Jean-Louis Piette

Structure cristalline et moléculaire du bromure d'o-formyl phénylsélényle (C7H5OSeBr)

The crystal and molecular structure of o-formylphenyltellurenyl bromide has been determined by three-dimensional X-ray analysis. Crystals are monoclinic (P21/c) and the unit cell has the dimensions a = 12.533, b = 5.839, c = 11.706 A and β = 102.48°. The refinement of the structure by Fourier and block-diagonal matrix least-squares methods has led to a final R value of 0 081. The molecule has a planar cis configuration. The coordination of the Te(II) atom is described with the model proposed by Foss. The existence of a Te-O bond is discussed.

N.M.R. and conformational analysis of some Te-containing ortho-substituted benzaldehydes

We report the analysis of the high-resolution proton magnetic resonance spectra of some 2-halotellurenyl-benzaldehydes (Cl, Br, I) and of 2-methyltellurobenzaldehyde, considered as ABCD spin systems. The identification of the long-range couplings in these molecules shows that they all have a ‘cis’ conformation of the aldehyde carbonyl relative to the ortho-substituent. An electronic model which explains this conformation in the case of the haloderivatives is suggested. It agrees with infra-red measurements. In the case of the methylated compound, another model is proposed to account for our observations, in agreement with the results reported by Andrieu and Ruwet for 2-methoxy, 2-methylthio- and 2-methylselenobenzaldehyde. We observed coupling of the methyl protons with the nuclei 123Te (27·0 Hz) and 125Te (32·5 Hz) in 2-methyltellurobenzaldehyde.

Etude par RMN de composés organiques contenant des chalcogènes—VIII. RMN du 13C dans la chromannone, la chromone, la coumarannone-3 et la coumarine et leurs analogues soufrés, séléniś et tellurés

Abstract 13 C NMR spectra of the title compounds have been fully assigned. The results have been compared with those relative to other chalcogenated compounds, such as anisole, phenyl benzoate, benzofuran,… and their analogs. In chalcogenochromones and -coumarines, the heteroatom lone pair delocalization spreads to some extent over the heterocyclic part of the molecules, while in chalcogenochromanones and -indoxyles, it only extends to the homocycle. This electronic effect seems also to affect the heavy atom effect exhibited by Te-containing compounds.

Résonance magnétique nucléaire du sélénium-77 dans des sélénolesters

Abstract We report the selenium 77 chemical shifts in twenty selenolesters R 1 -C(O)-Se-R 2 . The δ( 77 SE) variations with the nature of R 1 and R 2 are discussed within the scope of the resonance interactions between selenium and carbonyl. The most important form in the selenolesters studied seems to be:

Synthèse et études spectroscopiques des tellurolesters

Abstract A general procedure for Te-alkylated tellurolesters synthesis is reported. The carbonyl i.r. frequencies and 13 C chemical shifts of these compounds are compared to the O, S and Se analogs. The origin of the electronic interaction between the carbonyl group and the heteroatom is shown to depend on this latter nature: whereas a combination of both inductive and mesomeric effects is to be taken into account for O. This effect is mainly inductive for Se and Te. In the case of S-compounds, no such a simple model can be involved. The reason of which might be the participation of the 3d-orbitals to the electronic system. Moreover, the previously reported Te heavy atom effect has been detected on the α methylene groups exclusively.

Un abaissement important de la fréquence infra-rouge du carbonyle des dérives aromatiques substitutês en ortho par les groupements SeCl, SCl et SeCN

Abstract The frequency of the aromatic carbonyl group undergoes an important and systematic lowering when this group is fixed in ortho position of a substituent as SeCN, SeSPh, SCl, SeCl or SeBr. The interpretation of this phenomenon is discussed and attributed to a field-effect between the selenium positively polarized by induction through the electronegative substituent it is carrying, and the oxygen of the carbonyl. This effect stabilizes the cis -form, usually still more stable by steric effect; hence, the phenomenon of rotational isomerism is very rarely observed in these derivates. The intensity of the effect is discussed in function of the nature of the carbonyl and the ortho -substituent.

Etude par RMN de composés organiques contenant des chalcogénes—VI. Résonance magnétique du carbone 13 dans les acétates et benzoates de n-butyle et de phényle et dans leurs analogues soufrés, séléniés et tellurés☆

Abstract A study by 13 C NMR of some esters and their chalcogen analogs is presented: R 1 C(O)XR 2 , (X  O, S, Se, Te), (R 1 , R 2  alk, ar). The chemical shifts are discussed in the scope of the mutual interaction between R 1 and R 2 through the carbonyl group and through the heteroatom. The results are in agreement with a recent study by 77 Se NMR of the selenolesters: they confirm the importance of the resonance form in these type of compounds.

Etude en spectrographie i.r. de la vibration carbonyle des tellurolesters aryliques

Resume We have studied by i.r. spectroscopy the position of the carbonyl band of various tellurolesters. We have seen a splitting of the v C0 band, attributed to a Fermi resonance. This assignment is supported by solvent and temperature effects.

Etude par RMN de composés organiques contenant des chalcogènes. IX: RMN du 13C dans des dérivés aromatiques du tellurényle

Abstract In order to synthesize new tellurium heterocycles, we prepared o -halogenotellurobenzoyl chlorides. We present and discuss here the results of a 13 C NMR study of these compounds, together with other intermediates that we have isolated during our synthesis and two new tellurium heterocycles.

Etude par resonance magnetique nucleaire de composes organiques contenant des chalcogenes: Partie IV. Le disulfure de diphényle et ses analogues sélénié et telluré

Abstract NMR measurements ( 1 H, 13 C, 77 Se) of diphenyl dichalcogenides are reported. They confirm the molecular conformation deduced from other physical experiments. Steric inhibitions are responsible for the conformation in the Te compound, while, in the S and Se compounds, the heteroatom lone pairs interact to some extent with the π systems of the rings. More fundamental discussions of the measured parameters are made, including the somewhat controversial existence of the title compounds in solution.