STEREOCHEMISTRY OF ARSENIC: PART VI. TRI-p-TOLYLARSINE

1963 ◽  
Vol 41 (1) ◽  
pp. 14-17 ◽  
Author(s):  
J. Trotter
Keyword(s):  
Van Der Waals ◽  
Lone Pair ◽  
Unit Cell ◽  
Van Der Waals Interactions ◽  
Ideal Model ◽  
Cell Axis ◽  
Bond Lengths ◽  
Cell Dimensions ◽  
Intermolecular Contacts ◽  
The Ideal

Crystals of tri-p-tolylarsine are rhombohedral, with cell dimensions a = 9.84 Å, α = 80° 2′, and space group [Formula: see text]. There are two molecules in the unit cell, and hence the molecule has symmetry C3. The structure has been determined from a projection along the rhombohedral cell axis, and the bond lengths and valency angles are given. In comparison with an ideal model having maximum interaction between the arsenic lone pair and the aromatic π-electrons, each ring is rotated about its As—C bond by 36°, the three rotations being in the same sense. These displacements increase overcrowded distances in the ideal model to about the normal van der Waals separations, the closest intramolecular contacts between p-tolyl groups being [Formula: see text] and [Formula: see text]. All the intermolecular contacts correspond to van der Waals interactions.

STEREOCHEMSTRY OF ARSENIC: PART III. o-PHENYLENEDIARSINE OXYCHLORIDE

1962 ◽  
Vol 40 (6) ◽  
pp. 1113-1117 ◽  
Author(s):  
W. R. Cullen ◽  
J. Trotter
Keyword(s):  
Symmetry Axis ◽  
Van Der Waals ◽  
Membered Ring ◽  
Unit Cell ◽  
The Other ◽  
Van Der Waals Interactions ◽  
Chlorine Atoms ◽  
Space Group ◽  
Bond Lengths ◽  
Aromatic Character

Crystals of o-phenylenediarsine oxychloride, C6H4As2Cl2O, are monoclinic with four molecules in a unit cell of dimensions a = 14.50, b = 8.38, c = 7.66 Å, β = 105.8°, space group C2/c. The structure has been determined from projections along the b and c axes. Each molecule is situated on a 2-fold symmetry axis and is planar except for the chlorine atoms, which lie one on either side of the plane of the other atoms. The values of the bond lengths and valency angles have been obtained. Abnormal valency angles at the arsenic and oxygen atoms are the result of their presence in the five-membered ring, and the unusual stability of the molecule in spite of these angles can be interpreted in terms of aromatic character, involving dπ–pπ bonding. The intermolecular separations correspond to normal van der Waals interactions.

scholarly journals ReNF4 · ReF5(NCl), ein Nitrido-Nitrenokomplex von Rhenium(VII)/ ReNF4 · ReF5(NCl), a Nitrido Nitrene Complex of Rhenium (VII)

1984 ◽  
Vol 39 (8) ◽  
pp. 1114-1117 ◽  
Author(s):  
Willi Kafitz ◽  
Kurt Dehnicke ◽  
Eberhard Schweda ◽  
Joachim Strähle
Keyword(s):  
Ir Spectrum ◽  
Fluorine Atom ◽  
Structural Investigation ◽  
Unit Cell ◽  
Trans Position ◽  
X Ray ◽  
Bond Lengths ◽  
Direct Fluorination ◽  
Cell Dimensions ◽  
In Trans

AbstractReNF4 · ReF5(NCl) is prepared by direct fluorination of ReNCl4 with fluorine between 80 °C and 130 °C. The red crystals are extremely sensitive to moisture. The complex is characterized by the IR spectrum and by an X-ray structural investigation. ReNF4 · ReF5(NCl) crystallizes orthorhombically in the space group Pnma with 4 formula units per unit cell and with the cell dimensions a = 1440, b = 848, c = 776 pm (419 observed, independent reflexions, R = 13.9%). The complex consists of the molecules ReNF4 and ReF5(NCl), which are linked by a linear asymmetric fluorine bridge. The bridging fluorine atom is in trans-position to the nitrido ligand Re -F - 228 pm) and to the nitreno ligand (Re -F = 159 pm and Re= N - Cl 164 pm) correspond to triple 188 pm). The Re ≡ N bond lengths Re= N bonds.

