-tetraphenylcyclopent-3-en-1-one, 7, and 5-hydroxy-5-pentafluorophenyl-1,2,3,4-tetraphenylcyclopentadiene, 8, as the result of 1,6 and 1,2 additions, respectively. In contrast, treatment of 3-ferrocenyl-2,4,5-triphenylcyclopentadienone, 2b, with lithiopentafluorobenzene leads to 4-ferrocenyl-4-pentafluorophenyl-2, 3,5-triphenylcyclopent-2-en-1-one, 9, and 5-hydroxy-5-pentafluorophenyl-2-ferrocenyl-1,3, 4-triphenylcyclopentadiene, 10, the products of 1,4 and 1,2 addition, respectively. The structures of 7-9 have been established by X-ray crystallography, and the barriers to rotation (19-21 kcal mol(-)(1)) of the pentafluorophenyl groups in 8-10 have been studied by variable-temperature (19)F NMR. Nucleophilic attack at the ferrocenyl-bearing carbon in 2b is rationalized in terms of a zwitterionic structure in which the positive charge of the "cyclopentadienyl cation" is delocalized onto the iron atom in the organometallic substituent.     

Separation scheme for the determination of alkali metals (K, Rb, Cs), alkaline earths (Sr, Ba) and rare earths (Ce, Nd, Sm, Eu) in silicate materials by isotopic dilution analysis

A scheme is outlined for the separation of Li, K, Rb, Cs, Sr, Ba, Ce, Nd, Sm and Eu from silicate materials. The elements are separated by cation-exchange to provide groups suitable for mass spectrometric analysis, and are then further purified by anion-exchange. Results obtained by isotopic dilution analysis are reported for G-1, W-1, and the Harwell meteorite-in these measurements the alkali metals were determined separately from the other elements. Requirements are discussed for combining the procedures to form a more comprehensive method for use with a single sample.     

Observation of apigenin anionic clusters in the gas phase

The ubiquity and favorable medicinal properties of flavonoids make essential the determination of flavonoid levels in various matrices. While developing a liquid chromatography/tandem mass spectrometry method for the analysis of the flavonoid, apigenin, anionic oligomers and nitrate- and chloride-bound clusters of this compound were observed. Tandem mass spectrometry of these oligomers and cluster ions showed the cleavage of apigenin molecules from the precursor. The observation of these cluster ions shows the possibility of post-column derivatization techniques to enhance specificity in analysis. Copyright 2000 John Wiley & Sons, Ltd.     

The synthesis, structure and ethene polymerisation catalysis of mono(salicylaldiminato) titanium and zirconium complexes

The silyl ethers 3-But-2-(OSiMe3)C6H3CH=NR (2a-e) have been prepared by deprotonation of the known iminophenols (1a-e) and treatment with SiClMe3 (a, R = C6H5; b, R = 2,6-Pri2C6H3; c, R = 2,4,6-Me3C6H2; d, R = 2-C6H5C6H4; e, R = C6F5). 2a-c react with TiCl4 in hydrocarbon solvents to give the binuclear complexes [Ti{3-But-2-(O)C6H3CH=N(R)}Cl(mu-Cl3)TiCl3] (3a-c). The pentafluorophenyl species 2e reacts with TiCl4 to give the known complex Ti{3-But-2-(O)C6H3CH=N(R)}2Cl2. The mononuclear five-coordinate complex, Ti{3-But-2-(O)C6H3CH=N(2,4,6-Me3C6H2)}Cl3 (4c), was isolated after repeated recrystallisation of 3c. Performing the dehalosilylation reaction in the presence of tetrahydrofuran yields the octahedral, mononuclear complexes Ti{3-But-2-(O)C6H3CH=N(R)}Cl3(THF) (5a-e). The reaction with ZrCl4(THF)2 proceeds similarly to give complexes Zr{3-But-2-(O)C6H3CH=N(R)}Cl3(THF) (6b-e). The crystal structures of 3b, 4c, 5a, 5c, 5e, 6b, 6d, 6e and the salicylaldehyde titanium complex Ti{3-But-2-(O)C6H3CH=O}Cl3(THF) (7) have been determined. Activation of complexes 5a-e and 6b-e with MAO in an ethene saturated toluene solution gives polyethylene with at best high activity depending on the imine substituent.     

Does alpha-fluorination affect the structural trans-influence and kinetic trans-effect of an alkyl ligand? Molecular structures of Pd(TMEDA)(CH(3))(R(F)) and a kinetic study of the trans to cis isomerization of Pt(TMEDA)(CH(3))(2)I(R(F)) [R(F) = CF(2)CF(3), CFHCF(3), CH(2)CF(3)

Reaction of Pd(TMEDA)(CH(3))(2) [TMEDA = tetramethylethylenediamine] with fluoroalkyl iodides R(F)I affords a series of square planar Pd(II) complexes Pd(TMEDA)(CH(3))(R(F)) [R(F) = CF(2)CF(3) (9), CFHCF(3) (10), CH(2)CF(3) (11)], presumably by oxidative addition followed by reductive elimination of CH(3)I. The solid-state structures of each compound have been determined by single crystal X-ray diffraction studies, allowing the effect of increasing alpha-fluorination on the structural trans-influence of alkyl ligands to be examined. In these compounds there is no significant difference observed in the trans-influence of the three fluorinated alkyl ligands toward the trans-N atom, although a significant cis-influence on the neighboring methyl ligand is apparent. Oxidative addition of the same series of fluoroalkyl ligands to the corresponding Pt(TMEDA)(CH(3))(2) affords octahedral Pt(IV) complexes trans-Pt(TMEDA)(CH(3))(2)(R(F))I [R(F) = CF(2)CF(3) (12), CFHCF(3) (13), CH(2)CF(3) (14)] as the kinetic products. In each case, subsequent isomerization to the corresponding all cis-isomers is observed; in the case of 13, the stereocenter at the alpha-carbon results in two diastereomeric cis-isomers, which are formed at different rates. The molecular structures of 13 and its more stable all cis-isomer 16b have been crystallographically determined. Kinetic studies of the trans-cis isomerization reactions show the mechanism to involve a polar transition state, presumably involving iodide dissociation, followed by rearrangement of the cation, and iodide recombination. High dielectric solvents increase the rate, but solvent coordinating ability has no effect. Dissolved salts (LiI, LiOTf) show normal accelerative salt effects, with no inhibition in the case of added iodide, consistent with the formation of an intimate ion pair intermediate. The kinetic parameters show that the trans-effects of fluoroalkyl ligands in these compounds follow the order expected from the relative sigma-donor properties of the ligands, with CF(2)CF(3) < CFHCF(3) < CH(2)CF(3).