Two-Dimensional Model Networks

This article is concerned with the structure and dynamic properties of thin films that have been chemically stabilized by polymerization and cross-linking reactions. By using different types of monomers it is possible to construct networks with rubber-like elasticity or with glassy properties, or temporary networks, in the interfacial region between oil and water. The systematic study of these ultrathin membrances offers new insights into aspects of current research, and opens up a wide range of potential new applications.     

Mecanisme d'hydratation des niobates alcalins lamellaires de formule A4Nb4O17 (A = K,Rb, Cs)

Two double oxides, K₄Nb₆O₁₇ and K₂Rb₂Nb₆O₁₇ · 5H₂O, have been synthesized as single crystals. Unit cell dimensions are a = 7.83, b = 33.21, c = 6.46 Å for the first and a = 7.84, b = 41.75, c = 6.50 Å for the second. The common space group is P2₁nb (Z = 4). The K₄Nb₆O₁₇ structure was solved by X-ray diffraction using three-dimensional Patterson and Fourier techniques with 1401 reflections collected on films. Comparison between the structure types of K₄Nb₆O₁₇ and Rb₄Nb₆O₁₇ · 3H₂O leads to elaboration of a pattern for the pentahydrate which was confirmed by the crystal structure. These results show that the hydration mechanism leads only to compounds with three or five molecules of water and they explain the differences of stability found between several compounds of the same type.     

The birch reduction of thiophine-2-carboxylic acid

The Birch reduction of thiophene-2-carboxylic acid was investigated. The course of the reaction was controlled by altering the ratio of lithium to acid and by changing the proton source.     

The first uranyl-methine carbon bond; a complex with out-of-plane uranyl equatorial coordination

Treatment of [UO2Cl2(thf)3] in thf with one equivalent of [Na(CH(Ph2P = NSiMe3)2)] yields an unusual uranyl chloro-bridged dimer containing a uranium(VI)-carbon bond as part of a tridentate bis(iminophosphorano)methanide chelate complex. The methine carbon is displaced significantly from the uranyl equatorial plane.     

Octanuclear cobalt and nickel cages featuring formate ligands

Two new octanuclear cages are reported which feature formate as a bridging carboxylate which has been formed in situ from decomposition of triphenylacetate used as a ligand.     

The conversion of a pyrrole trimer derivative into a 4,5,6,7‐tetra­hydro‐4‐­(pyrrol‐2‐yl)indol‐7‐yl­tosyl­aminoindole

Vilsmeier formyl­ation of trans‐1‐(4‐methyl­phenyl­sulfonyl)‐2,5‐bis(pyrrol‐2‐yl)­pyrrolidine leads to cleavage of the central ring then a reclosure resulting in the formation of trans‐N‐[2‐formyl‐4‐(5‐formyl­pyrrol‐2‐yl)‐4,5,6,7‐tetra­hydro­indol‐7‐yl]­toluene­sulfon­amide, C₂₁H₂₁N₃O₄S.     

4‐Methyl‐N‐[2‐(p‐tolylsulfanyl)phenyl]benzene­sulfonamide

The title compound, C₂₀H₁₉NO₂S₂, is formed by a palladium–copper‐catalyzed reaction between 4‐methyl‐N‐[2‐(prop‐2‐ynyl­sul­fanyl)­phenyl]­benzene­sul­fon­amide and p‐iodo­toluene. The mol­ecules contain three essentially planar parts, namely an amino­thio­phenol moiety (A), a toluene­sulfone moiety excluding the oxo ligands (B) and a tolyl group (C), approximately orthogonal to each other; the dihedral angles A/B, A/C and B/C are 111.6 (1), 89.3 (1) and 101.4 (1)°, respectively. Intermolecular N—H?O hydrogen bonds link the mol­ecules into infinite one‐dimensional chains.     

Isothiourea‐Mediated Asymmetric O‐ to C‐Carboxyl Transfer of Oxazolyl Carbonates: Structure–Selectivity Profiles and Mechanistic Studies

The structural motif within a series of tetrahydropyrimidine‐based isothioureas necessary for generating high asymmetric induction in the asymmetric Steglich rearrangement of oxazolyl carbonates is fully explored, with crossover and dynamic ¹⁹F NMR experiments used to develop a mechanistic understanding of this transformation.