G. Jaouen

Synthese directe de composes areniques bis-chrome tricarbonyles

Abstract Heating of Cr(CO)6 and a polyaromatic compound in a mixture of dibutyl ether and THF (90/10 v/v) under reflux (in an inert atmosphere) allows the direct dicomplexation of the polyaromatic in good yield. The scope, limitations and advantages of the method are discussed.

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.

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.

Synthesis of the pentacarbonyl(chalcocarbonyl)chromium(0) complexes, Cr(CO)5(CX) (X = S, Se)

Abstract The arene complexes, (η 6 -C 6 H 6 )Cr(CO) 2 (CX) (X = S, Se), react with excess CO gas under pressure in tetrahydrofuran at about 60° C to produce the Cr(CO) 5 (CX) complexes in high yield. The IR and NMR ( 13 C and 17 O) spectra of these complexes are in complete accord with the expected C 4 v molecular symmetry. Like the analogous W(CO) 5 (CS) complex, both compounds react with cyclohexylamine to give Cr(CO) 5 (CNC 6 H 11 ). However, while W(CO) 5 (CS) undergoes stereospecific CO substitution with halide ions (Y − to form trans -[W(CO) 4 (CS)Y] − , the two chromium chalcocarbonyl complexes apparently undergo both CO and CX substitution to afford mixtures of [Cr(CO) 5 Y] − and trans -[Cr(CO) 4 (CX)Y] − .

Contribution a l'etude des metaux asymetriques—II : Voie d'acces aux premiers complexes pseudo tetraedriques du chrome (0) enantiomeriquement stables

Abstract Modes of access to several pseudo tetrahedral complexes having an asymmetric chromium atom are presented. The chirality at the metal atom is demonstrated by NMR. The first enantiomers of chiral chromium (0) are obtained in optically pure forms.

Les ions α-carbéniums benchrotréniques: mode de génération, exemples d'utilisation a la préparation d'amines, d'éthers et au contrôle stéréochimique lors d'attaques nucléophiles

Abstract Temporary complexation of benzylic alcohols by the Cr(CO) 3 unit considerably enhances the stability of the carbenium ions generated from these alcohols and allows the preparation of amines, ethers by reaction of the ions with ammonia, amines or alcohols. This method also permits the total stereochemical control in the “ exo ” position of nucleophilic attack in the rigid series (indane, tetraline) and thus giving rise to “ exo ”-tricarbonyl chromium-1-indanol or -1-tetralol. Stereochemical studies of open chain compounds show retention of configuration.

Stereoselective nucleophilic attacks on carbenium ions generated from (1-indanol)- and (1-tetralol)Cr(CO)3 as synthetic intermediates.

Abstract Temporary complexation of an arene ring by the Cr(CO) 3 unit bringing about both a considerably enhanced stabilization of adjacent carbenium ions and a total control of nucleophilic attack in an “exo” fashion allows important applications in organic synthesis.

Preparation et etude des proprietes electroniques et chimiques de ligands isocyanures fonctionnels cncor coordines au chrome et au manganese

Abstract A series of various functionalised isocyanide ligands CNCOR (R = C 6 H 5 ,N(CH 3 ) 2 , OC 2 H 5 , SC 2 H 5 ) has been prepared as chromium and manganese complexes. The IR and mass spectroscopic studies show that the presence of carbonyl function in the α position to the nitrogen results in the ligand being a better electron acceptor than CO. The strengthening of the metal-carbon bond, with respect to M  CO, allows access to centro-chiral complexes, but also results in a more labile chromium-arene bond, this gives a new synthetic route to Cr(CO) 5 (CNCOC 6 H 5 ).

Influence des substituants sur l'activite catalytique des composes arene-chrome tricarbonyle, mise en evidence de l'imfortance d'un α-heteroatome (O, N)

Abstract Substituents bearing a heteroatom in α position to an Cr(CO) 3 -complexed arene group induce a strong perturbation in the six-electron ligand—metal bond allowing an increased catalytic effiency of these derivatives under mild conditions.

Facile Cr(CO)3 exchange between arenic ligands as a new method for the synthesis of benchrotrenic compounds

Abstract Tertiary alcohols derived from benzenetricarbonylchromium are used as a source of Cr(CO)3 unit; this reaction allows direct synthesis of compounds bearing various functional groups but no asymmetric induction occurs in the exchange.