J. Escudie

Le premier diarsene stable : le bis[tris(trimethylsilyl)methyl diarsene

Abstract The first stable diarsene (Me 3 Si) 3 C-As=As-C(SiMe 3 ) 3 has been synthesized and characterized by its physico-chemical data. Addition of sulphur leads to the first diarsathiiran.

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

Abstract Two new stable compounds with a germaniumue5f8carbon 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.

Réactivité des dialcoyl(trialcoylgermyl)phosphines avec divers dérivés carbonylés

Abstract Aldehydes condense on the germaniumue5f8phosphorus bond of diethyl(triethylgermyl)phosphine with opening of the Cue5fbO double bond and formation of phosphorus alkoxygermanes of the structure ue5fcGeue5f8Oue5f8CHue5f8Pue5fb. 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 Cue5fbO], 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 germaniumue5f8phosphorus bond is considered. Ketenes insert in the germaniumue5f8phosphorus 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.

BIS[TRIS(TRIMETHYLSILYL)METHYL] DIPHOSPHENE STRUCTURE ET REACTIVITE

Abstract Some aspects of the reactivity of disphosphene RP[dbnd]PR 1 (R [dbnd] (Me3Si)3C) are described, particularly reduction (LiAlH4), electrophilic additions (HCl, Cl2), heterocyclisation reactions (S8). The very bulky (Me3 Si)3C group well stabilizes the adducts RP(H)P(H)R 5, RP(H)P(Cl)R 6, RP(H)Cl 7, RP(Cl)P(Cl)R 8, 11 such compounds being often unstable. Structure of 1 was determined by single crystal X-ray diffraction. 1 crystallizes in the triclinic space group; two independent centro-symmetric molecules are present in the unit cell, one of them shows a disorder at the level of silicon atoms; the P[dbnd]P bond lengths are respectively 2.003(3) and 2.001(3) A. Data are listed in Tables I to IV. All other crystallographic data are deposited with the Cambridge Crystallographic Data Centre (CCDC). Quelques aspects de la reactivite du diphosphene RP[dbnd]PR 1 (R [dbnd] (Me3Si)3C) sont presentes, en particulier des reactions de reduction (LiAlH4), dadditions electrophiles (HCl, Cl2) et dheterocyclisa...

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 2Geue5fbPR′], 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.

METALLAIMINES >M=N-, METALLAPHOSPHENES >M=P- AND METALLAARSENES >M=As-

All the stable metallaimines >M=N-, metallaphosphenes >M=Pand metallaarsenes >M=As(M: Si, Ge, Sn) prepared until now are reported with their synthetic routes and their characteristic physicochemical data (Si, 3 P, 1 1 Sn NMR, double bond lengths). The routes to transient species are also summarized. Introduction Many researches have been devoted to low coordinated species of groups 14 and 15 in the last 30 years. However, in the field of compounds with a double bond between two heavy elements of these groups, thus derivatives of the type >M-|4=Mi5(M14: Si, Ge, Sn; M15: Ν, P, As), it is only in 1984 that the first stable example of such new organometallic functions, the phosphasilene Mes2Si=PAr [1] (Ar: 2,4,6-tri-tert-butylphenyl), has been reported by Bickelhaupt. Since this date, many other >Mi4=M-|5derivatives have been successfully synthesized, and some of them stabilized owing to the use of bulky groups which prevent their oligomerisation (for reviews on Si=X see ref 2-4, on Ge=X see ref 4-6). The main purpose of this review is to report in schemes, with only very brief comments, all the possible routes to such transient or stable compounds, and to present in the form of tables all the stable derivatives prepared until now with their characteristic physicochemical data (Si, 3 P, 1 1 9 Sn NMR, double bond lengths). The reactivity of these species is not reviewed in this paper. I TRANSIENT METALLAIMINES a) Silaimines Many reactions have been described for the synthesis of transient silaimines. These species have only been characterized by trapping. The next scheme summarizes all the routes to these derivatives. Many of these reactions have already been reported in the very well documented review by G. Raabe and J. Michl [2], Thus, in this paper, we give only the references corresponding to the papers published after this review. (1) Curtius rearrangement with loss of nitrogen [2, 7-12]. (2) thermal decomposition of a silaazetidine [13-14]. (3) reaction of an alkyllithium with a halogenosilylamine, and elimination of LiX [2, 15]. (4) reaction of an alkyllithium with a silylamine, followed by addition of chlorosilane in non polar solvents producing cyclodisilazanes via a silaimine intermediate [16, 17], (5) thermal elimination of trimethyl(methoxy)silane [2]. (6) thermal elimination of imine from a siladiazetidine [2]. (7) reaction of an azide with a transient silene leading to a silatriazole followed by a [2+3] decomposition [18, 19]. (8) intermolecular dehydrochlorination between a dichlorosilane and a primary amine by an excess of amine [20]. (9) elimination of propene from a hydrosilyl(allyl)amine by a retro-ene reaction [21], (10) reaction of a silylazide with a transient silylene, with intermediate formation of a silatriazetidine

METALLA IVb-PHOSPHOLANNES I. Dimetalla-2,5 Phospholannes, Metalla-2 Diphospholannes-1,3 et Metalla-3 Diphospholannes-1,2

Abstract We present the synthesis of novel sila-, germa- and stanna-phospholanes: 2,5-dimetallaphospholanes, 2-metalla 1,3-diphospholanes and 3-metalla 1,2-diphospholanes. Preparation and characterization reactions of the first stable diphosphorus germylene are also described. Nous decrivons dans ce memoire la synthese de nouveaux sila- germa- et stannaphospholannes: dimetalla-2,5 phospholannes, metalla-2 diphospholannes-1,3 et metalla-3 diphospholannes-1,2. Nous exposons egalement la preparation et les reactions de caracterisation du premier germylene diphosphore stable.