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  • General Chemistry  (21)
  • crystal structure  (5)
  • Staphylococcal Nuclease  (2)
  • 1
    Electronic Resource
    Electronic Resource
    A Novel Cluster Consisting of Seven Fused MX6 Octahedra, Li14(THF)8[Ni7Cl17(μ-formamidinate)3(μ-Cl)]2 (2000)
    Springer
    Journal of cluster science 11 (2000), S. 87-94 
    Details
    ISSN: 1572-8862
    Keywords: nickel cluster ; fluorinated formamidine ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract When a THF solution made from equimolar amounts of methyllithium and N,N′-bispentafluorophenyl formamidine, C6F5NC(H)N(H)C6F5, was added to a suspension of NiCl2 in THF and the mixture refluxed for 12 h, a bright yellow-green solution was formed, from which a bright green crystalline compound was obtained in 〉60% yield upon partial evaporation of the solvent. This compound, Li14(THF)8[Ni7Cl17(μ-formamidinate)3(μ-Cl)]2·9.4THF, crystallizes in the tetragonal space group P4 2/mnm (No. 136) with Z=2. The core consists of two Ni7 units bridged by two Cl atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009008630342
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  • 2
    Electronic Resource
    Electronic Resource
    A double-bonded niobium(III) compound with a formamidinate core: Nb2(μ-SMe)2(μ-DTolF)2 (η2-DTolF)2.2 toluene, DToIF= di-p-tolylformamidinate (1996)
    Springer
    Journal of cluster science 7 (1996), S. 655-662 
    Details
    ISSN: 1572-8862
    Keywords: Niobium(III) ; edge-sharing bioctahedra ; di-p-tolylformamidinato ; thiomethoxide ; double-bond ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The reaction of NaEt3BH with Nb2(μ-SMe2)3Cl6 results in the transfer of a hydride ion to dimethylthioether with concomitant production of methane. Further reaction with potassium di-p-tolylformamidinate, KDTolF, yields Nb2(μ-SMe)2(μ-DTolF)2η2-DTolF:)2.2 toluene, 1. In the latter, two thiomethoxide ions and two DTolF groups bridge the trivalent niobium atoms. Each of the other two DTolF groups chelate a metal atom to give the molecule an edge-sharing bioctahedral structure, The niobium-niobium distance of 2.655(2) A is consistent with the presence of a double bond between the metal atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01165807
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  • 3
    Electronic Resource
    Electronic Resource
    The W2Cl4(NHCMe3)2(PR 3)2 molecules (R 3=Me3, Et3, Pr n 3, Me2Ph) I. Their isomeric forms, interconversion proeesses, crystalline forms, and detailed molecular structures (1994)
    Springer
    Journal of cluster science 5 (1994), S. 11-36 
    Details
    ISSN: 1572-8862
    Keywords: Tungsten ; isomeric forms ; crystal structure ; triple bonds ; interconversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A thorough study of compounds with the formula W2Cl4(NHCMe3)2(PR3)2, withR 3=Me3, Et3, Prg n 3 Me2,Ph, is reported. In addition to the previously reported crystalline compounds, namely Ia,trans-W2Cl4(NHCMe3)2(PMe3)2 in space group Pmmn;3a,trans-W2Cl4(NHCM3)2(PEt3)2 in space group P21/a (or P21/c); and4,cis-W2Cl4(NHCMe3)2(PMe2Ph)2 in Pna21, we have obtained and structurally characterized the following new substances,1b,trans-W2Cl4,(NHCMe3)2(PMe2)2, space group P21/c,a= 12.233 (4) Å,b= 12.872 (4) Å,c=17.095 (5) Å,β=93.52 (2)°,Z=4,V=2687 (1) Å3 2,cis-W2Cl4(NHCMe3)2(PMe3)2, P21/c,a=9.673 (4) Å,b=17.249 (4) Å,c=16.244 (5) Å,β=99.63 (3),Z = 4 ,V=2669 (1) Å.3b,trans-W2Cl4(NHCMe3)2(PEt3)2, Pl,a=16.850 (3) Å,b=17.797 (3) Å,c= 11.459 (2)Å,α= 101.02 (1),β= 103.13°, y=84.23 (1)°,Z=4,V= 3279 (1) Å5,trans-W2Cl4(NHCM3)2(PMe2Ph)2, Fdd2,a=39.563 (8) Å at 20°C; 39.325 (10) Å at -6O°C,b = 57.543 (17) Å at 20°C; 57.186 (16) Å at -60°C,c= 8.810 (1) Å at 20°C; 8.770 (1) Å at - 60°C ,Z=24,V=20057 (7) Å3 (20°C), 19723 (8) Å3 ( - 60°C) .6,trans-W2Cl4(NHCMe3 2(PPrn 3)2, Pl,a= 17.287 (2) Å (20°C); 17.077 (5) Å (-60°C),b= 19.119 (2) Å (20°C); 18.952 (6) Å (-60°C),c= 12.713 (1) Å (20°C); 12.668 (4) Å (-60°C),Z=4,V= 3980 (1) Å3 (20°C), 3898 (2) ,Å3 ( - 60°C). In addition, the structure of3a was re-determined and refined so that the disorder ratio was a refined parameter, leading to a value of 0.520:0.480 instead of being arbitrarily fixed at 0.50:0.50. In all of the structures the molecules are held in eclipsed (but very distorted) rotational conformations and the W-W distances are all within the range of 2.305-2.330 Å. As will be shown in a later paper, for all phosphines, thecis andtrans isomers are of similar stability and an equilibrium mixture exists in solution. It is also shown that1a and3a do not contain unexpectedly short W-N bonds as previously reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01165490
