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1.
Monoclinic (N2H6)3Zr2F13·F crystallizes in space group P21-C 2 2 (No. 4) with unit cell dimensionsa=5.670(1),b=10.984(2),c=10.601(2) Å,=93.88(1)°,V=658.7(4) Å3 andZ=2. Two different types of N2H6 2+ ions are present. One is involved in strong H-bonds to F ions in infinite chains running along the a axis (the shortest N-F distance is 2.437(5) Å), and the other links the structure through weaker bi- and trifurcated H-bonds to fluorine ligands of the Zr2F13 5– ions. The N-N bond lengths range from 1.430(5) to 1.446(5) Å with apparently no meaningful correlation to the type of N2H2 2+ ions. The Zr2F13 5– ions have very nearly C2 point symmetry and are formed by joining two distorted bicapped trigonal prisms of ZrF8-units through a common face. Distances of Zr-F terminal bonds range from 2.015(2) to 2.112(2) Å and of bridging bonds from 2.133(2) to 2.212(2) Å. (N2H6)3Hf2F13·F is isomorphous. The vibrational spectra of the two compounds are nearly identical, with the exception of a strong infrared band, which is assigned to a stretching mode with the moving central atom within the anion. The anion part of the spectrum is simple, showing broad unresolved bands. The cation part shows two types of N2H6 ions. H-Bonding is strongly present in the spectra, but no simple correlations with the H-bond strength is evident.  相似文献   
2.
In the title compound, C13H13N5O4·H2O (4,5′‐cyclo­wyosine·H2O), the cyclization forces a syn arrangement of the aglycon with respect to the sugar moiety. The ribo­furan­ose part of the mol­ecule displays a β‐d configuration with an envelope C1′‐endo pucker. The mol­ecules are arranged in columns along the short a axis and are linked to water mol­ecules through O—H?O and O—H?N hydrogen bonds.  相似文献   
3.
Trans-[Cr(NH3)4F2]I·H2O (A) has monoclinic P2l/m (No. 11) space group witha=5.033 (3),b=16.333 (10),c=5.539 (3) Å and =98.47 (3)°,Z=2.Cis-[Cr(NH3)4F2]ClO4 (B) has tetragonal space group I4lmd (No. 109) witha=7.417 (1),c=16.610 (2) Å,Z=4. Cr–F and Cr–N bonding distances are 1.894 (3); 2.087 and 2.083 (5) Å for A and 1.887 (6); 2.062 (5) and 2.051 (7) Å for B. Octahedral angles within the cations are close to 90° for both compounds. Cr–N bondtrans to Cr–F bond in thecis compound is shorter. Structures were refined toR 2 values of 0.072 (A) and 0.058 (B).Trans-[Cr(NH3)4F2]I·H2O has weak N–H–F hydrogen bonds between the cations. None such interactions were found incis-[Cr(NH3)4F2]ClO4.
Fluorhältige Komplexe des Cr(III), 2. Mitt.: Kristall- und Molekülstruktur von trans-[Cr(NH3)4F2]I·H2O und cis-[Cr(NH3)4F2]ClO4
Zusammenfassung Trans-[Cr(NH3)4F2]I·H2O (A) kristallisiert in der Raumgruppe P2l/m (No. 11) mitZ=2 unda=5,033 (3),b=16,333 (10),c=5,539 (3) Å und =98,47 (3)°.Cis-[Cr(NH3)4F2]ClO4 (B) kristallisiert in der Raumgruppe I4lmd (No. 109) mitZ=4,a=7,417 (1) undc=16,610 (2) Å. Die Cr–F- und Cr–N-Abstände sind 1,894 (3); 2,087 (6), 2,083 (5) Å für A und 1,887 (6); 2,062 (5), 2,051 (7) Å für B. Die octaedrischen Bindungswinkel innerhalb der Kationen weichen nicht viel von 90° ab. Der Cr–N-Abstand intrans-Position der Cr–F-Bindung ist kürzer. Die Strukturen wurden bis zu GütefaktorenR 2 0,072 (A) und 0,058 (B) verfeinert. Bei der Verbindung A wurden schwache N–H ... F-Wasserstoff-Bindungen zwischen verschiedenen Kationen beobachtet, während bei der Verbindung B keine Wasserstoff-Bindungen vorhanden sind.
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4.
