Pierre Gerval

Mise en evidence de la formation de R2MMR2 a partir de disila-1,2 et digerma-1,2 cyclohexenes-4

Abstract Intermediates with π-bonded Si or Ge are generated during gas phase pyrolysis of 1,2-disila- or 1,2-digerma-cyclohex-4-enes. Compounds such as R2MMR2 are successfully trapped by addition or [2 + 2] and [4 + 2] cycloadditions. These results were proved by mass spectrometry.

Spectres de vibration de composes organiques des elements de la colonne IV B : XII - Organopolygermanes☆

Abstract An investigation and interpretation is presented of the infra-red and Raman vibrational spectra of sixteen organic compounds with a GeGe bond. Some compounds of these series were specifically synthesized for this study. An assignment can be given to most observed bands. Particular attention is given to the discussion of the position of vibration frequencies υ(GeGe) and υ(GeH). From a comparison of the υ(SiH) and υ(GeH) frequencies it may be stated that the (p → d) π and (d-d) π interactions which can occur in some compounds are weaker in the case of digermanes than for disilanes.

Spectres de vibration de composes organiques des elements de la colonne IVB : VI. Comparaison des frequences de vibration observees sur des derives oxygenes cyclopentaniques et cyclopenteniques du silicium, du germanium et de l'etain et comparaison de leur basicite☆

Abstract The characteristic vibrations in IR and Raman spectra of 1-oxa-2-sila- (2-germa- or 2-stanna-)cyclopentanes and 1-oxa-2-germa- (or 2-stanna-)-3-cyclopentenes are compared. The basicity of the oxygen of these compounds is determined by IR measurements.

Spectres de vibration de composes organiques des elements de la colonne IVb: XIII. Etude physico-chimique par spectrometries rmn, infrarogue et raman de disila-1,2 et digerma-1,2 cyclohexenes-4 et digerma-1,2 cycloalcanes☆

Abstract 13 C, 29 Si NMR, infrared, Raman and UV spectra of a series of 1,2-disila- and 1,2-digerma-cyclohex-4-enes and 1,2-digermacycloalkanes with 5-, 6- and 7-membered rings are studied. The results of these studies can he compared with those of 1-sila- and 1-germa-cyclopent-3-enes previously studied. Such a comparlzon shows that the ring strain in disila- and digerma-cyclohexenes is very weak and that their non planar structure results in a σ(CH 2 —M)—π(CC) conjugation and a double “β effect”.

Spectres de vibration de composes organiques des elements de la colonne IVB : V. Derives cycliques oxygenes du silicium et de l'etain: Oxa-1 sila-2 cyclopentanes, oxa-1 stanna-2 cyclopentanes et cyclopentenes☆

Abstract Infrared and Raman spectra of two 1-oxa-2-stannacyclopentanes, three 1-oxa-2-stannacyclopentenes and three 1-oxa-2-silacyclopentanes have been examined in the 3600—100 cm−1 region. Assignments of the main bands observed are discussed.

Fréquences infrarouges et Raman caractéristiques de triméthylsilyl-et chloro-bicyclo (n, 1, 0) alcènes: Relations avec la structure—II☆

Abstract Infrared and Raman spectra of bicyclo ( n , 1, 0) alkenes with one or two trimethylsilyl groups and of α-chlorosilicon compounds are recorded and interpreted. Results show that the position of silyl groups is very important for the Raman spectra pattern of monosilyl compounds and allow the determination of the geometry (“endo” or “exo” isomers). The ν(CC) frequency values enabled us to demonstrate that, according to the position of the double bond, a conjugation between the cyclopropane and the double bond may occur for six and seven membered cycles.

Silicon-Assisted Ethoxycarbonylmethylation ofN-Methylquinolinium and Isoquinolinium Iodides

A new regioselective route to 2-ethoxycarbonylmethyl-1,2-dihydro-N-methylquinolines and 1-ethoxycarbonylmethyl-1,2-dihydro-N-methylisoquinolines is described starting from methylquinolinium or -isoquinolinium iodides and commercially available ethyltrimethylsilyl acetate (ETSA). The methylene carbanion was generated by fluorodesilylation using caesium fluoride. On exposure to air, the ethoxycarbonylmethyl adducts were oxidised, leading to the corresponding alkylidene derivatives 4 and 5, whereas 2a in solution led slowly to its regioisomer 6a.

Spectres de vibration de composés organiques des éléments de la colonne IVB—XIV. Etude physico-chimique de germa-2 azolidines, digerma-2,5 azolidines et de cyclodi- et tri-germazanes☆

A physicochemical study (i.r., Raman) about a series of 2-germaazolidines, 2,5-digermaazolidines and cyclodi- and tri-germazanes is presented. Infrared and Raman spectra were examined and led to the following conclusions: vibrations ν(GeN) and νs(GeNGe) are located between 500 and 620 cm−1 and the νa(GeNGe) mode between 750 and 900 cm−1. The influence of the dimension and the substitution of each cycle upon those vibrations is discussed. Evidence of a relation between (νa - νs)GeNGe and the size of the cycle is presented for cyclodi- and trigermazanes. An extension of this study to derivatives with an MXM sequence (X = N or O), (M = Si, Ge, Sn) has shown that a linear relation can be established between the characteristic frequencies of the MOM group and the corresponding angle.

Sur l'obtention d'enoxysilanes par action d'hexaalkyldisilanes sur des cetones enolisables, en milieu HMPT

Abstract The action of hexaalkyldisilanes on enolisable ketones in an HMPT medium and in the presence of catalytic amounts of sodium, gives rise to, besides hydrogenosilanes, enoxysilanes which can be isolated under certain conditions. When different orientations of enolisation are possible, a change in the experimental conditions leads to a change in the nature of the predominant enoxysilane structures. Under the present conditions, the degradation and the possible isomerisation reactions of the enoxysilanes proved to be without great influence on the observed orientations. A mechanism of this silylation reaction is proposed; the obtained orientations are governed by kinetic or thermodynamic control according to the choice of method.

Synthesis of disilylmethanes and polysilacarbosilanes, precursors of silicon carbide-based materials

Abstract Using a new procedure, substituted disilylmethanes have been prepared from chlorosilanes, dichloromethane, and magnesium in tetrahydrofuran. Bis(chlorosilyl)methanes can be used as comonomers for the synthesis of polysilacarbosilanes, which are transformed into polycarbosilanes, precursors of silicon carbide.