scholarly journals van der Waals Interactions and Hadron Resonance Gas: Role of resonance widths modeling on conserved charges fluctuations

2018 ◽  
Vol 171 ◽  
pp. 14006
Author(s):  
Volodymyr Vovchenko ◽  
Paolo Alba ◽  
Mark I. Gorenstein ◽  
Horst Stoecker
Keyword(s):  
Lattice Qcd ◽  
Temperature Region ◽  
Van Der Waals ◽  
Baryon Number ◽  
The Other ◽  
Van Der Waals Interactions ◽  
Crossover Temperature ◽  
Lattice Data ◽  
The Ideal

The quantum van der Waals (QvdW) extension of the ideal hadron resonance gas (HRG) model which includes the attractive and repulsive interactions between baryons – the QvdW-HRG model – is applied to study the behavior of the baryon number related susceptibilities in the crossover temperature region. Inclusion of the QvdW interactions leads to a qualitatively different behavior of susceptibilities, in many cases resembling lattice QCD simulations. It is shown that for some observables, in particular for χBQ11/χB2, effects of the QvdW interactions essentially cancel out. It is found that the inclusion of the finite resonance widths leads to an improved description of χB2, but it also leads to a worse description of χBQ11/χB2, as compared to the lattice data. On the other hand, inclusion of the extra, unconfirmed baryons into the hadron list leads to a simultaneous improvement in the description of both observables.

scholarly journals Evaluation of dispersion type metal···π arene interaction in arylbismuth compounds – an experimental and theoretical study

2018 ◽  
Vol 14 ◽  
pp. 2125-2145 ◽  
Author(s):  
Ana-Maria Preda ◽  
Małgorzata Krasowska ◽  
Lydia Wrobel ◽  
Philipp Kitschke ◽  
Phil C Andrews ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Van Der Waals ◽  
Structural Features ◽  
Van Der Waals Interactions ◽  
Model Systems ◽  
Bismuth Atom ◽  
Dispersion Energy ◽  
Space Group ◽  
Intermolecular Contacts ◽  
London Dispersion

The dispersion type Bi···π arene interaction is one of the important structural features in the assembly process of arylbismuth compounds. Several triarylbismuth compounds and polymorphs are discussed and compared based on the analysis of single crystal X-ray diffraction data and computational studies. First, the crystal structures of polymorphs of Ph3Bi (1) are described emphasizing on the description of London dispersion type bismuth···π arene interactions and other van der Waals interactions in the solid state and the effect of it on polymorphism. For comparison we have chosen the substituted arylbismuth compounds (C6H4-CH═CH2-4)3Bi (2), (C6H4-OMe-4)3Bi (3), (C6H3-t-Bu2-3,5)3Bi (4) and (C6H3-t-Bu2-3,5)2BiCl (5). The structural analyses revealed that only two of them show London dispersion type bismuth···π arene interactions. One of them is the styryl derivative 2, for which two polymorphs were isolated. Polymorph 2a crystallizes in the orthorhombic space group P212121, while polymorph 2b exhibits the monoclinic space group P21/c. The general structure of 2a is similar to the monoclinic C2/c modification of Ph3Bi (1a), which leads to the formation of zig-zag Bi–arenecentroid ribbons formed as a result of bismuth···π arene interactions and π···π intermolecular contacts. In the crystal structures of the polymorph 2b as well as for 4 bismuth···π arene interactions are not observed, but both compounds revealed C–HPh···π intermolecular contacts, as likewise observed in all of the three described polymorphs of Ph3Bi. For compound 3 intermolecular contacts as a result of coordination of the methoxy group to neighboring bismuth atoms are observed overruling Bi···π arene contacts. Compound 5 shows a combination of donor acceptor Bi···Cl and Bi···π arene interactions, resulting in an intermolecular pincer-type coordination at the bismuth atom. A detailed analysis of three polymorphs of Ph3Bi (1), which were chosen as model systems, at the DFT-D level of theory supported by DLPNO-CCSD(T) calculations reveals how van der Waals interactions between different structural features balance in order to stabilize molecular arrangements present in the crystal structure. Furthermore, the computational results allow to group this class of compounds into the range of heavy main group element compounds which have been characterized as dispersion energy donors in previous work.