The Iteraltive Extended Hückel Molecular Orbital method has been adapted to calculation of the properties of an electrode and compact layer. Predictions of the stablest orientations, on the Pt(111) surface of species such as H2O, Pt, OH?, H, and the halides, F?, Cl?, Br? and I?, based upon calculation of the total energy corresponding to various internuclear distances, are reported. The calculations correctly predict self-adsorption of Pt on the Pt(111) surface at the face-centered cubic closest-packing position. The H2O molecule is predicted to locate itself above three adjoining Pt atoms, with the O atom closest to the surface and the H atoms opposite the O. Similar results were obtained for OH? and the halides. Atomic H, however, is predicted to drop into the plane of centers of the Pt surface atoms, where it would lie between, three adjacent Pt atoms. Application of the method to electrode studies requires only modest amounts of computer time but produces surprisingly reliable qualitative predictions. Compulation of electrochemical quantities such as charge, differential capacitance, surface tension and potential energy as a function of electrode potential will be described in future work.  相似文献   
5.
We report that the cis/trans ratio of the proline peptide bond can be strongly influenced by the chirality of the acyl residue preceding proline. Acyl moieties derived from (2S)-2,6-dimethyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-2-carboxylic acid (8) and (2R)-3-methoxy-2-methyl-2-(4-methyl-2-nitrophenoxy)-3-oxopropanoic acid (5) in acyl-Pro molecules influence isomerization of the proline peptide bond constraining the omega dihedral angle to the trans orientation. Structures of benzyl (2S)-1-([(2S)-2,6-dimethyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-2-yl]carbonyl)-2-pyrrolidinecarboxylate (3) derived from 2D (1)H NMR conformational analysis and crystallographic data exhibit only the trans conformation of proline peptide bond. On the other hand the diastereomer 4, which contains an (R) acyl moiety, exhibits two sets of signals in (1)H NMR spectra. The signals were assigned to trans (72%) and cis (28%) conformers. Crystallographic analysis of 4 showed that only the cis conformation is present in the crystalline state. The (1)H NMR chemical shift pattern of three sets of signals observed in 2 was observed also in benzyl (2S)-1-[(2R/S)-3-methoxy-2-methyl-2-(4-methyl-2-nitrophenoxy)-3-oxopropanoyl]-2-pyrrolidinecarboxylate. (R)-Carboxylic acid 5, after coupling with (S)-ProOBn, yielded benzyl (2S)-1-[(2R)-3-methoxy-2-methyl-2-(4-methyl-2-nitrophenoxy)-3-oxopropanoyl]-2-pyrrolidinecarboxylate (6), which in DMSO-d(6) exhibited only the trans conformation of the proline peptide bond. These results suggest that in these particular cases acyl-Pro peptide bond isomerization is strongly influenced by the stereochemistry of the acyl residue preceding proline. (2S)-2,6-Dimethyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-2-carboxylic acid (8) and (2R)-3-methoxy-2-methyl-2-(4-methyl-2-nitrophenoxy)-3-oxopropanoic acid (5) are promising chiral peptidomimetic building blocks that can be used as acyl moieties to force the proline peptide bond into the trans conformation in a variety of acyl-Pro molecules.  相似文献   
6.
By the reaction of KCN with Cp2TiCl2 (Cp = η5-C5H5) in boiling methanol, bis(cyclopentadienyl)-methoxytitanium(IV) cyanide, Cp2Ti(OCH3)CN, is formed which in air is converted into the dinuclear oxygen-bridged derivative (Cp2TiCN)2O. By the same procedure, the bis(methylcyclopentadienyl) analogue [MeCp2TiCN]2O has been obtained. An X-ray diffraction study of (Cp2TiCN)2O has shown that the CN group acts as a unidentate ligand with a Ti? C bond length of 2.158 Å and a Ti? C? N bond angle of 177.7°, very close to linearity. The Ti? O bond distance, 1.836 Å, and the bond angle at the bridging O atom, 174.1°, are normal. The ligands are arranged in a nearly tetrahedral way around the Ti atoms. The structural results are compared to those for similar dinuclear titanium complexes.  相似文献   
7.
The crystal and molecular structure of Bis(η5-cyclopentadienyl)titanium(IV) dibromide, Ti(η5?C5H5)2Br2, has been investigated by an X-ray structure determination. Crystal data: triclinic, a = 7.872(5), b = 11.807(5), c = 12.310(3) Å, α = 107.62(3), β = 100.83(4), γ = 90.69(4)°, V = 1 068(14) Å3, T = 293, space group P1 , Z = 4 (there are two crystallographically independent molecules in the asymmetric unit cell and their conformations are similar). Final R and Rw values are 0.068 and 0.073, respectively. The structural results are compared to those for similar type molecules.  相似文献   
8.
The structure of the title compound, Na2[Zn(C6H11O2)4], consists of two‐dimensional polymeric sheets. The Zn2+ ions are approximately tetrahedrally coordinated by O atoms from different hexanoate anions. Both Na+ ions are six‐coordinated by carboxyl­ate O atoms. One of the hexanoate O atoms is attached to one Zn2+ ion and one Na+ ion, and the remaining O atom is attached to two Na+ ions.  相似文献   
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