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951.
Y Xiang NV Izarova F Schinle O Hampe B Keita U Kortz 《Chemical communications (Cambridge, England)》2012,48(79):9849-9851
The discrete heteropolyaurate [Au(III)(4)O(4)(Se(IV)O(3))(4)](4-) () represents only the second member of this class ever reported, and was synthesized via one-pot room temperature condensation in aqueous medium. was structurally characterized in the solid state and in solution by single-crystal XRD, TGA, FT-IR, (77)Se NMR, mass spectrometry and electrochemistry. 相似文献
952.
F Kniep L Rout SM Walter HK Bensch SH Jungbauer E Herdtweck SM Huber 《Chemical communications (Cambridge, England)》2012,48(74):9299-9301
Bi- and tridentate polycationic halogen bond donors based on 5-iodo-1,2,3-triazolium groups have been synthesized by 1,3-dipolar cycloaddition reactions. These halogen-based Lewis acids have been evaluated as activators in a halide-abstraction benchmark reaction. 相似文献
953.
Afanasiev P Kudrik EV Albrieux F Briois V Koifman OI Sorokin AB 《Chemical communications (Cambridge, England)》2012,48(49):6088-6090
The first high-valent iron oxo complex on the phthalocyanine platform has been prepared from iron tetra-tert-butyl-phthalocyanine and m-chloroperbenzoic acid and characterized by low temperature UV-vis, cryospray MS, EPR, X-ray absorption and high resolution X-ray emission methods. 相似文献
954.
A modular and highly stereoselective synthesis of the title compound was developed. Key steps in the assembly of the carbon framework of ripostatin?B (1; see scheme) were a stereoselective Paterson aldol reaction and a high-yielding ring-closing metathesis mediated by Grubbs first generation catalyst. The C15 hydroxy group was established through Tishchenko-Evans reduction in excellent yield and selectivity. 相似文献
955.
Oldach F Al Toma R Kuthning A Caetano T Mendo S Budisa N Süssmuth RD 《Angewandte Chemie (International ed. in English)》2012,51(2):415-418
Expanded repetoire: Synthetic amino acids translated into propeptides dramatically increase the chemical diversity of the two-component lantibiotic lichenicidin. This opens new routes towards novel and unique peptide antibiotic sequences, which could display features important for medical applications. 相似文献
956.
Dr. Christina Tönshoff Matthias Müller Prof. Dr. Tapas Kar Florian Latteyer Prof. Dr. Thomas Chassé Dr. Klaus Eichele Prof. Dr. Holger F. Bettinger 《Chemphyschem》2012,13(5):1173-1181
The doping of graphene molecules by borazine (B3N3) units may modify the electronic properties favorably. Therefore, the influence of the substitution of the central benzene ring of hexa‐peri‐hexabenzocoronene (HBC, C42H18) by an isoelectronic B3N3 ring resulting in C36B3N3H18 (B3N3HBC) is investigated by computational methods. For comparison, the isoelectronic and isosteric all‐B/N molecule B21N21H18 (termed BN) and its carbon derivative C6B18N18H18 (C6BN), obtained by substitution of a central B3N3 by a C6 ring, are also studied. The substitution of C6 in the HBC molecule by a B3N3 unit results in a significant change of the computed IR vibrational spectrum between 1400 and 1600 cm?1 due to the polarity of the borazine core. The properties of the BN molecule resemble those of hexagonal boron nitride, and substitution of the central B3N3 ring by C6 changes the computed IR vibrational spectrum only slightly. The allowed transitions to excited states associated with large oscillator strengths shift to higher energy upon going from HBC to B3N3HBC, but to lower energy upon going from BN to C6BN. The possibility of synthesis of B3N3HBC from hexaphenylborazine (HPB) using the Scholl reaction (CuCl2/AlCl3 in CS2) is investigated. Rather than the desired B3N3HBC an insoluble and X‐ray amorphous polymer P is obtained. Its analysis by IR and 11B magic angle spinning NMR spectroscopy reveals the presence of borazine units. The changes in the 11B quadrupolar coupling constant CQ, asymmetry parameter η, and isotropic chemical shift δiso(11B) with respect to HPB are in agreement with a structural model that includes B3N3HBC‐derived monomeric units in polymer P. This indicates that both intra‐ and intermolecular cyclodehydrogenation reactions take place during the Scholl reaction of HPB. 相似文献
957.
958.
