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Sorption of coinage metal cyano complexes by a chelating resin containing amino-glucitol groups
(1994)
Ligand Exchange Reactions of Bis(acetyl-acetonato)dioxomolybdenum(VI) and Molybdenum Hexacarbonyl
(1995)
Crystal structure of methoxo-oxo[benzoylaceton-salicyl hydrazonato(2-)]vanadium(V), C18H17N2O5V
(1996)
Selenides of the type R1Se-EMe3 (E = Si, Ge, Sn, Pb) react with xenon difluoride by cleavage of the Se-E bond to yield the R1Se-F intermediate and the fluorides Me3E-F, whereas the Se-C bond in PhSe-tBu (E = C) is stable against XeF2. The presence of R1Se-F intermediates is confirmed by addition to acetylenes (4-octyne, 3-hexyne). Thus, the fluoroselenenylation of acetylenes gives fluoro(organylseleno)olefins in preparative yields. In the cases of E = Si, Ge, Sn, and Pb, aryl and n-alkyl groups are suitable as the substituent R1. The X-ray crystal structural analysis of (E)-3- (p-carboxyphenylseleno)-4-fluorohex-3-ene - the first example of an uncharged fluoroselenoolefin synthesized from p- EtO2C-C6H4-Se-SnMe3, XeF2, and 3-hexyne followed by an ester hydrolysis - shows that the addition of the selenenylfluoride intermediate to the acetylene proceeds via a trans-addition, as is known for the R2Se2-XeF2 reagents.
Core-Modified Hexaphyrins; Characterization of Two- and Four-Ring Inverted 26 ô Aromatic Macrocycles
(2003)
Two different approaches. with an unsaturated carbohydrate as a radical acceptor and a carbohydrate derived aldehyde as a radical precursor, led to key intermediates in the synthesis of 3-deoxy-D-oct-2-ulosonic acids (KDO). Manganese(III) acetate and cerium(IV) ammonium nitrate were the reagents of choice for the oxidative generation of radicals, whereas samarium(II) iodide was employed for reductive couplings. Both strategies were realized by using easily available starting materials, with acetic acid as C-2 and ethyl acrylate as C-3 building blocks, respectively
Heterobimetallic 3d-4-complexes with bis(1;2-dithiooxalato)nickelate(II) as planar bridging block
(2005)
Planar bis(1,2-dithiooxalato)nickelates(II) react in aqueous solutions of lanthanide ions to form pentanuclear, heterobimetallic complexes of the general composition [{Ln(H2O)(n)}(2)- {Ni(dto)(2)}(3)] (.) xH(2)O (Ln = Y3+, La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+, Lu3+; n = 4 or 5; x = 9-12). With [{Nd(H2O)(5)}(2){Ni(S2C2O2)(2)}(3)] (.) xH(2)O (x = 10-12) (1) and [{Er(H2O)(4)}(2){Ni(S2C2O2)(2)}(3)] (.) xH(2)O (x = 9- 10) (2) we were able to isolate two complexes of this series as single crystals, which were characterized by X-ray structure analysis. Depending on the individual ionic radii of the lanthanide ions, the compounds crystallize in two different crystal systems with the following unit cell parameters: 1, monoclinic in P2(1)/c with a = 11.3987(13), b = 11.4878(8), c = 20.823(2)angstrom , beta = 98.907(9)degrees and Z = 2; 2, triclinic in P (1) over bar with a = 10.5091(6), b = 11.0604(6), c = 11.2823(6) angstrom, alpha = 107.899(4)degrees, beta = 91.436(4)degrees, gamma = 112.918(4)degrees and Z = 1. The channels and cavities appearing in the packing of the molecules are occupied by uncoordinated water molecules. High magnetic moments up to 14.65 BM./f.u. have been observed at room temperature due to the combined moments of the individual lanthanide ions
General syntheses have been developed for meso-substituted porphyrins with one or two substituents in the 5,10- positions and no beta substituents. 5-Substituted porphyrins with only one meso substituent are easily prepared by an acid-catalyzed condensation of dipyrromethane, pyrrole-2-carbaldehyde. and an appropriate aldehyde using a "[2+1+1]" approach. Similarly, 5,10-disubstituted porphyrins are accessible by simple condensation of unsubstituted tripyrrane with pyrrole and various aldehydes using a "[3+1]" approach. The yields for these reactions are low to moderate and additional formation of either di- or mono-substituted porphyrins due to scrambling of the intermediates is observed. However, the reactions can be performed quite easily and the desired target compounds are easily removed due to large differences in solubility. A complementary and more selective synthesis involves the use of organolithium reagents for SNAr reactions. Reaction of in situ generated porphyrin (porphine) with 1.1-8 equivalents of RLi gave the monosubstituted porphyrins, while reaction with 3-6 equivalents of RLi gave the 5,10-disubstituted porphyrins in yields ranging from 43 to 90%. These hitherto almost inaccessible compounds complete the series of different homologues of A-, 5,15-A(2)-, 5,10-A(2)-, A(3)-, and A(4)-type porphyrin's and allow an investigation of the gradual influence of type, number, and regiochemical arrangement of substituents on the properties of meso-substituted porphyrins. They also present important starting materials for the synthesis of ABCD porphyrins and are potential synthons for supramolecular materials requiring specific substituent orientations
The crystal and molecular structures of sodium and barium complexes of dibenzo-24-crown-8 ether
(2006)
The sodium and barium isothiocyanate complexes of 6,7,9,10,12,13,20,21,23,24,26,27-dodecahydrodibenzo[b,n]- 1,4,7,10,13,16,19,22-octaoxacyclotetracosin (dibenzo-24-crown-8 ether = DB24C8) were synthesized and analyzed by X-ray diffraction. The sodium complex, [Na(DB24C8)(NCS)(H2O)] 1, crystallizes in the orthorhombic space group Fdd2 with 16 molecules in the unit cell. The coordination number of Na is 6 and the central ion is located in a distorted octahedric environment. Only four of the crown ether oxygen atoms are involved. The coordination polyhedron is completed by the isothiocanate anion and by a water molecule, which is stabilized by hydrogen bonds. The barium complex, [Ba(DB24C8)(NCS)(2)] 2, crystallizes in the trigonale space group P3(1)21 with 3 molecules in the unit cell. Crystallographic C-2 symmetry is observed for the complex. The coordination number of Ba is 10. Barium is coordinated with the eight oxygen atoms of the macrocyclic ligand and with two isothiocyanate anions. The absolute structure was estimated using the FLACK parameter