F. Baert

The molecular dipole moment of the non-linear optical 3-methyl 4-nitropyridine N-oxide molecule: X-ray diffraction and semi-empirical studies

The 3-methyl 4-nitropyridine N-oxide molecule (POM) is characterised by its weak dipole moment. The low polarity of this molecule results mainly from the electronic competition of the two electron-accepting groups, N-oxide and nitro. An accurate electron density distribution and the electrostatic potential around the molecule have been calculated from a high-resolution X-ray diffraction study. The data were collected at 123 K using graphite-monochromated Mo-Kα radiation to sin(θ)/λ= 1.24 A–1. Crystal data: C6H6O3N2, orthorhombic, space group P212121, a= 20.890, b= 6.094, c= 5.123 A, µ= 0.2 mm–1, λ= 0.71 A. The integrated intensities of 8000 reflections were measured and reduced to 2296 independent reflections with I 3σ(I). The experimental dipole moment is in a reasonable agreement with the semi-empirical calculations of the isolated molecule. The calculated net charges, the dipole moment and the electrostatic potential around the molecule deduced from this study reveal the nature of the intramolecular charge transfer due to the electron-accepting nitro and N-oxide groups.

Diastereocontrol of η4-α,β-unsaturated ketone–Fe(CO)3 complexation by an adjacent metal-complexed chiral centre

The reaction of tricarbonyl-[η6-3-(o-methyl- or o-methoxyphenyl)-1-phenylprop-2-en-1-onelchromium with nonacarbonyldi-iron gives specifically one diastereoisomer of the η4-Fe(CO)3–α,β-unsaturated ketone–η6 Cr(CO)3–ortho-substituted arene complex, the relative configuration (RS,SR) of which was unambiguously established by X-ray analysis; the equivalent reaction using the 3-m-methoxyphenylpropenone isomer gives a 1 : 1 mixture of two diastereoisomers.

7,15,23-Triphenyl-25,26,27-triethylester-2,3,10,11,18,19-hexahomo-3,9,11-trioxacalix[3]arene in a partial-cone conformation

Reaction of p-phenylhexahomocalix[3]arene (I-H) with bromomethyl acetate and potassium carbonate in acetone leads to the title triester derivative, (I-CH 2 CO 2 Et) {triethyl 7,15,23-triphenyl-3,11,19-trioxatetracyclo[19.3.1.1 5,9 .1 13,17 ]heptacosa-1(25),5,7,9(27),13,15, 17(26),21,23-nonaene-25,26,27-triyltris(oxyacetate), C 54 H 54 O 12 }, in a partial-cone conformation, which crystallizes with two molecules in the asymmetric unit. In this conformation, (I-CH 2 CO 2 Et) is adapted for selective complexation of the K + cation. We describe in this paper the synthesis and conformational behaviour of (I-CH 2 CO 2 Et) as determined by 1 H NMR spectroscopy and X-ray diffractometry

X-ray Structure of a New Pyrethroid, RU 52259

The X-ray structure of this intermediate compound, tert-butyl a-(tert-butylsulfonyl)-fl-(methoxysulfinyl)-3,3-dimethyl-2-[(3-phenoxybenzyl)oxycarbonyl]_ cyclopropaneprop ionate, shows the configuration of the asymmetric atoms at sites C1, C2 and S1 (C~,C t3 and fl-S) and allows the mechanism of its formation to be established. The bond distances in the molecule are in the expected range.

Calixcrown Binding to Caesium – X-Ray Structural Determination of a 1,3-Alternate Calix[4]arenebiscrown-7 Ligand

The crystal structure of calix[4]biscrown-7, 1, (C52H68O14), (triclinic,space group P1, Z = 2, a = 11.115 (5), b = 11.710 (5), c = 18.990 (7)Å, α = 85.12 (4), β = 93.11 (5), γ = 91.01 (5)4°,V = 2458.9 Å3, Rw = 0.0737 for 4170 ’observed‘, I ≤ 3σ (I),reflections) has been determined. It is suggested that the polyether loopswith a radius of ca. 2.1 Å are too shallow to efficiently complex theCs+ cation (radius = 1.69 Å).

Tricarbonyl(η6-3-methyl-2-vinylbenzoic acid)chromium

The benzylic deprotonation of tricarbonyl(η6-1-tert-butoxycarbonyl-2,3- dimethylbenzene)chromium occurs preferentially at the ortho position, whereas the meta position is still reactive but to a lesser extent. X-ray study of the title compound, [Cr(CO)3(C10H10O2)], obtained in a very good yield, confirms this result and shows a strong hydrogen bond between neighbouring carboxyl groups. The acid group and the phenyl ring are coplanar and the torsion angle between the phenyl ring and the vinyl group is 61.2°(4).

1,3-Di(ethoxy-ethoxy-methoxy)calix[4]-arene

In the solid state, the title compound, C 38 H 44 O 8 , adopts a cone conformation, which is somewhat distorted. The cone conformation is also observed by NMR spectroscopy in solution. The distortion consists of a major inward tilt of the two opposite phenolic rings, permitting hydrogen bonding to the ether substituents.

X-Ray Analysis and Proton Transfer Reaction in the Crystal of 2-(2′-Hydroxy-5′ -Methylphenyl)-5-Chloroben-zotriazole

Abstract Preliminary results of an x−ray crystal structure of 2−(2′−hydroxy−5′−methylphenyl)−5−chlorobenzotriazole at room temperature are presented as well as atomic parameters from an X−ray refinement and a TLS thernal vibration analysis on “heavy” atoms. These data allow the first step of an interpretation of the dynamics of the proton transfer reaction in this molecule.