Gabriel Dousse

Germanones ET germathiones: Réactivité vis-à-vis de petits cycles organiques

Dialcoylgermanones and dialcoylgermathiones are generated from various germa-heterocyclic precursors and dimeric or trimeric forms (R2GeO)2 and (R2GeS)3. These species [R2GeS] (X = O, S) react with various three- or four-membered rings (n = 2, Y = O, S, NR, CHCN; n = 3, Y = O, S) to lead to the germaheterocycles (X = O, S). Cyclogermathianes (R2GeS)3 lead very easily, by thermic and catalytic dissociation to the germathiones [R2GeS]. Basic solvents (Et3 N, HMPA) and catalysts [(Ph3P)2 PdCl2] induce these dissociations. Mechanism and stereochemistry of insertion reactions of these transient species [R2GeX] (X = O, S) into oxirane rings are established from cis- and trans-butene oxides. The formation of germanium hexacoordinated intermediate complex can explain the observed stereoselectivity. With germathiones the stereoselectivity derives from the strong nucleophilic activity of these species.

La Diethylgermathione Et2GeS: formation et caracterisation

Resume The adducts of some germaoxazolidines and germadiazolidines with CS2 or PhNCS give by β-elimination reactions transient dialkylgermathione, R2GeS, which is characterized by addition on the germanium—sulfur bond of Et3GeSMe and by insertion and ring expansion reactions with ethylene oxide or thiirane and formation of germaoxathiolane or germadithiolane. The equilibrium between monomeric (Et2GeS) and trimeric species (Et2GeS)3 is established. The desulfuration reaction of germadithiolane by tributylphosphine leads to germathione probably via transient germathlacyclobutane.

Reactions de germylenes avec des heterocycles a trois chainons. Mise en evidence d'especes tricoordinees du germanium R2Ge=X (X = O, S) et de nouveaux germylenes fonctionnels

Abstract Condensations of complexed dialkylgermylenes R 2 Ge · NEt 3 with various oxiranes and thiirane gave, by insertion and ring expansion, the corresponding oxa- and thia-germacyclobutanes . These thermally unstable heterocycles led via β-eliminations to transient dialkylgermanones and germathiones which, by insertion into oxirane and thiirane (excess) formed germadioxolanes and germadithiolanes. Dialkylgermylenes did not react with N -substituted aziridine. Dichlorogermylene reacted with aziridine under formation of aziridinogermylene, while it formed complexes with N -ethylaziridine. Cleavages of aminogermylenes and insertion reactions of complexed dichlorogermylene are described. Dialkylgermylenes insert into the OH bond of methanol leading to dialkylmethoxygermanes R 2 Ge(H)OMe.

Action des derives du phosphore tricoordonne sur les germanones et germathiones: Oxydation des phosphines

Abstract Desulfuration reactions of germadithiolanes by trialkylphosphines lead to germathiones via intermediate germathietanes. The formation of germylenes finally observed arises from reduction of germathiones by trialkylphosphines. Analogous reduction reactions of germanones by three coordinated linear and cyclic phosphorus compounds are also described.

Action De Divers Agents Oxydants Sur Les Germylenes

Abstract Oxidation reactions of germylenes by various oxidizing agents (O2, MnO4K, DMSO, C5H5NO, p.NO2C6H4COOOH) give derivatives of the type (X, Y : halogens, alkyl, phenyl),which polymerize to the corresponding germoxanes . XYGe=O intermediates have been characterized by addition to ethylene oxide, methoxygermane R3GeOMe and condensation reactions with excess of germylene and the formation of germoxanes with Ge-Ge bonds: .

Physical-chemical studies and reactivity of new divalent germanium species

Abstract This work concerns the synthesis of five- and six membered ring heterocyclic germlenes, derived from hydroxy or thiohydroxy acids and germanium spiranic corresponding structures. These compounds were prepared by the exchange reaction of dichlorogermylene and germanium tetrachloride with different germanium heterocycle compounds Ge(IV). Structural studies (IR, 13 C NMR) of 11–17 revealed that these derivatives, which show a double or triple mass peak spectroscopy, are intermoleculary associated by the carbonyl group to the metal CO| → Ge. However, different cycloaddition reactions with dienes, quiones and heterobutadienes showed these dimers or timers had a germylene type reactivity. Oxidation reactions of germylenes 10 and 12 are also described.

Intermediaires organiques du germanium divalent: II. Reactions d'insertion de germylenes sur diverses liaisons germanium-heteroelement. nouvelle synthese de phenylgermylenes fonctionnels

Abstract Some digermanes which are able to generate functional germylenes PhGeY (Y = MeO, MeS, Me 2 N, Et 2 P) are obtained in insertion reactions of phenylhalogermylenes in germaniumheteroelement bonds (O, S, N, P) in the derivatives R 3 GeY. This reaction, corresponding to a substitution of the halogen by the Y group, proceeds by formation of a digermane which is stable at room temperature, but decomposes under heating, giving the divalent species PhGeY. These divalent species PhGeY (Y = MeO, MeS, Me 2 N) react very easily with GeCl and GeO bonds and their insertion reactions are reversible. In the reaction between PhGeCl and Et 3 GeH, only reduction with formation of (PhGeH) η has been observed.

Generation of dimethylgermathione and dimethylsilathione and their detection in the gas phase by photo-electron spectroscopy

Abstract We report in this paper the first spectroscopic detection (photoelectron spectroscopy) of germathiones and silathiones, which previously had been characterized only by chemical trapping [1].

Syntheses de Phenylalcoxy et Phenylalcoylthio- Germanes et Polygermanes par Reactions D'Echange

Abstract The use of exchange reactions Ge-X/Ge-Y (X = halogen; Y = MeO, MeS) between phenylhalogermanes or polygermanes and functional trialkylgermanes may give selectively and quantitatively various substituted phenylgermanes and polygermanes. These reactions are readily adapted to the synthesis of X2(Y)GeH, Ph(X)(Y)GeH, PhY2GeGeY2Ph, (PhY2Ge)2Ge(Y)Ph, (PhY2Ge)3GePh derivatives which may not be obtained by direct action of organometallic compounds YM (M = Li, Na, MgX) in basic solvents. Germanium-hydrogen bonds also give similar exchange reactions of the Ge-H/Ge-Y type; but these latter reactions probably are of the radical type and always lead to equilibria.

Nouvelles espèces divalentes du germanium

Abstract New organogermanium(II) intermediates are characterised from various acyclic and cyclic alkoxyhalogermanes after tributylstannane reduction and α-elimination on the germanium.