Silane, trimethyl trichloro

The method has been further improved." Trimethyl(perfluoroalkyl)silanes RpTMS (Rp = c, -C, perfluoroaliphatic groups) are prepared by reaction of perfluoroalkyl halides RpX (X = Br, I) with chlorotrimethylsilane in the presence of tris(dialkylamino)phosphanes in acetonitrile. For example, chlorotrimethylsilane was treated with bromotrifluoromethane and tris(diethylamino)phosphane in acetonitrile at — 40"C for 1 hour to give trimethyl(trifluo-romethyl)silane in 90% yield. Bis(dimethylamino)(trifluoromethyl)silane is available from the reaction of chlorobis(dimethylamino)silane with the system bromotrifluoromethane/tris-(diethylamino)phosphane, while trichloro(trifluoromethyl)silane is prepared by nucleophilic trifluoromethylation of tetrachlorosilane with bromotrifluorornethane/tris(diethylamino)phos-phane. " ... 

The reaction of trimethyl(perfluorophenyl)stannane with germanium(l V) chloride also proceeds smoothly, but the yield of trichloro(perfluorophenyl)germane (II. X = Cl) is rather low. Germanium(lV) bromide completely reacts with trimethyl(perfluorophcnyl)stannane over 22 hours. Apart from bromotrimethyltin. the reaction produces dibromodimethyltin. which makes it diflficult to isolate the target product. The reaction of germanium(IV) chloride with trimethyl(perlluorophenyl)silane does not proceed at a high temperature (240 C, 46 h), or in acetonitrile in the presence of cesium fluoride (50 C. 7 h). 

The thermal decomposition of trichloro- or trifluoro(trichloromethyl)silane or the fluoride ion induced decomposition of trimethyl(trichloromethyl)silane, in the presence of an alkene (Houben-Weyl, Vol. 4/3, p 155 and Vol. El9b, p 1535). 

Use of the more reactive tetrabromosilane leads to the bis- and tris-(chloro-methyl) compounds without the necessity for a catalyst.383 Diazomethane reacts with trichlorosilane or trichloro(methyl)silane in the presence of copper powder to yield, respectively, dichloro(chloromethyl)silane385 386 and di-chloro(chloromethyl)(methyl)silane,383 but no chloromethyl derivative can be obtained in this way from chlorosilanes carrying three organic groups, such as chloro-(trimethyl), -(triethyl)-, and -(triphenyl)-silane. 

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