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541.
Kilian M. Krebs Jessica Wiederkehr Julia Schneider Dr. Hartmut Schubert Dr. Klaus Eichele Prof. Dr. Lars Wesemann 《Angewandte Chemie (International ed. in English)》2015,54(18):5502-5506
We herein report the synthesis and characterization of a terphenyl‐substituted SnII allyl compound featuring an η3 coordination mode in solution and in the solid state. Two examples for the interesting reactivity of the allyl SnII molecule are presented: Reactions with terminal alkynes result in the formation of tricyclic compounds by C? C bond formation and the dimerization of two Sn moieties whereas the reaction with benzonitrile leads to a sixteen‐membered ring system through C? H activation. 相似文献
542.
Frederick C. James Dieter Krebs 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2)
Abstract The major product formed by the action of phosphorus pentasulphide on 2 ethoxallyl 4,4 diethoxybutyronitrile has been shown to be 3 ethoxycarbonylthieno[2,3 c]isothiazole (1, R[dbnd]COOC2H5). 相似文献
543.
544.
Arno Lindemann Jrn Küper Christoph Jansen Joachim Kuchinke Christian Kster Adrienne Hammerschmidt Matthias Dch Timo Pruß Bernt Krebs 《无机化学与普通化学杂志》2001,627(3):419-425
The perseleno‐selenoborates Rb2B2Se7 and Cs3B3Se10 were prepared from the metal selenides, amorphous boron and selenium, the thallium perseleno‐selenoborates Tl2B2Se7 and Tl3B3Se10 directly from the elements in evacuated carbon coated silica tubes by solid state reactions at temperatures between 920 K and 950 K. All structures were refined from single crystal X‐ray diffraction data. The isotypic perseleno‐selenoborates Rb2B2Se7 and Tl2B2Se7 crystallize in the monoclinic space group I 2/a (No. 15) with lattice parameters a = 12.414(3) Å, b = 7.314(2) Å, c = 14.092(3) Å, β = 107.30(3)°, and Z = 4 for Rb2B2Se7 and a = 11.878(2) Å, b = 7.091(2) Å, c = 13.998(3) Å, β = 108.37(3)° with Z = 4 for Tl2B2Se7. The isotypic perseleno‐selenoborates Cs3B3Se10 and Tl3B3Se10 crystallize in the triclinic space group P1 (Cs3B3Se10: a = 7.583(2) Å, b = 8.464(2) Å, c = 15.276(3) Å, α = 107.03(3)°, β = 89.29(3)°, γ = 101.19(3)°, Z = 2, (non‐conventional setting); Tl3B3Se10: a = 7.099(2) Å, b = 8.072(2) Å, c = 14.545(3) Å, α = 105.24(3)°, β = 95.82(3)°, γ = 92.79(3)°, and Z = 2). All crystal structures contain polymeric anionic chains of composition ([B2Se7]2–)n or ([B3Se10]3–)n formed by spirocyclically fused non‐planar five‐membered B2Se3 rings and six‐membered B2Se4 rings in a molar ratio of 1 : 1 or 2 : 1, respectively. All boron atoms have tetrahedral coordination with corner‐sharing BSe4 tetrahedra additionally connected via Se–Se bridges. The cations are situated between three polymeric anionic chains leading to a nine‐fold coordination of the rubidium and thallium cations by selenium in M2B2Se7 (M = Rb, Tl). Coordination numbers of Cs+ (Tl+) in Cs3B3Se10 (Tl3B3Se10) are 12(11) and 11(9). 相似文献
545.
Our systematic studies on quaternary thioborates containing both a comparably small alkali metal ion and a large alkaline earth cation lead to the two new crystalline phases KBa4(BS3)3 and K4Ba11(BS3)8S. The former consists of isolated BS3 units and the corresponding counter‐ions while in the latter BS33– and S2– anions coexist. In both compounds boron is found in a trigonal‐planar coordination, in the case of K4Ba11(BS3)8S the additional sulfide anions are located inside an octahedron built of six barium cations. The two compounds were prepared in solid state reactions from the metal sulfides, amorphous boron and sulfur. Evacuated carbon coated silica tubes were used as reaction vessels since temperatures up to 870 K were applied. KBa4(BS3)3 crystallizes in the monoclinic space group C 2/c (no. 15) with a = 14.299(6) Å, b = 8.808(3) Å, c = 13.656(5) Å, β = 98.72(4)°, and Z = 4, while for K4Ba11(BS3)8S the trigonal space group R 3 c (no. 167) was found with a = 18.146(3) Å, c = 25.980(7) Å, and Z = 6. X‐ray powder patterns are compared to calculated diffraction data obtained from single crystal X‐ray structure determination, in the case of K4Ba11(BS3)8S vibrational spectra were recorded. 相似文献
546.
