Rene Dabard

Contribution a lietude des metallocenes : XII. acces, par echanges de ligands dans les derives du benzene chrome tricarbonyle, a des complexes organometalliques presentant un chrome asymetrique

Abstract Organometallic derivatives with a chiral centre at chromium were synthesized. The effect of substitution of one carbonyl by different ligands, and the extension to the case of disubstituted derivatives is discussed.

Contribution a l'etude des metallocenes—XXIII : Reactions d'echange de ligands entre les arenes et les derives ferroceniques comportant en α un ou deux substituants complexes par le chlorure d'aluminium☆

Abstract One or two unsaturated groups complexed by AlCl 3 and conjugated with the cyclopentadienyl(s) drastically change the nature of ligand exchange reactions of ferrocenes. The reactivity of ketone, aldehyde, alcohol, acid, ester and oxime groups has been examined; simple and double ligand exchange is shown to occur together with transformations of the functionnal groups, providing a route to new polynuclear cations.

Contribution to the study of metallocenes : XXIV. on the mechanism of ligand exchange and complexation by aluminium chloride of ferrocene and its alkylated and acylated derivatives

Abstract A mechanism of ligand exchange between ferrocene and arenes catalysed by AlCl3 is presented. It is shown how the attacking sites of AlCl3 depend on the electronic effect of substituents on the ferrocene rings. In ferrocene and its alkyl derivatives, two types of complexation occur and compete with each other: complexation of a ring reversibly leads to cleavage; irreversible complexation of the metal, possible only in the absence of electron-withdrawing substituents, inhibits metal—ligand cleavage.

The effect of replacing carbonyl groups by other ligands on the catalytic properties of arenechromium carbonyl complexes

Abstract The activities of a series of areneCr(CO) 2 L complexes in catalytic hydrogenation has been studied and found to be poorer than those of the Cr(CO) 3 analogs. The IR v (CO) changes of these complexes in THF have been shown to have value in predicting catalytic properties.

Etude structurale de ferrocenophanes I. Structure cristalline et moleculaire du (cyclopentylene-1″,3″)-1,1′ ferrocene

Abstract The crystal and molecular structure of 1,1-(1″,3″ -cyclopentylene)ferrocene, prepared by cleavage of ferrocene by AlCl3, has been determined by a single crystal X-ray study. The compound crystallizes with eight molecules in space group Pbca of the orthorhombic system in a cell of dimensions a 15.260(7), b 14.266(5), c 10.337(2) ». The observed and calculated densitie are 1.46 and 1.49 g cm−3. The structure has been solved by direct methods and refined by full matrix-least-squares methods to a final R index of 0.057. The dihedral angle between the best planes through the two planar cyclopentadienyl rings is 11° and is shown to be deduced from the length of the bridge. The cyclopentadienyl rings are eclipsed and the Fe—cyclopentadienyl distances are the same as in ferrocene. The cyclopentylene bridge is distorted and asymmetrical. The conformation is discussed with regard to 1H and 13C NMR results.

Contribution a l'etude des metallocenes : XXVIII. Reduction de cetones cycliques en series du ferrocene et du cymantrene. Etude de la stereospecificite. Assignation des configurations endo ou exo des alcools derives

Abstract The reduction of various 2,3-ferroceno-1-indanones and 1,2-(α-oxotetramethylene)-methylcymantrenes by metal hydrides or Grignard reagents is stereo-specific, except for LiAlH4, the observed stereoselectivity being in all uses more than 95%. The endo configuration of the dominant alcohol is established from TLC, IR, RMN and mass data. These criteria for the assignment of the structure of these alcohols are shown to be general.

Contribution a l'etude des metaux asymetriques III. Creation, en serie du cymantrene, d'une activite optique inherente a la chiralite du manganese

Abstract The photochemical substitution, by various phosphines or phosphites, of the carbonyl ligands of derivatives of cymantrene has been studied, giving evidence of the effect of the electron density on the metal for mono- or di-substitution. Optically active derivatives which are chiral at manganese have been synthesized and their enantiomeric stability ascertained.

Etude de l'hydrogenation de l'α-terpinene et du dihyro-2,3 anisole catalysee par le phenanthrene chrome tricarbonyle

Abstract The hydrogenation of α-terpinene and 2,3-dihydroanisole catalysed by phenanthrenechromium tricarbonyl in cyclohexane is described. The catalytic reaction is accelerated when small amounts of ketone are added to the solution. Attempts to induce asymmetric synthesis by adding (+)-3-menthylcyclohexanone or l-carvone to the reaction mixture are discussed. Isomerization of cis-Δ2-methene and α-phellandrene is also presented.

Réduction électrochimique de sels de cobalticinium

Abstract The polarographic behaviour of a series of mono- and disubstituted cobalticinium salts has been examined.

Etude structurale de ferrocenophanes ☆: II. Structure cristalline et moleculaire du bis-(cyclopentylene-1″, 3″)-(1,1′), (3,3′) ferrocene “syn”, C20H22Fe

The crystal and molecular structure of syn-bis(cyclopentyl-1″,3″-ene)-(1,1′),(3,3′)-ferrocenophane, produced by cleavage of ferrocene by AlCl3, has been determined by a single crystal X-ray study. The material crystallizes with four molecules in space group C2/c of the monoclinic system in a cell of dimensions: a = 20.119(5), b = 5.974(1), c = 14.456(9) », β = 125.47(2)°. The structure has been solved by Pattersons three dimensional method and refined by a full matrix least-squares method to a final R index of 0.059. The cyclopentadienyl rings of the ferrocene are shown to be significantly distorted from planitary and the cyclopentylene rings have a Cs conformation.