Electrodeposition of tin and tin alloys from electrolytes containing tin(II) and pyrophosphates is an important process in metal finishing, but the nature of the tin pyrophosphate complexes present in these solutions in various pH regions has remained unknown. Through solubility and pH studies, IR and (31)P and (119)Sn NMR spectroscopic investigations of solutions obtained by dissolving Sn(2)P(2)O(7) in equimolar quantities of either Na(4)P(2)O(7)·10H(2)O or K(4)P(2)O(7) the formation of anionic 1:1 complexes {[Sn(P(2)O(7))]}(n)(2n-) has now been verified and the molecular structures of the monomer (n = 1) and the dimer (n = 2) have been calculated by density functional theory (DFT) methods. Whereas the alkali pyrophosphates Na/K(4)P(2)O(7) give strongly alkaline aqueous solutions (pH ~13), because of partial protonation of the [P(2)O(7)](4-) anion, the [Sn(P(2)O(7))](2-) anion is not protonated and the solutions of Na/K(2)[Sn(P(2)O(7))] are almost neutral (pH ~8). The monomeric dianion appears to have a ground state with C(2v) symmetry with the Sn atom in a square pyramidal coordination and the lone pair of electrons in the apical position, while the dimer approaches C(2) symmetry with the Sn atoms in a rhombic pyramidal coordination, also with a sterically active lone pair. A comparison of experimental and calculated IR details favors the monomer as the most abundant species in solution. With an excess of pyrophosphate, 3:2 and 2:1 complexes (P(2)O(7)):(Sn) are first formed, which, in the presence of more pyrophosphate, undergo rapid ligand exchange on the NMR time scale. The structure of the 2:1 complex [Sn(P(2)O(7))(2)](6-) was calculated to have a pyramidal complexation by two 1,5-chelating pyrophosphate ligands. Neutralization of these alkaline solutions by sulfuric or sulfonic acids (H(2)SO(4), MeSO(3)H), as also practiced in electroplating, appears to afford the tin(II) hydrogen pyrophosphates [Sn(P(2)O(7)H)](-) and [Sn(H(2)P(2)O(7))](0). The molecular structures of the mononuclear model units have also been calculated and were shown to have an unsymmetrical complexation and to feature trigonal pyramidal (pseudotetrahedral) coordination. NMR observations have shown that, contrary to the results obtained for Sn(II) compounds, Sn(IV) as present in K(2)SnO(3) or its hydrated form (K(2)Sn(OH)(6)) does not form a pyrophosphate complex in aqueous solution near pH 7. There is also no interference of sulfite. 相似文献
959.
We study the dynamics of semiflexible dendritic polymers following the method of Dolgushev and Blumen [J. Chem. Phys. 131, 044905 (2009)]. The scheme allows to formulate in analytical form the corresponding Langevin equations. We determine the eigenvalues by first block-diagonalizing the problem, which allows to treat even very large dendritic objects. A basic ingredient of the procedure is the observation that a set of eigenmodes in the semiflexible case is similar to that chosen by Cai and Chen [Macromolecules 30, 5104 (1997)] for fully flexible dendritic structures. Varying the flexibility of the macromolecules allows us to better understand their mechanical loss moduli G"(ω) based on their eigenvalue spectra. We present the G"(ω) for a series of stiffness parameters and for different functionalities of the branching points. 相似文献
960.
Daniels DP Deacon GB Harakat D Jaroschik F Junk PC 《Dalton transactions (Cambridge, England : 2003)》2012,41(1):267-277
A series of alkaline earth metallocene complexes carrying the diphenylphosphanocyclopentadienyl ligand, [Ae(L)(x)(η(5)-C(5)H(4)PPh(2))(2)] (Ae = Ca, L = thf, x = 1 (6a); Ae = Ca, L = dme, x = 1 (6b); Ae = Sr, L = thf, x = 1 (7); Ae = Ba, L = thf, x = 1 (8a); Ae = Ba, L = dme, x = 2 (8b)), were prepared by redox transmetallation/protolysis from the free metals, diphenylmercury and diphenylphosphanocyclopentadiene. These complexes were characterised using multinuclear NMR spectroscopy and two by single crystal X-ray diffraction. [Ca(dme)(η(5)-C(5)H(4)PPh(2))(2)] (6b) is a discrete neutral monomeric eight coordinate molecule in which the phosphorus atoms are not coordinated to the calcium ion and the larger barium analogue, ten-coordinate [Ba(dme)(2)(η(5)-C(5)H(4)PPh(2))(2)] (8b), has an extremely bent sandwich structure due to the two dme ligands attached to the metal. Bimetallic complexes, [Ae(thf)(x)(η(5)-C(5)H(4)PPh(2))(2)Pt(Me)(2)].(solv) (Ae = Ca, L = thf, x = 2, solv = 1.5thf (9); Ae = Sr, L = thf, x = 3, solv = 1.5thf (10); Ae = Ba, L = thf, x = 3, solv = thf (11)) were obtained by reaction of the homometallic complexes with [Pt(cod)(Me)(2)]. The crystal structures of [Ca(thf)(2)(η(5)-C(5)H(4)PPh(2))(2)Pt(Me)(2)].1.5thf (9), [Sr(thf)(3)(η(5)-C(5)H(4)PPh(2))(2)Pt(Me)(2)].1.5thf (10) and [Ba(thf)(3)(η(5)-C(5)H(4)PPh(2))(2)Pt(Me)(2)].thf (11) show the eight (calcium) and nine coordinate (strontium and barium) fragments acting as a chelating metalloligand attached to the square planar platinum through the phosphorus donor atoms. The solution chemistry of these bimetallic complexes has been investigated by NMR spectroscopy, electro-spray ionisation mass spectrometry and conductivity experiments which indicate that the bimetallic compounds persist in solution. 相似文献