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11

Digitale Medien

Multiple bonding as a screening phenomenon (1982)

Boeyens, Jan C. A.

Springer

Journal of chemical crystallography 12 (1982), S. 245-254

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ISSN: 1572-8854

Quelle: Springer Online Journal Archives 1860-2000

Thema: Geologie und Paläontologie , Physik

Notizen: Abstract The elimination of a ligand pair from contiguous atoms in a molecule increases the bond order between them by unity as the remnant electrons rearrange into a suitable molecular orbital. Starting from experimental single-bond Morse curves, it is shown that screening of the internuclear repulsion by these electrons accounts for almost the total increase in bond strength during the formation of double and triple bonds. Reverse screening has a similar though smaller effect on adjacent single bonds, and observed trends can be accounted for adequately by the same mechanism.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01195716

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12

Digitale Medien

Crystal and molecular structure of biruthenocene (1982)

Levendis, Demetrius C. ; Boeyens, Jan C. A. ; Neuse, Eberhard W.

Springer

Journal of chemical crystallography 12 (1982), S. 493-506

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ISSN: 1572-8854

Quelle: Springer Online Journal Archives 1860-2000

Thema: Geologie und Paläontologie , Physik

Notizen: Abstract Crystalline biruthenocene is disordered at room temperature. The apparent symmetry ofP21 c applies to an average structure only. Better resolution is achieved by refinement in the space groupP1. The room-temperature X-ray structure, as refined in both space groups, shows that the mutual orientation of cyclopentadienyl rings within a sandwich is not conformationally important and that it depends on intermolecular interactions.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01160903

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13

Digitale Medien

Crystal structure of the Ni(ClO4)2 complex of the mixed donor macrocycle, 9-ane N2O: Resolution of disorder by force-field calculation (1984)

Boeyens, Jan C. A. ; Hancock, Robert D. ; Thöm, Vivienne J.

Springer

Journal of chemical crystallography 14 (1984), S. 261-268

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ISSN: 1572-8854

Quelle: Springer Online Journal Archives 1860-2000

Thema: Geologie und Paläontologie , Physik

Notizen: Abstract The crystal structure of the nickel perchlorate complex of the macrocyclic ligand 9-ane N2O [Ni(ClO4)2·C12H28N4O2] has been determined by X-ray diffraction. The observed space group,Cm (No. 28), occurs because of disorder across the mirror plane. The disorder was resolved by force-field calculation and superposition of the calculated structures in a molecular trial-and-error procedure. The coordination geometry is octahedral and the centrosymmetric cation contains a pseudo-three-fold axis.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01161163

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14

Digitale Medien

Crystal structures of two isomeric oximes. (EE)-2-methyl-3-phenyl-3-thiocyanatopropenaldoxime and (Z)-5-methyl-6-phenyl-1,3-thiazin-2-one oxime (1996)

Boeyens, Jan C. A. ; Cook, Leanne M. ; Ngoi, Tak-ho ; [weitere]

Springer

Journal of chemical crystallography 26 (1996), S. 215-218

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ISSN: 1572-8854

Schlagwort(e): Isomeric oximes ; X-ray diffraction ; heterocyclic isomer

Quelle: Springer Online Journal Archives 1860-2000

Thema: Geologie und Paläontologie , Physik

Notizen: Abstract The crystal structure of two isomeric oximes, C11N10N2OS have been studied by X-ray diffraction. The open-chain thiocyanato derivative is somewhat'less dense and crystallizes with the orthorhombic space group Pbcn;a,b,c=18.718(1), 10.601(3), 11.528(1) Å,Z=8. The heterocyclic isomer occurs as pseudo-orthorhombic (Cmma)twinned crystals of space group P21/n, a, b, c, β=12.11(1), 7.46(1), 12.12(1) Å, 100.09(1)o,Z=4. Twinning occurs as a result of the near-equality of the monoclinica andc cell constants.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01673673

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15

Digitale Medien

The importance of inter-molecular forces in crystal structure analysis: Solid state study of the diag-to-lat isomerization of (η5-C5H4Me)Re(CO)2Br2 (1998)

Boeyens, Jan C. A. ; Cheng, Lin ; Coville, Neil J. ; [weitere]

Springer

Journal of chemical crystallography 28 (1998), S. 185-191

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ISSN: 1572-8854

Schlagwort(e): Isomerization ; solid state ; inter-molecular forces

Quelle: Springer Online Journal Archives 1860-2000

Thema: Geologie und Paläontologie , Physik

Notizen: Abstract Single crystal X-ray structures of diag and lat-(η5-C5H4Me)Re(CO)2Br2 have been determined. The diag form crystallizes in the triclinic space group $${P\bar 1}$$ , a = 6.751(2), b = 8.537(1), c = 9.758(1) Å α = 96.70(1), β = 93.15(2), γ = 104.96(2)°, V = 534.8(2) Å3, Z = 2. The lat form is monoclinic, P21/c, a = 11.820(1), b = 7.133(1), c = 12.924(1) Å β = 98.278(8)°, V = 1078.2(2) Å3, Z = 4. The unit cell volumes (per Z) of the two isomers differ by ca 1%. Molecular modelling reveals an energy difference between the two isomers of 1 kJ mol−1 or less. The XRD powder diffraction patterns for the lat isomer produced by crystallization from solution or prepared by thermal isomerization are identical. The evidence thus suggests that the solid state isomerization reaction is a novel example of a reaction which yields a molecular structure determined by crystal packing forces.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1022466126100

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16

Digitale Medien

Identification of the conformational type of seven-membered rings (1980)

Boessenkool, Ideletta K. ; Boeyens, Jan C. A.

Springer

Journal of chemical crystallography 10 (1980), S. 11-18

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ISSN: 1572-8854

Quelle: Springer Online Journal Archives 1860-2000

Thema: Geologie und Paläontologie , Physik

Notizen: Abstract A scheme for the complete characterization of seven-membered ring conformation is described. Parameters of puckering which are calculated directly from crystallographic coordinates are used to map the conformation onto a torus in relation to the various symmetrical forms.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01209549

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17

Digitale Medien

The mono- and bis-(trichloroacetic acid)-solvates of ferricenium trichloroacetate (1984)

Neuse, Eberhard W. ; Loonat, Rokaya ; Boeyens, Jan C. A.

Springer

Transition metal chemistry 9 (1984), S. 12-17

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ISSN: 1572-901X

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Notizen: Summary Inconsistent literature reports on the preparation of the mono- and bis-(trichloroacetic acid)-solvated ferricenium trichloroacetates, (1) and (2) have prompted a comprehensive investigation of the experimental conditions giving rise to the formation of the two ferricenium salts. In agreement with the majority of authors, (2) is reproducibly obtained from trichloroacetic acid and ferrocene in molar ratios of 3 and higher in benzene over a wide range of experimental variables in the presence of air or, preferably, under conditions of oxygen saturation. Treatment of aqueous ferricenium sulfate solutions with trichloroacetic acid in an acid/ferrocene ratio of 3 and above affords the di-solvate, whereas at lower reactant ratios, and under conditions of reduced acidity, formation of the mono-solvate prevails. More efficiently, and in a higher degree of purity, the latter salt is generated from the former by a controlled recrystallization from water. Representative spectroscopic features of the two salts are discussed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00620720

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