J. Levisalles

Structure radiocristallographique du veratrole-chrome-tricarbonyle; etudes RMN 1H d'arene-chrome-tricarbonyles ortho-disubstitues et regioselectivite de l'addition α-cyanocarbanion

Abstract The structure of veratroletricarbonylchromium in the solid state has been determined by X-ray study. The projection of the chromium atom on the arene plane is displaced by 0.06(1) A from the center of symmetry of the benzene ring toward the side opposite to the methoxy groups, and the conformation of the tripod is almost staggered with regard to the aromatic ring. Comparison between the 1 H NMR spectra of veratrole and veratroletricarbonylchromium shows that the protons ortho to the methoxy groups are less shielded during the complexation of veratrole with the Cr(CO) 3 entity and their chemical shift occurs at lower field. From these observations, it is deduced that there is a relationship between the chemical shifts of these protons and the regioselectivity of the addition to the aromatic ring of an α-cyanocarbanion. The same conclusion is extended to the case of other disubstituted arenetricarbonylchromium complexes.

Chimie organometallique: XXX. Etude par resonance magnetique nucleaire du proton et par radiocristallographie du N-methylindolechrome-tricarbonyle

Abstract The structure of N -methylindolechromium tricarbonyl ( 4 ) in the solid state has been determined by X-ray crystallography. The projection of the chromium atom on the N -methylindole plane does not coincide with the center of symmetry of the benzene ring; the tripod is distorted and the overall conformation of the complex is gauche rather than eclipsed. Study of the 1 H NMR spectrum of complex 4 in solution at +20°C and −38°C leads to similar conclusions. The results explain the nucleophilic attack at carbon atoms 4 and 7 of complex 4 .

Chimie organometallique : IX. Reaction du tungstadiphenylcarbene avec les ethers d'enols cycliques

Abstract Treating (CO)5Wue5fbC(Ph)Ph with cyclic enol ethers in n-hexane, leads, in the case of the cyclopentanone derivative, to ring-opened product (CO)5Wue5fbC(OEt)[(CH2)3CHue5fbC(Ph)Ph] which has been isolated and characterized. The ring size in the enol ether is the determining factor.

Metathese d'acetates d'alcools ω-insatures : Synthese de pheromones d'insectes

Abstract Esters of alkenoic acids, including insect pheromones as examples, have been synthesized using alkene metathesis reactions.

Chimie organometallique ☆: XV. Etude structurale d'un complexe dimetallique du tungstene portant a la fois un groupement μ-alkylidene et une double liaison coordinee a un des centres metalliques

Abstract The η-alkylidene complex CHCHCMe2[W(CO)4]2 gives, upon standing in solution at room temperature, a new complex CHCHCMe2[W2(CO)9] in which the double bond is coordinated to one of the metal centers. The possible participation of such complexes in olefin metathesis reactions is discussed.

Synthese de la meso-α,β bis(diamino-2,6 phenyl) octamethyl porphyrine

Abstract α,γ-Meso bis-(2,6-diaminophenyl) octamethyl porphyrin and derivatives have been prepared by an easy synthesis avoiding the separation of stereoisomers and represent a new kind of tetrafunctionalised porphyrin.

Chimie organometallique XIII. Preparation et determination structurale d'un complexe μ-alkyldene (octacarbonyle) ditungstenique (WW) ☆

Abstract The reaction of MeLi with MeOC(Me)W(CO) 5 (I) gives an unexpected binuclear complex [(CO) 4 W] 2 HCCHue5fbC(Me) 2 (II), the X-ray structure which shows a very short HCue5f8CH bond. A mechanism for the formation of II is outlined.

Chimie organometallique XIV. Homologation du methanol par des catalyseurs homogenes derives de cobalt

Abstract Selectivity for ethanol in the cobalt-catalysed methanol homologation reaction is increased by addition of borates and decreased by addition of hard cations. The influence of borates is assigned to an increase in carbenoid character of the intermediate acylcobalt, which should make hydrogenolysis easier.

Organo cyanocuprates: I. Formation et reactions avec les halogenures organiques☆

Abstract The formation of organocyanocuprates from organolithium compounds and cuprous cyanide is described, as well as their reactions with halides derived from alkanes, arenes and alkynes.

Recovery of chromium hexacarbonyl after nucleophilic reactions of arenechromium tricarbonyl complexes

Abstract The arenechromium tricarbonyl complexes C6H4R2Cr(CO)3, (R = H, CHMe2), obtained from arenes C6H4R2 and Cr(CO)6, react with nucleophiles (Nu = CH(CH3)CN, CH(CH3)CO2-t-Bu), to form adducts which give, after treatment with CF3CO2H under carbon monoxide, the substituted cyclohexadienes C6H5R2Nu (R = H, CHMe2) and Cr(CO)6 in good yield.