Catalytic arylation of carbon-carbon double bond followed by N- or O-cyclization

Under the catalytic action of palladium,o-hydroxy- oro-amino-substituted aryl iodides oxidatively add to palladium(0), insert strained or rigid olefins, and close the ring between the aliphatic carbon and theortho-functional group. This reaction occurs under mild conditions in the absence of phosphine ligands in a DMF solution and affords fused dihydrofurans or-pyrroles.     

Manganese(III) Formate: A Three-Dimensional Framework That Traps Carbon Dioxide Molecules

Carbon dioxide, formic acid, and water molecules are trapped in the crystal lattice of manganese(III ) formate (see 1 ), which was obtained by reducing permanganate with formic acid. Each CO₂ guest molecule exhibits four C−H⋅⋅⋅O−C−O interactions with the three-dimensional host framework of Mn(HCOO)₃ units. Compound 1 undergoes an antiferromagnetic phase transition at 27 K.     

Dynamic Electrical-Mechanical Energy Coupling in Electrolyte-Mineral Systems

Electrical-mechanical and mechanical-electrical coupling phenomena have been observed in geo-materials. Underlying internal phenomena are not always clear. In this paper, we identify potential microscale processes on the bases of previously published research; fundamental physical principles and analytical models are included. Second, we notice important inconsistencies between theoretically predicted values or high-frequency laboratory data with respect to low-frequency field observations. To explore these differences, we conduct a laboratory experimental study that simulates field conditions, placing emphasis on low frequency coupling, that is, less than 10 kHz. Both, mechanical-electrical and electrical-mechanical effects are observed. Finally, hypotheses are presented in an attempt to explain observed differences.     

The first structurally characterized aluminum compound with two SH groups: [LAl(SH)(2)] (L = N(Ar)C(Me)CHC(Me)N(Ar), Ar = 2,6-i-Pr(2)C(6)H(3)) and the catalytic properties of the sulfur P(NMe(2))(3) system

Surprisingly stable is the bis(hydrogen sulfide) of aluminum LAl(SH)(2) with two terminal arranged SH groups. The insertion of sulfur into the Al-H bonds is catalyzed by SP(NMe(2))(3). A possible mechanism is discussed.     

Hydrogen-induced surface metallization of beta-SiC(100)-(3x2) revisited by density functional theory calculations

Recent experiments on the silicon terminated (3 x 2)-SiC(100) surface indicated an unexpected metallic character upon hydrogen adsorption. This effect was attributed to the bonding of hydrogen to a row of Si atoms and to the stabilization of a neighboring dangling bond row. Here, on the basis of density-functional calculations, we show that multiple-layer adsorption of H at the reconstructed surface is compatible with a different geometry: in addition to saturating the topmost Si dangling bonds, H atoms are adsorbed at rather unusual sites, i.e., stable bridge positions above third-layer Si dimers. The results thus suggest an alternative interpretation for the electronic structure of the metallic surface.     

A new catalytic synthesis of non-conjugated alkenynes

A new synthesis of alk-1-en-4-ynes catalyzed by nickel(0) complexes under mild conditions is described. The catalyst appers to be particularly sensitive to ligands; and to their ability to undergo dissociation from the metal.     

Bonding Capabilities of the Biochemical Buffer TRIS toward Copper(II) Ion. Structure and Magnetic Properties of Binuclear and Tetranuclear Systems

Following X-ray crystal structure studies, the products of the reaction between Cu(II) halides and tris(hydroxymethyl)methylamine (TRIS) can be formulated as [Cu(TRISH_?1)(TRIS)]₂X₂ and [Cu(TRISH_?1)X]₄ (X ? Cl, Br). TRISH_?1 is the deprotonated ligand. Initial metal-ligand stoichiometric ratios of 1:2 and 1:1 are required to obtain the former and the latter species, respectively. Relevant crystal data for the dimeric compound with X ? Br are: monoclinic, a = 11.39(2), b = 10.049(2), c = 12.149(2) Å, β = 95.83(2)°, space group P2₁/c, Z = 2. The tetramer with X ? Cl crystallizes in teh triclinic space group P 1 with a 9.182(1), b = 9.120(2), c = 8.817(1) Å, α = 88.95(1), β = 87.01(1), γ = 84.13(1), Z = 1. In the dimer, two square planar Cu(II)-units are held together by two H-bonds of the type O? H …? O, which involve the O-atoms coordinated to the metals. The formation of an eight-membered cycle containing two metal ons ensues. The tetramer contains two dinuclear units formed by two metal centers, square planar in first approximation, which share one edge; the arrangement is significantly puckered at this vector. One of these bridging O-atoms has μ₃ character as it serves as a weak apical donor for a Cu-atom of another binuclear unit. Thus a step-like geometry of the central core is obtained. Both compounds have constant magnetic moments at least down to the liquid N₂ temperature. In this respect, they differ from other complexes of Cu(II) having comparable geometries, but temperature-dependent magnetic moments.