Systematic studies on quaternary thio‐ and selenoborates containing heavier alkaline earth metal cations led to the two new isotypic crystalline phases Sr4.2Ba2.8(BS3)4S and Ba7(BSe3)4Se. Both compounds consist of trigonal‐planar BQ3 (Q = S, Se) units, isolated Q2– anions and the corresponding counter‐ions. The two new chalcogenoborates were prepared in solid state reactions from the metal sulfides (selenides), amorphous boron and sulfur (selenium). Evacuated carbon coated silica tubes were used as reaction vessels since temperatures up to 870 K were applied. Sr4.2Ba2.8(BS3)4S and Ba7(BSe3)4Se crystallize in the monoclinic space group C2/c (no. 15) with a = 9.902(3) Å, b = 23.504(9) Å, c = 9.884(3) Å, β = 90.01(3)° and Z = 4 in the case of the thioborate, while for the selenoborate the lattice parameters a = 10.513(2) Å, b = 25.021(5) Å, c = 10.513(2) Å, β = 90.10(3)° were determined. X‐ray powder patterns are compared to calculated diffraction data obtained from single crystal X‐ray structure determination. 相似文献
547.
Ina Puscasu Christian Mock Michael Rauterkus Axel Rndigs Gesche Tallen Suman Gangopadhyay Johannes E. A. Wolff Bernt Krebs 《无机化学与普通化学杂志》2001,627(6):1292-1298
The reactions of [Pt(dpma)(H2O)2]2+ (dpma = 2,2′‐dipyridylmethylamine) and [Pt(dpk)(H2O)2]2+ (dpk = 2,2′‐dipyridylketone) with the model nucleobases 1‐methylthymine (1‐MeT) and 1‐methyluracil (1‐MeU) were studied. Reaction products were characterized by 195Pt NMR spectroscopy and by X‐ray structure analysis. The symmetric dpma and dpk diaqua complexes form dinuclear complexes with 1‐methylthymine, acting as secondary bridging ligand via its N3 and O4 donor atoms. [Pt2(dpma)2(1‐MeT)2](ClO4)2 · H2O ( 5 ) and [Pt2(dpk)(dpk · H2O)(1‐MeT)2](PF6)2 · 4 H2O ( 6 ) both show a head‐to‐head arrangement. Biological tests show a significant in vitro antitumor activity of [Pt(dpk)Cl2] against the human glioma cell line U 87. 相似文献
548.
Systematic studies on selenoborates containing a B12 cluster entity and alkali metal cations led to the new crystalline phase Na6[B18Se17] which consists of a icosahedral B12 cluster completely saturated with trigonal‐planar BSe3 units and sodium counter‐ions. Neighbouring cluster entities are connected in one direction via exocyclic selenium atoms forming the infinite chain anion ([B18Se16Se2/2]6–)∞. The new chalcogenoborate was prepared in a solid state reaction from sodium selenide, amorphous boron and selenium in evacuated carbon coated silica tubes at a temperature of 850 °C. Na6[B18Se17] crystallizes in the monoclinic space group C2/c (no. 15) with a = 18.005(4) Å, b = 16.549(3) Å, c = 11.245(2) Å, β = 91.35(3)° and Z = 4. 相似文献
549.
Stefanie Lamberth Holger Schmid Martin Muenchbach Thomas Vorherr Joachim Krebs Ernesto Carafoli Christian Griesinger 《Helvetica chimica acta》2000,83(9):2141-2152
Phospholamban (PLN), an amphipathic intrinsic membrane protein of 52 amino acids, is the modulator of the Ca2+ pump of cardiac, slow‐twitch, and smooth‐muscle sarcoplasmic reticulum. In response to β‐adrenergic stimulation, it becomes phosphorylated at Ser16 and/or Thr17, and dissociates from the pump, which, in turn, achieves its full activity. Here we present the three‐dimensional structure of chemically synthesized, monomeric PLN in an organic solvent. Monomerization (PLN normally forms homopentamers) was obtained by replacing Cys41 with phenylalanine (Phe=F), a modification that did not affect biological activity. The structure was determined by high‐resolution NMR in CHCl3/MeOH of the unphosphorylated state of [F41]PLN (C41F). Of the hydrophilic cytoplasmic parts IA (Met1 to Pro21) and IB (Gln22 to Asn30) and the membrane‐spanning hydrophobic domain II (Leu31 to Leu52) of PLN, domain IA, which contains the two phosphorylation sites Ser16 and Thr17, and domain II have been suggested to be helical and connected through the less‐structured hinge‐region IB. In the structural study presented here, [F41]PLN is composed of two α‐helical regions connected by a β‐turn (type III). The residues of the β‐turn (type III) are Thr17, Ile18, Glu19, and Met20, the first being one of the two phosphorylation sites (Ser16 and Thr17). The hinge region is located at the C‐terminal end of domain IA, and domain IB is part of a second helix. The two α‐helices comprising amino acids 4 – 16 and 21 – 49 are well‐defined (the root‐mean‐square deviations for the backbone atoms, calculated for a family of the structures, are 0.58 and 0.92 Å, resp.). Pro21 is at the beginning of the C‐terminal helix and in the trans conformation. 相似文献
550.