scholarly journals 2,6-Bis(4-methoxyphenyl)-1,4-dithiine

2014 ◽  
Vol 70 (2) ◽  
pp. o137-o137 ◽  
Author(s):  
Sha-Sha Zhao ◽  
Qiong Su ◽  
Zhi-Hong Peng ◽  
De-Lie An
Keyword(s):  
Aromatic Ring ◽  
Crystal Packing ◽  
Lone Pair ◽  
Van Der Waals Interactions ◽  
Boat Conformation ◽  
Asymmetric Unit ◽  
Torsion Angles ◽  
Rotation Symmetry ◽  
Bond Lengths ◽  
Title Molecule

The title molecule, C18H16O2S2, reveals crystallographic twofold rotation symmetry (with both S atoms lying on the axis) and one half-molecule defines an asymmetric unit. The dithiine ring is in a boat conformation. The aromatic ring and the C=C bond are nearly coplanar, with small torsion angles of −171.26 (19) and 8.5 (3)°. The two S—C bond lengths [1.7391 (19) and 1.7795 (18) Å] are shorter than single C—S bonds and longer than analogous C=S double bonds, which indicates a certain degree of conjugation between the lone pair on the S atom and π electrons of the C=C bond. The crystal packing only features van der Waals interactions.

scholarly journals Matrix Isolation FTIR and Theoretical Study of Weakly Bound Complexes of Isocyanic Acid with Nitrogen

Molecules ◽  
2022 ◽  
Vol 27 (2) ◽  
pp. 495
Author(s):  
Justyna Krupa ◽  
Maria Wierzejewska ◽  
Jan Lundell
Keyword(s):  
Van Der Waals ◽  
Matrix Isolation ◽  
Lone Pair ◽  
Nitrogen Molecule ◽  
Van Der Waals Interactions ◽  
Isocyanic Acid ◽  
Weakly Bound ◽  
Isolation Technique ◽  
Weak Complexes ◽  
Argon Matrices

Weak complexes of isocyanic acid (HNCO) with nitrogen were studied computationally employing MP2, B2PLYPD3 and B3LYPD3 methods and experimentally by FTIR matrix isolation technique. The results show that HNCO interacts specifically with N2. For the 1:1 stoichiometry, three stable minima were located on the potential energy surface. The most stable of them involves a weak, almost linear hydrogen bond from the NH group of the acid molecule to nitrogen molecule lone pair. Two other structures are bound by van der Waals interactions of N⋯N and C⋯N types. The 1:2 and 2:1 HNCO complexes with nitrogen were computationally tracked as well. Similar types of interactions as in the 1:1 complexes were found in the case of the higher stoichiometry complexes. Analysis of the HNCO/N2/Ar spectra after deposition indicates that the 1:1 hydrogen-bonded complex is prevalent in argon matrices with a small amount of the van der Waals structures also present. Upon annealing, complexes of the 1:2 and 2:1 stoichiometry were detected as well.

A precise analysis of the 1H nuclear magnetic resonance spectrum of 2-phenyl-1,3-dithiane. Ring pucker, signs of long-range J(H,H), internal rotational barrier, and van der Waals shifts

1994 ◽  
Vol 72 (7) ◽  
pp. 1722-1727 ◽  
Author(s):  
Ted Schaefer ◽  
Jeremy P. Kunkel ◽  
Robert W. Schurko ◽  
Guy M. Bernard
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nuclear Magnetic Resonance Spectrum ◽  
Resonance Spectrum ◽  
Chemical Shifts ◽  
Van Der Waals ◽  
Lone Pair ◽  
Coupling Constants ◽  
Van Der Waals Interactions ◽  
Nuclear Magnetic

