J. Satge

Synthèses et décomposition d'organométhoxygermanes et organométhoxyhalogénogermanes: Nouvelle méthode d'obtention de derivés organiques du germanium bivalent

Abstract The organomethoxy- and organomethoxyhalogermanes R2(MeO)GeH, R(MeO)GeH2, R(MeO)2GeH and R(MeO)(X)GeH (R = alkyl or phenyl) are synthesized by direct reaction at low temperature of sodium or lithium methoxides with the organohalogermanes R2(X)GeH, R(X)GeH2 and R(X)2GeH and by “chlorinemethoxy” exchange reactions between the same halohydrides and various methoxyorganogermanes. The instability of the organomethoxygermanes with GeH and GeO bonds lead to their decomposition with formation of divalent species of germanium and methanol. The “germylenes” 1 were characterized by condensation on the insaturated systems of 1,3-dienes and also by insertion into some σ-bonds.

DIFLUORENYL- AND TERT-BUTYLFLUORENYL(FLUORENYLIDENE)GERMENES : SYNTHESIS, STABILISATION AND FIRST ASPECTS OF THEIR REACTIVITY

Abstract Two new stable compounds with a germaniumcarbon double bond, the difluorenyl(fluorenylidene) germene 5 and the tert-butylfluorenyl(fluorenylidene)germene 11 have been synthesized by dehydrohalogenation of the corresponding halogenogermanes with tert-butyllithium. These germenes are stabilized both by steric effects of bulky groups such as fluoroenyl or tert-butyl and by delocalization of electrons into the fluorene system.

STABLE METALLA-ALKENES >M=C M=M< (M : Si, Ge, Sn)

The synthesis of doubly-bonded species of group 14 elements such as metalla-alkenes >M=C< and dimetalla-alkenes >M=M< (M : Si, Ge, Sn) has been during a long time a great challenge for organometallic synthetic chemists. Since the isolation, in 1981, of the first stable silene by Brook [1] and disilene by West [2], exciting progress has been made in this field and now many species which were thought to exist only as intermediates have been prepared and isolated. The previous reviews published in this field (silicon [3-12], germanium [12-17] and tin [14]) were generally devoted to only one group 14 element or to one type of doubly-bonded species (>M=C< or>M=M<). Thus, the purpose of this paper is to collect in a sole short review, presented in the form of tables and with brief comments, the information on the synthesis and the characteristic physicochemical data (Si, Sn NMR, double bond lengths) of all the doubly-bonded silicon, germanium and tin derivatives of the type metalla-alkenes >M=C< and dimetalla-alkenes >M=M< prepared until the end of 1995. The synthetic routes to these derivatives are summarized in schemes. As the synthesis and the reactivity of transient species of this type are particularly well documented, we will limit our study to stable derivatives or to derivatives at least characterized by physicochemical methods such as NMR or UV. The reactivity of such compounds is not reviewed in this paper.

Réactivité des dialcoyl(trialcoylgermyl)phosphines avec divers dérivés carbonylés

Abstract Aldehydes condense on the germaniumphosphorus bond of diethyl(triethylgermyl)phosphine with opening of the CO double bond and formation of phosphorus alkoxygermanes of the structure GeOCHP. The insertion derivatives of chloral and bromal are unstable and decompose via a β-elimination process. The addition of dialkylketones is far more difficult and only the ketones with a little hindered carbonyl group, such as cyclopentanone, or those activated by electron-attracting groups, such as hexafluoro-, hexachloroacetone, 1,1,3,3-tetrafluoro-1,3-dichloro- or 1,3,3-trifluoro-1,1,3-trichloropropanone lead to insertion derivatives which are not very stable [with the exception of (CF 3 ) 2 CO], which have been characterized by their transposition, decomposition, oxidation or hydrolysis products. α-Ethylenic aldehydes and ketones such as crotonaldehyde, cinnamaldehyde and 2-cyclopentene- 1 -one give 1,4-dipolar additions on their conjugated system, with formation of phosphorus enoxygermanes; hydrolysis of these derivatives leads to γ-phosphorus aldehydes or ketones. An addition mechanism involving an ionic cleavage of the germaniumphosphorus bond is considered. Ketenes insert in the germaniumphosphorus bond through an exclusive opening of the carbonyl group. Hydrolysis of the phosphorus enoxygermanes which are thus formed leads to “α-phosphoryl-ketones” which are also isolated by the action of germylphosphines on acid anhydrides.

