Formation and properties of n-alkylammonium complexes with layered tri- and tetra-titanates

The formation of n-alkylammonium complexes was studied using Na₂Ti₃O₇ and K₂Ti₄O₉ and the results for both compounds were compared. Alkylammonium complexes could be obtained from H₂Ti₃O₇ and H₂Ti₄O₉·H₂O, which were prepared by HCl treatment of Na₂Ti₃O₇ and K₂Ti₄O₉ respectivel The complexes were formed by exchange of H⁺ with alkylammonium ions. Molecular intercalation of alkylamine was also possible with H₂Ti₄O₉·H₂O. However, alkylammonium complexes were not formed directly from Na₂Ti₃O₇ and from K₂Ti₄O₉. Orientations of alkylammonium ions in the interlayer are also discussed in relation to the structure of the titanate layers.     

The matrix effect on stereoselectivity of olefin cyclopropanation by arylcarbene

Temperature studies of additon of phenylcarbene to styrene showed that stereoselectivity changed rather dramatically as the reaction phase changed.     

Giant Nernst effect in CeCoIn5

We present a study of Nernst and Seebeck coefficients of the heavy-fermion superconductor CeCoIn5. Below 18 K, concomitant with a field-dependent Seebeck coefficient, a large sublinear Nernst signal emerges with a magnitude drastically exceeding what is expected for a multiband Fermi-liquid metal. In the mixed state, in contrast with all other superconductors studied before, this signal overwhelms the one associated with the motion of superconducting vortices. The results point to a hitherto unknown source of transverse thermoelectricity in strongly interacting electrons.     

Carbonylation of Lithium Enolates of Esters and Amides with Carbon Monoxide and Selenium

Abstract

Lithium enolates of esters, amides, and an acylsilane undergo carbonylation with carbon monoxide with the aid of selenium under mild conditions to yield the corresponding selenol esters after trapping with alkyl iodides.     

Continued fractions for quadratic elements in formal power series

There exist certain quadratic elements α∈?((t ^?1)) over the rational function field ?(t) having nonperiodic continued fraction expansion, see W.M. Schmidt in (Acta Arith. 95(2):139–166, 2000). Hence we need a modification of Lagrange’s theorem with regard to function fields instead of number fields. In this paper, we introduce a class of continued fractions and describe Lagrange’s theorem as a conjecture related to quadratic elements over ?(t). We give some examples which support our conjecture.     

Two‐dimensional correlation gel permeation chromatography study of aggregate–aggregate interactions during acid‐catalyzed polymerization of triethoxysilyl‐terminated polystyrene

The three‐step polymerization of a well‐defined polymeric silane coupling agent, triethoxysilyl‐terminated polystyrene, catalyzed by acid (H₃PO₄), was traced as a function of the reaction time with gel permeation chromatography (GPC). Time‐resolved GPC traces collected during the polymerization process were then used to construct two‐dimensional (2D) correlation maps via generalized 2D correlation analysis. The results demonstrated that the synchronous and asynchronous 2D correlation GPC spectra directly reflected the dynamic variation of aggregate–aggregate interactions during each step of the polymerization. In particular, it was found that the formation of aggregates among the cyclic trimers (or tetramers) and monomers was critical for the preferential production of pentamers in the reaction system. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3447–3460, 2004     

Selective oxidation of n-butane over Fe-promoted vanadyl pyrophosphate prepared from modification of nano-sized interlayer of lamellar vanadyl benzylphosphate

A novel approach for the preparation of promoted vanadyl pyrophosphate in well-defined structure was examined. Lamellar vanadyl benzylphosphate (LVBP) was used as a host material and iron acetylacetonate as a guest. It was found that iron acetylacetonate was successfully inserted into the interlayer of LVBP by heating of LVBP and iron acetylacetonate in toluene solution. Calcination of this in tercalated material resulted in a well-crystallized vanadyl pyrophosphate phase with uniform dispersion of Fe in bulk and surface. The obtained Fe-promoted vanadyl pyrophosphate showed an enhancement in the activity for selective oxidation of n-butane, especially at high temperature and long contact time.     

Preparation and properties of surface-active organocobalt complexes having long-chain alkyl groups

New types of surface-active organocobaltocenium(I) complexes, η-C_nH_2n+1X-C₅H₄(ηC₅H₅)₂Co⁺Y^? and(η-C_nH_2n+1X-C₅H₄)Co⁺Y^? (n = 6–16; X not present, NHCO or OCO; Y = Cl or PF₆) were prepared and their surface character studied. (1) The critical micelle concentrations of the cobaltocenium chlorides were much lower than those of corresponding trimethylammonium-type cationic surfactants. (2) The surface-active character of the cobaltocenium chlorides in aqueous solution (and the redox potentials of the hexafluorophosphates in acetonitrile) were affected by the substituents (X) in the cyclopentadienyl groups. (3) The surface activities of the cobaltocenium salts were lost on reduction with NaBH₄ to afford (alkyl-substituted cyclopentadiene) cyclopentadienylcobalt (0) complexes which were surface-inactive but could be re-oxidized to afford the surface-active cobaltoceium(I) salts. The cobalt complexes mentioned above may be the first examples of redoxresponsive surfactants.