The 1H nuclear magnetic resonance spectrum of 2-phenyl-1,3-dithiane, as a dilute solution in a CS2–C6D12–TMS solvent mixture at 300 K, is analyzed to yield 8 chemical shifts and 22 distinct coupling constants, nJ(H,H), n = 2–6. The coupling constant between H-2 and the para proton indicates, first, that the bisected conformer (phenyl plane perpendicular to the pseudo plane of the dithiane ring) is most stable and, second, that the apparent twofold barrier to rotation about the Csp2—Csp3 bond is 9.6 kJ/mol. The AM1, STO-3G, and STO-3G* computations confirm the twofoldedness of the barrier; the AM1 barrier is 9.4 kJ/mol. The empirical equation, [Formula: see text] reproduces the vicinal coupling constants of the CH2CH2CH2 fragments and implies puckering angles [Formula: see text] of 54°, 61°, and 64°, respectively. It is implied that 3J at [Formula: see text] is larger than at [Formula: see text] This results is discussed in terms of the latest theoretical approach to 3J in the HCCH fragment. The 4J(H,H) signs and magnitudes for the CH2CH2CH2 fragment agree reasonably well with theory. For the CH2SCH fragment, 4J(H,H) values are positive, in contrast to corresponding numbers in the propanic fragment, perhaps the first experimental values for certain rigid orientations about a heteroatom. INDO MO FPT computations on propane, dimethyl ether, and dimethyl sulfide confirm the experimental trend in 4J(H,H). 2J(H,H) and 5J(H,H) values are compared to those in related molecules. The striking differential shifts of the axial and equatorial protons are attributed to differential van der Waals interactions with the 3p lone-pair orbital on sulfur. A comparison of the ring proton chemical shifts with those in phenylcyclohexane and isopropylbenzene implies that C—S bonds are weaker net electron donors by hyperconjugation than are C—C bonds. It is also proposed that the ortho protons are deshielded by intramolecular van der Waals interactions with the 3p orbitals on the sulfur atoms.

STEREOCHEMISTRY OF ARSENIC: VIII. CYANODIMETHYLARSINE (CACODYL CYANIDE)

1963 ◽  
Vol 41 (2) ◽  
pp. 460-464 ◽  
Author(s):  
N. Camerman ◽  
J. Trotter
Keyword(s):  
Charge Transfer ◽  
Lone Pair ◽  
The Other ◽  
Van Der Waals Interactions ◽  
Mean Values ◽  
Bond Lengths ◽  
Nitrogen Lone Pair ◽  
The Mean ◽  
Lone Pair Electrons ◽  
Crystallographic Axes

Crystals of cyanodimethylarsine, (CH3)2AsCN, are triclinic with two molecules in a unit cell of dimensions a = 6.31, b = 8.02, c = 6.27 Å, α = 110°00′, β = 119°45′, γ = 81°47′, space group [Formula: see text]. The structure has been determined from projections along the three crystallographic axes, and the mean values of the bond lengths and valency angles (with estimated standard deviations) are: As—C = 1.96±0.03 Å, C—N = 1.16 ± 0.07 Å, [Formula: see text], [Formula: see text], [Formula: see text]. There is an unusually short As … N intermolecular separation, which is indicative of charge-transfer bonding involving donation of nitrogen lone pair electrons to vacant arsenic 4d orbitals; the other intermolecular approaches correspond to normal van der Waals interactions.

scholarly journals Crystal structure of tris(phenylselenolato-κSe)tris(tetrahydrofuran-κO)thulium(III)

2014 ◽  
Vol 70 (11) ◽  
pp. m389-m389
Author(s):  
Esther M. Takaluoma ◽  
Raija Oilunkaniemi ◽  
Christian W. Lehmann ◽  
Risto S. Laitinen
Keyword(s):  
Crystal Structure ◽  
Title Compound ◽  
Rotation Axis ◽  
Van Der Waals ◽  
Van Der Waals Interactions ◽  
Octahedral Coordination ◽  
Coordination Environment ◽  
Bond Angles ◽  
Bond Lengths

In the title compound, [Tm(C6H5Se)3(C4H8O)3], the TmIIIatom lies on a threefold rotation axis and is coordinated by three phenylselenolate ligands and three tetrahydrofuran ligands leading to a distortedfac-octahedral coordination environment. The Tm—Se and Tm—O bond lengths are 2.7692 (17) and 2.345 (10) Å, respectively, and the bond angles are 91.32 (6)° for Se—Tm—Se, 92.6 (2) and 94.4 (2)° for Se—Tm—O, and 81.2 (3)° for O—Tm—O. In the crystal, the discrete complexes are linked by van der Waals interactions only. The crystal was refined as a non-merohedral twin (ratio = 0.65:0.35).

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