H. Ranaivonjatovo

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.

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.

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.

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

STABLE MULTIPLY-BONDED GERMANIUM AND TIN SPECIES

Several stable metallaalkenes ^M=Cand metallaphosphenes -M=P(M : Ge, Sn) have been synthesized since 1985, mainly by reaction of tert-butyllithium with halogenometallaalkanes or halogenometallaphosphines. Some examples of their high reactivity, particularly toward protic reagents and carbonyl compounds (aldehydes, ketones, α,β-ethylenic aldehydes), as well as their thermolysis and dimerization, are described, and compared to the chemical behaviour of other doubly-bonded main group elements. The syntheses of new types of multiply-bonded species are discussed.

FROM SILYLPHOSPHANES AND 2-BENZAL-1-INDANONES TO NEW PHOSPHANES, PHOSPHANE OXIDES OR SULFIDES AND PHOSPHONIUM SALTS

Abstract Diethyl(trimethylsilyl)phosphane 1 reacts with the conjugated carbonyl moiety of 2-benzal-1-indanones 2–6 to afford exclusively 1,4-adducts 2a–6a. Subsequent oxydation or sulfuration of most of the adducts leads to the corresponding phosphane oxides or sulfides. Further hydrolysis or reaction with HCl involves the desilylation with the formation of new (thio)phosphorylated ketones or phosphonium salts.

REACTION OF STANNENES AND PHOSPHASTANNENES WITH ALDEHYDES AND KETONES: NEW TIN FOUR-MEMBERED RING DERIVATIVES

Stannene Tip2Sn=CR21 (Tip=2,4,6-triisopropylphenyl, CR2=fluorenylidene) enters a [2+2] cycloaddition reaction with benzophenone to afford the four-membered ring derivative2. This stannaoxetane undergoes a [2+2] decomposition with formation of the corresponding stannanone8 and alkene9 and an easy hydrolysis by initial cleavage of the Sn−C bond. Diphenylacetaldehyde also gives with1 a stannaoxetane, which has been characterized by its hydrolysis products. Phosphastannene Tip2Sn=PAr13 (Ar=2,4,6-tri-tert-butylphenyl) reacts with benzaldehyde according to a [2+2] cycloaddition pattern leading to stannaphosphaoxetane14, whereas ene-products19–21 were obtained with acetaldehyde, acetone, and acetophenone.

From Silylphosphanes and Oxazolones to New Phosphorus Amido-Acids

Silylphosphanes 3 and 4 gave 1,4-additions with the O=C-C=C moiety of oxazolones 1a-e and 2a-f to afford the adducts 5–8. Oxidation or sulfuration of 5–8 followed by hydrolysis led to oxyphosphorus (or thiophosphorus) amido-acids 9–11 and 15, 19, 20 respectively. A great difference was observed in the behaviour of thiophosphane oxides 16 (R = Me) and 17(R = Ph) toward hydrolysis: 16 led directly to the amido-acid 19 by opening of the lactonic ring whereas, from 17, the heterocyclic intermediate 18 could be isolated.