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  • 4
    Electronic Resource
    Electronic Resource
    Staphylococcal nuclease reviewed: A Prototypic study in contemporary enzymology. II. Solution studies of the nucleotide binding site and the effects of nucleotide binding. (1979)
    Springer
    Molecular and cellular biochemistry 23 (1979), S. 3-16 
    Details
    ISSN: 1573-4919
    Keywords: Nuclease ; Staphylococcal Nuclease ; Micrococcal Nuclease ; Enzyme Function and Structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary This is the second of a series of four articles in which the chemical, enzymological and crystallographic work on Ribonucleate (deoxyribonucleate)-3′-nucleotidohydrolase EC 3.1.4.4 (staphylococcal nuclease, micrococcal nuclease) will be reviewed and correlated. This article discusses studies in solution delineating the extent of the binding site of the enzyme and identifying some of the particular amino acid residues that form this site. In addition, the effects of the very potent inhibitory combination of thymidine-3′,5′-diphosphate and Ca2+ on the conformation of the enzyme and its physical, chemical and enzymological properties will be reviewed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00226675
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  • 5
    Electronic Resource
    Electronic Resource
    The structure of Mo4Cl8(PEt3)4: How unrecognized disorder previously reduced the quality of the refinement (1991)
    Springer
    Journal of cluster science 2 (1991), S. 121-129 
    Details
    ISSN: 1572-8862
    Keywords: Molybdenum tetranuclear cluster ; rectangular ; triethylphosphine ligand ; preparation ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The preparation and structure of the title compound were reported several years ago by McCarly and co-workers ((1978).J. Am. Chem. Soc. 100, 7900). Curiously, it was reported that refinement of the structure converged at exceptionally high figures of merit (R=0.126;R w =0.158), but no reason was given. In view of a recent observation in this laboratory (Chen and Cotton (1991).J. Am. Chem. Soc. 113, 5857) that a similar type of compound, [Re4Cl8(μ-O)2(μ-OMe)2]2− exhibited a subtle but elegant disorder, we reexamined the crystal structure of the title compound. It is found to have 92% of the Mo4 rectangles in one orientation (the only one previously included in the refinement) and 8% in an orientation perpendicular to the main one. In both orientations the ligand positions are approximately the same. The figures of merit are nowR=0.041;R w =0.064. The three structure parameters previously reported are now only slightly different: Mo-Mo=2.210(1) vs. 2.211(3) Å; Mo-Mo'=2.897(1) vs. 2.901(2) Å; angle Mo-Clb-Mo=74.2[8]° vs. 74.4(2)°. We report here the complete structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00702953
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  • 6
    Electronic Resource
    Electronic Resource
    Further studies of M3(μ3-O)(μ-X)3(μ-O2CCH3)3L3 (M=Mo, W) type clusters with nine core electrons (1992)
    Springer
    Journal of cluster science 3 (1992), S. 123-144 
    Details
    ISSN: 1572-8862
    Keywords: Molybdenum ; tungsten ; crystal structure ; reduction ; acetate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Four new compounds having nine cluster electrons and cores of the types Mo3OCl3, Mo3OBr3, and W3OCl3 are reported. Compound (1) prepared by reduction of [Bu4N][Mo3OCl6(OAc)3] in THF with metallic zinc, was shown by X-ray crystallography to be Mo3OCl4(OAc)3 (THF)2 (1). It forms crystals in space groupP21 with unit cell dimensionsa=9.472(2) Å,b=13.546(4) Å,c=9.652(2) Å, β=101.70(2)°,V=1201(1) Å3,Z=2. The [Mo3(μ3-O)(μ-Cl)3]4+ core is surrounded by three μ-O2CCH3 anions, one Cl−, and two THF and has Mo-Mo distances of 2.620(1) Å, 2.613(1) Å, and 2.530(1) Å, with the shortest bond between the two Mo atoms to which the THF molecules are coordinated. Compounds [Bu4N]2 [Mo3OBr6(O2CCH3)3] · Me2CO, (2) and [Mo3OBr3(O2CCH3)3(PMe3)3]3 · BF4, (3) are the first two nine-electron Mo3 species with a [Mo3(μ3-O) Br3]4+ core. Both were obtained by zinc reduction of [Mo3OBr6(O2CCH3)3]− in the presence of (NBu4) Br (2) or PMe3 and NaBF4 (3), and each was characterized crystallographically. Compound (2) crystallized in space group Cc with unit cell dimensionsa=25.037(5) Å,b=12.827(2) Å,c=21.484(4) Å, β=122.96(1)0,V=5790(3) Å3,Z=4. While the anion has no crystallographically required symmetry, its virtual symmetry is C3v . The Mo-Mo distances are 2.619(2) Å, 2.610(3) Å, 2.644(2) Å, with a mean value of 2.624[14] Å. Compound (3) crystallized in space groupP21/c with unit cell dimensionsa=10.846(2) Å,b=25.033(5) Å,c=12.641(5) Å, β=94.74(2)0,V=3420(2) Å3,Z=4. The cation occupies a general position but has virtual C3v symmetry, with Mo-Mo distances of 2.601(2) Å, 2.610(2) Å, 2.627(2) Å, with a mean value of 2.613[14] Å. Thus the anionic and cationic Mo3 clusters in (2) and (3), respectively, have average Mo-Mo distances that are equal within experimental error. Compound (4), [NEt4]2 [W3OCl6(O2CCH3)3] is the first 9-electron compound of this type containing tungsten. It was prepared by reduction of [Et4N][W3OCl6(OAc)3] in benzene with Na/Hg. It crystallized in space groupP212121 with unit cell dimensionsa=11.076(2) Å,b=14.345(2) Å,c=21.026(3) Å,V=3574(1) Å3,Z=4. The anion resides on a general position but has virtual C3v symmetry, with W-W distances of 2.577(1) Å, 2.612(1) Å, 2.584(1) Å and a mean value of 2.591[15] Å.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00702878
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  • 7
    Electronic Resource
    Electronic Resource
    Staphylococcal nuclease reviewed: A prototypic study in contemporary enzymology (1979)
    Springer
    Molecular and cellular biochemistry 23 (1979), S. 131-141 
    Details
    ISSN: 1573-4919
    Keywords: Nuclease ; Staphylococcal Nuclease ; Micrococcal Nuclease ; Protein Folding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary This is the last in a series of four articles in which the chemical, enzymological and crystallographic work on Ribonucleate (deoxyribonucleate)-3′-nucleotidohydrolase, EC 3.1.4.4 (staphylococcal nuclease, micrococcal nuclease) will be reviewed and correlated. This article discusses the use of the nuclease as a model system for the study of the mechanisms and energetics of the folding-unfolding reaction in proteins and for the study of the interrelationships between amino acid sequence and three-dimensional structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00219452
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  • 8
    Electronic Resource
    Electronic Resource
    Neuartiges Beispiel einer Dichromverbindung mit superkurzer CrCr-VierfachbindungDiese Arbeit wurde von der National Science Foundation unterstützt. (1978)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 90 (1978), S. 1015-1016 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19780901231
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  • 9
    Electronic Resource
    Electronic Resource
    [U3(μ3-Cl)2(μ1,η2-AlCl4)3(η6-C6Me6)3(][AlCl4] - ein dreikerniger UIII-ArenkomplexDiese Arbeit wurde von der Robert A. Welch Foundation (Grant No. A-494) gefördert. (1986)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 98 (1986), S. 652-654 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19860980723
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  • 10
    Electronic Resource
    Electronic Resource
    Dreikernige Cluster „elektronenarmer“ Übergangselemente (1980)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 92 (1980), S. 921-929 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dreikernige Cluster der „early transition elements“, das heißt der Elemente der linken Hälfte der Übergangsreihen, repräsentieren die einfachsten Clustertypen. Sie zeichnen sich durch außerordentlich starke Bildungstendenz und hohe Stabilität aus, so daß sie unter sehr verschiedenartigen Bedingungen entstehen und ihre dreieckigen M3-Gerüste bei Ligandenaustauschreaktionen erhalten bleiben. Diesen Clustern Kommt für die Chemie der erwähnten Elemente--besonders aus der 4d- und 5d-Serie - in mittleren Oxidationsstufen große Bedeutung zu. Im Falle von MoIV interessiert die Biorelevanz. Die Chemie, Molekül- und Elektronenstruktur solcher Verbindungen werden in diesem Fortschrittsbericht systematisch behandelt. Hierbei wird der Bezug zur kristallfeldtheoretischen Behandlung von einkernigen Metallkomplexen hergestellt.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19800921107
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