C. Guerin

Hypervalent silicon hydrides: evidence for their intermediacy in the exchange reactions of di- and tri-hydrogenosilanes catalysed by hydrides(NaH,KH and LiAlH4)

Di- and tri-hydrogenosilanes, RR′SiH2 and RSiH3 (R = aryl, allyl or benzyl; R′ ue5fb aryl or alkyl), readily undergo exchange reactions, involving siliconue5f8carbon bonds and silicon-hydrogen bonds, in the presence of hydrides (LiAlH4, KH and NaH) as catalysts. These results are discussed in terms of five-coordinate silicon hydrides as intermediates in the reaction.

A general route to five-coordinate hydridosilicates

Abstract Five-coodinate potassium hydridosilicates, [HSi(OR) 4 ] − K + (R ue5fb Et, i-Pr, Ph), have been obtained in good yield from the reaction of a trialkoxy- or triarylox-silane with the corresponding potassium alkoxide or aryloxide, and characterized spectroscopically. Reaction of the hydrosilicates with an excess of Grignard reagent gives the corresponding triorganosilanes.

Pentavalent hydridosilicates: some aspects of the reactivity of potassium tetraethoxyhydridosilicate

Abstract Some reactions of the pentacoordinate tetraethoxyhydridosilicate, [HSi(OEt) 4 ] − , are reported. The ready reduction of ketones and aldehydes in the absence of a catalyst indicates the high reactivity of the Siue5f8H bond in this compound which also readily shows good one electron transfers to an appropriate substrate.

Le bis(triméthylsilyl)-1,3-propène comme précurseur des silyl-1-butadiènes; Étude de leur complexation par Fe(CO)5, Fe2(CO)9, et (MeCp)Mn(CO)3

Abstract Reactions of 1,3-bis(trimethylsilyl)propene with carbonyl compounds in the presence of fluoride ions as catalysts, produce selectively ( E )-1-trimethylsilylbut-1-en-4-ol. 1,3-Bis(trimethylsilyl)propenyllithium reacts with carbonyl compounds, under formation of 1-trimethylsilylated dienes. The reactions of these dienes with Fe(CO) 5 , Fe 2 (CO) 9 and (MeCp)Mn(CO) 3 are reported; they are good precursors for η 4 -dienyl complexes.

Hypervalent silicon hydrides: evidence of their intermediacy in the reaction of optically active 1-NpPhMeSiH(D) with hydrides

Abstract Racemisation of optically active 1-NpPhMeSi★H(D) takes place rapidly in the presence of hydrides (KH, LiAlH4, or LiAlD4) in THF at room temperature. Under more drastic conditions, i.e. 50°C for 24 h, (+)-1-NpPhMeSiH gave the racemic (±)-1-NpPhMeSi− anion. The results are discussed in terms of initial addition of H− to silicon to generate a pentavalent organosilicon anion.

Five-coordinate potassium dihydridosilicates: synthesis and some aspects of their reactivity

Abstract Five-coordinate potassium dihydridosilicates, K+[H2Si(OR)3]− (R = Et, i-Pr) have been obtained by reaction of a trialkoxysilane with potassium hydride. Reaction of the dihydridosilicate with an excess of a Grignard reagent gives the corresponding diorganosilane. The ease of reduction of carbonyl compounds by the dihydridosilicate in the absence of a catalyst is indicative of the high reactivity of the Siue5f8H bond in such species.

Le bis(trimethylsilylallyl)-1,3 propene comme precurseur du bis[η3-(trimethylsilyl-1-allyl)chloropalladium], synthese de vinylsilanes fonctionnalises (E)

Abstract Treatment of the 1,3-bis(trimethylsilyl)propene by Li2PdCl4 (1 equiv.) in methanol affords the bis[η3-(1-trimethylsilylallyl)chloropalladium] complex. Alkylation of this derivative with sodium malonates leads to (E)-vinylsilanes.

Metallation des chlorosilanes par les trialkylstannylanions

Abstract The stereochemistry of chlorosilane metallation by stannyl anions of the silacyclopentane series has been studied. Poor stereoselectivity is often observed for this reaction and the expected stannylsilanes are usually contaminated with products of side reactions. Concerning the mechanisms implied in the stannylation reaction, we consider that a reasonable interpretation of the experimental facts is the possibility of two competing processes: nucleophilic SN2 substitution (inversion at Si) and halogen-metal exchange (which implies retention or epimerization at the Si atom).

Coordination chemistry of siloles: reaction of η4-complexed endo-1-chloro-2,5-diphenylsilacyclopentadiene with lithium reagents. Synthesis of new carbenes, and the crystal structure of dicarbonylphenyl(η4-exo-1-methyl-1-oxy-2,5-diphenylsilacyclopentadiene)carbene iron

Abstract The reaction of MeLi, PhLi and i-Pr 2 NLi with (η 4 - endo -1-chloro- exo -1-methyl-2,5-diphenylsilacyclopentadiene)tricarbonyliron ( 1 ) has given a neutral carbene with an unusual cyclic structure. An X-ray structure determination was carried out in the case of the product, 4b , from PhLi.