Publications

Aus raumzentrierten Ge9-Parallelepipeden ist [Ge9O18(OH)4]⋅2 H2ppz⋅0.5 H2O (ASU-14; ppz = Piperazin) aufgebaut. Bei diesem für ein Germanat mit einem offenen Gerüst neuen Strukturtyp (Ausschnitt siehe Bild) sind die Baueinheiten an jeder der acht Ecken so miteinander verbunden, daß sich die seltene Polycuban-Topologie mit einem Kanalsystem aus zehn- und achtgliedrigen Ringen (Porengröße 5×6 bzw. 4×4 Å2) ergibt, in dem sich Piperaziniumkationen und Wassermoleküle befinden.

This is the AmeriFlux version of the carbon flux data for the site US-Tw4 Twitchell East End Wetland. Site Description - The Twitchell East End Wetland is a newly constructed restored wetland on Twitchell Island, CA. This site and the surrounding region are part of the San Joaquin - Sacramento River Delta drained beginning in the 1850's and subsequently used for agriculture. The site was previously a corn field. The wetland was designed to have a mix of vegetated and open water channels and ponds (due to surface elevation differences). Flooding of the wetland was done gradually beginning in January, 2014. Berms wind throughout the wetland to allow vehicle access. Tule and Cattail plant material from a nearby wetland were spread along the berms immediately prior to flooding to facilitate plant establishment and stabilization of the berms from wind/water erosion. The tower was installed on November 25, 2013.

A general continuum model has recently been proposed for the dynamics of ion intercalation in a single crystal of rechargeable-battery electrode materials [1]. When applied to strongly phase-separating, highly anisotropic materials such as LiFePO4, phase-transformation waves are predicted between the lithiated and unlithiated portions of a crystal. In this paper, we extend the analysis of the wave dynamics, and we describe a new mechanism for current capacity fade through the interactions of these waves with defects in the material.

Lignocellulosic biomass is an attractive resource for producing transportation fuels, and consequently novel approaches are being sought for transforming the lignin and cellulosic constituents of biomass to fuels or fuel additives. Glucose, the monomer of cellulose, is a good starting material for exploring such chemistries. We report here the results of an investigation aimed at identifying catalysts for the dehydration of glucose to 5-hydroxymethylfurfural (HMF) dissolved in ionic liquids and the subsequent conversion of HMF to 2,5-dimethylfuran (DMF), a high-energy content product that could be used as a fuel or fuel additive. Heteropoly acids were found to be exceptionally active and selective catalysts for the dehydration of glucose. Nearly 100% yield of HMF could be achieved using 12-molybdophosphoric acid (12-MPA) in a solution of 1-ethyl-3-methylimidazolium chloride (EMIMCl) and acetonitrile. The addition of acetonitrile to EMIMCl suppressed the formation of humins from glucose. The high HMF selectivity achievable with heteropoly acid catalysts is ascribed to stabilization of 1,2-enediol and other intermediates involved in the dehydration of glucose and the avoidance of forming the 2,3-enediol intermediate leading to furylhydroxymethyl ketone (FHMK). Carbon-supported metals, and in particular Pd/C, were effective in promoting the hydrogenation of HMF dissolved in EMIMCl and acetonitrile to DMF. The following intermediates were observed in the hydrogenation of HMF to DMF: 5-methylfurfural (MF), 5-methylfurfyl alcohol (MFA), and 2,5-dihydroxymethylfuran (DHMF). The relative rate of formation and consumption of these compounds was explored by using each of them as a reactant in order to identify the reaction pathway from HMF to DMF. It was also observed that HMF produced via glucose dehydration could be converted to DMF without isolation, if the dehydration catalyst, 12 MPA, was replaced by the hydrogenation catalyst, Pd/C. This two-step catalytic approach provides the basis for completely converting glucose to HMF and further converting HMF to DMF.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Abstract not Available.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Transmetalation from boron to rhodium in the absence of basic activators is reported to proceed by β-aryl elimination from a series of triethylphospine-ligated rhodium(I) arylboronates and diarylborinates. [Rh(PEt3)3OB(OH)Ar] were prepared by treating {Rh(PEt3)2[N(SiMe3)2} with the corresponding arylboronic acid, ArB(OH)2, in the presence of added PEt3. One example of these complexes was characterized by X-ray diffraction. [Rh(PEt3)3OB(mesityl)2] and [Rh(PEt3)2OB(mesityl)2] were prepared by analogous methods from dimesitylborinic acid in the presence and absence of added PEt3. Heating of the trisphosphine boronate complexes in cyclohexane generated the rhodium aryl complexes, [(PEt3)3RhAr] and boroxin in good to high yields. [Rh(PEt3)3OB(mesityl)2] also underwent aryl migration to form [(PEt3)3Rh(mesityl)] and a cyclic boroxine. Kinetic studies showed that migration of more electron-poor aryl groups from the boronate complexes was slightly faster than migration of more electron-poor aryl groups and that migration of the o-anisyl group was particularly fast. Kinetic results are most consistent with a ligand dissociation pathway with a rate-limiting β-aryl elimination from a 14-electron, bis(phosphine) intermediate.