Silanes, perfluoroalkyl

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 reactions of trimethyl(perfluoroalkyl)silanes RpTMS [Rp = CFj, CF2CF3, (CF2)2CFj] with a variety of fluorinatcd organic and inorganic substrates containing a S —O or C —O double bond have received attention. Perfluoroalkyl- and perfluoroarylsilancs can also be effectively used to directly replace active fluorine atoms bound to carbon by a variety of fluorinatcd moieties. 

Alkyl halides, including bcnzylic and allylic halides, do not react with trimethyl(trifluoro-methyl)silane. even with molar amounts of tetrabutylammonium fluoride. A convenient method has been developed for the perfluoroalkylation of organic (aryl, vinyl, benzyl and allyl) halides, e.g. formation of 1. using a mixture of trialky (perfluoroalkyl)silane/potas-sium fluoride/copper in dimethylformamide. Under these conditions perfluoroalkylcopper RpCu reagents are produced in situ. 

When activated by anionic catalysts [potassium fluoride, cesium fluoride, tctraalkylammonium fluorides, tris(dimethylamino)sulfonium difluorotrimethylsilicate, phosphazenium, hexa-methylpiperidinium and cobaltoccnium fluorides, tetrabuiylammonium difluoro(triphenyl-silyl)silicatc. the complex tetrakis(dimethylamino)ethene/pcrfluoropropene, ammonium (and phosphonium) periluorocyclobuianc ylides], trimethyl(perfluoroalkyl)silanes will generate C-Rp bonds from carbon-halogen bonds. 

Trimethyl(perfluoroalkyl)silanes react with perfluorinated ketones in the presence of cesium or potassium fluoride in diethyl ether (THF, MeCN), giving perfluorinated tertiary alcohols 13. ... 

In the presence of potassium fluoride, trimethyI(perfluoroalkyl)silanes react with ketones in the diethyl ether of triethylene glycol to form the trimethylsilyl ethers of perfluoroalkylated alcohols, e.g. 17. ... 

Aromatic aldehydes give the corresponding alcohols on reaction with trimethyl(polylluoroal-kyl)silanes in lelrahydrofuran in the presence of tetramcthylammoniuni fluoridc. The reaction of perfluoro-2-propoxypropanoyl fluoride with trimethyl(perfluoroalkyl)silane leads to the perfluoroalkylated ketone product. ... 

Activated esters, such as oxalates, are also reactive towards trimethyl(perfluoroalkyl)silanes under fluoride catalysis as reported in the case of di-/cr/-butyl oxalate which affords tri-fluoropyruvic acid 26 (Rp = CFj) in hydrated fonn. ""... 

A general ketone synthesis has been developed involving reaction of trimethyl(perfluorooc-tyl)silane with acid fluorides. Yields, e.g. of 23 and 24, are generally good, and conversion of these ketones into tertiary alcohol derivatives tends to be slow, in part due to rather low solubility of the long-chain ketones.47 Indeed, it is somewhat surprising that these ketones do not react readily with trialkyl(perfluoroalkyl)silanes under these conditions to give tertiary alcohol derivatives.47... 

A similar method of activation of the perfluoroalkyl silane is used for nucleophilic addition or substitution of trifluoromethyl moieties to obtain electron-deficient fluorinated aromatic compounds [91] (Scheme 2.137). 

Scheme A.14 Copper-mediated perfluoroalkylation of iodoarenes by perfluoroalkyl silane reagents [20].

Water was chosen as a polar, and di-iodomethane as a non-polar liquid to compare the surface properties of the hybrid polymer layers containing different commercially available long chain perfluoroalkyl silanes (1 mol% each) with those of other surfaces. The measured contact angles and the surface energy data of the solids calculated according to the Owens and Wendt equation [24] are given in Table 6.3. The increase in the contact angles as a measure for a clearly reduced wettability can be observed with both test substances. 

XPS depth profile of the ohemical elements silicon, aluminium and fluorine of hybrid sol-gel layers oontaining different quantities of the long chain perfluoroalkyl silane C8Fi7C2H4Si(OR)3 (a) 5 mol-% (b) 1 mol-%... 

Table 6.3 Contact angle measurements (static values) on top of different surfaces as well as on clear and tinted hybrid sol-gel layers containing commercial long chain perfluoroalkyl silanes surface energy values were calculated in accordance with Owens and Wendt [24]...

The anti-adhesive effect becomes obvious when trying to write on a nanocomposite layer modified by a long chain perfluoroalkyl silane with a commereially available non-permanent overhead marker (Fig. 6.12). The surface reduces the wettability... 

Wettability of partially coated stainless steel substrates by a (non-permanent) overhead marker (left transparent layer right coloured layer both layers are equipped with a long chain perfluoroalkyl silane ... 

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