A new stable germaphosphene and some of its chemical properties

Abstract A new stable germaphosphene, the 2,2-dimesityl-1-(2,4,6-triipropylphenyl)germaphosphene ( 1 ), has been made. It reacts quantitatively with benzaldehyde and α-phenyl- N -tert-butylnitrone to afford, by [2+2]- and [2+3]-cycoloadditions, respectively, the correponding four- and five-membered heterocycles 10 and 13 . The conformations of these heterocycles are discussed. The reactions of 1 and 2,2-dimensityl-1-(2,4,6-tri-tert-butyphenyl) germaphosphene ( 2 ) with these reagents are compared.

Intermédiaires organiques du germanium divalent I. Synthèse de germanes α ou β fonctionnels par insertion de germylenes sur les liaisons C-X de dérivés organiques halogénés

Abstract The organic derivatives of divalent germanium (germylenes) of the type: R(Cl)Ge:(R=alkyl, phenyl, chlorine) obtained by decomposition at room temperature of the methoxychlorohydrogermane R(Cl)(MeO)GeH, were condensed on various organic halo derivatives. The insertion of the germylenes on the halogen-carbon bond of β-ethylenic halo-compounds, α-haloketo derivatives, acid chloride or α-haloethers, leads to the formation of functionally substituted α or β organopolyhalogermanes some of which can not be prepared by other ways. These insertion derivatives can be characterized by NMR and IR spectroscopy, as well as by chemical route. In some cases, the functional germanes isolated by reduction or alkylation of the insertion products have been synthesized independently by new chemicals ways.

Thermolyse et photolyse d'heterocycles a liaison GeS. Mise en evidence de la formation de germylenes et germathiones

The photolysis and thermolysis of 2,3-digerma-1,4-dithianes, 2,3,5-trigerma-1,4-dithiolanes and tetragerma-1,4-dithianes have been studied. 2,2,3,3-Tetramethyl-2,3-digerma-1,4-dithiane (I) decomposes slowly at room temperature by α-elimination to yield dimethylgermylene (Me2Ge:) and 2,2-dimethyl-2-germa-1,3-dithiolane (II). 2,2,3,3,4,4-Hexamethyl-2,3,4-trigerma-1,5-dithiepane (III) is obtained by the insertion of Me2Ge: into the sulfur-germanium bond of I. At 200°C, I undergoes thermal fragmentation leading to II, III and 2,2,3,3,5,5-hexamethyl-2,3,5-trigerma-1,4-dithiolane. These results are explained by two concurrent mechanisms of decomposition of I, involving formation of dimethylgermylene (Me2Ge:) and dimethylgermathione (Me2GeS), respectively. Photolysis of I or 2,2,3,3,5,5,6,6-octamethyl-2,3,5,6-tetragerma-1,4-dithiane and thermolysis of the latter heterocycle generate dimethylgermylene and heterocycles resulting from dimethylgermylene expulsion. 2,2,3,3,5,5-Hexamethyl-2,3,5-trigerma-1,4-dithiolane is thermally and photochemically stable.

First characterization of a compound with a tin–germanium double bond: the dimesityl(diisitylstanna)germene (Is)2SnGe(Mes)2

The dimesityl(diisitylstanna)germene 4 [isityl (Is)= 2,4,6-triisopropylphenyl] is synthesized by dehydrofluorination of the corresponding (fluorostannyl)germane 1 by tert-butyl-lithium at low temperature; its structure is evidenced at –20 °C by 119Sn NMR spectroscopy (δ+ 360), by addition of water and methanol to the tin–germanium double bond and by a [2 + 2] cycloaddition with benzaldehyde; warming the stannagermene 4 to room temperature affords the dimesityl(tetraisityldistanna)germirane 8.

Nouveaux intermediaires du germanium π-lie: les germaphosphimines

Abstract The formation of new π-bonded germanium intermediates with dicoordinated phosphorus atoms, germaphosphimines [R 2 2GePR′], has been observed in the exchange reaction between 2,5-disilaphospholanes and dialkyldihalogenogermanes. These transient species have been clearly characterized by insertion and ring expansion reactions on ethylene oxide and sulfide with formation of new heterocycles 2-germa-3-oxyphospholanes and 2-germa-3-thiophospholanes.

Dibisyl(fluorenylidene)stannene: evidence of its formation

Abstract The dibisyl(flourenylidene)stannene 4 , obtained by dehydro-chlorination or -fluorination of the corresponding chloro- or fluoro-stannanes 5 and 6 by tert-butyllithium is an extremely air-sensitive compound. It has not been isolated, but identified by trapping reactions by lithio compound and water.