Oxidative Additions of C−F Bonds to the Silanide Anion [Si(C₂F₅)₃]⁻

Abstract

Compounds exhibiting main group elements in low oxidation states were found to mimic the reactivity of transition metal complexes. Like the latter, such main group species show a proclivity of changing their oxidation state as well as their coordination number by + 2, therefore fulfilling the requirements for oxidative additions. Prominent examples of such main group compounds that undergo oxidative additions with organohalides RÀ X (R = alkyl, aryl, X = F, Cl, Br, I) are carbenes and their higher congeners. Aluminyl anions, which like carbenes and silylenes oxidatively add to strong σ-bonds in RÀ X species, have been recently discovered. We present the first anion based upon a Group 14 element, namely the tris(pentafluoroethyl)silanide anion, [Si(C 2 F 5 ) 3 ] À , which is capable of oxidative additions towards CÀ F bonds. This enables the isolation of non-chelated tetraorganofluorosilicate salts, which to the best of our knowledge had only been observed as reactive intermediates before.

Polar X−H Bond (X=O, S, N) Activation at a Cage Silanide

“…It is also distinct from the concerted oxidative addition of CÀ F bonds to perfluorinated silanides computed by Hoge et al Instead, it resembles more that reported for singlet carbenes, which react with alcohols by initial protonation followed by nucleophilic capture of the resulting carbenium ion. [33,38] The thiolate adduct [K(18-crown-6)] [(tmim)SiH-(SC 6 H 4 CH 3 )] (compound 3) showed peculiar reactivity both in THF and DCM (Scheme 3). In THF, a solvent molecule inserts into the SiÀ S bond to form compound 5 by ring opening.…”

“…[30,31] Two recent studies by the group of Hoge showed that silanides bearing strongly electron withdrawing perfluoroalkyl groups display reactivity consistent with a Lewis-amphoteric character. [33,34] In particular, they undergo oxidative addition of CÀ F bonds (Figure 1c) and addition to C=O bonds to form silaepoxides.…”

Trichlorosilyl Anions of p‐Block Elements – New Applications for Simple Molecules

“…It was shown that Li[Si(C 2 F 5 ) 3 ] is a powerful nucleophilic transfer reagent which is able to transfer the tris(pentafluoroethyl)silyl group on various substrates [59] . The same group showed recently that the tris(pentafluoroethyl)silanide anion, [Si(C 2 F 5 ) 3 ] − , is capable to perform oxidative additions towards C−F bonds [60] …”

“…[59] The same group showed recently that the tris(pentafluoroethyl)silanide anion, [Si(C 2 F 5 ) 3 ] À , is capable to perform oxidative additions towards CÀ F bonds. [60] (8) Tris(trichlorosilyl)silane, H[Si(SiCl 3 ) 3 ], the educt in equation 8, has been prepared in 1977 by reaction of tetrakis(trichlorosilyl)silane with hydrogen chloride. [61,62] The chlorination of tris(trimethoxysilyl)silane with boron(III)-chloride is an alternative preparation of tris(trichlorosilyl)silane.…”

Synthesis and Properties of the Perfluoroethyl Martin Silicate: Reactivity in Solution and Solid‐State Mechanochemistry

“…The p-block elements-based derivatives bearing a strongly electron-withdrawing-C 2 F 5 moiety have recently emerged as promising tools for organic synthesis, with novel reactivities from an experimental and theoretical point of view. [1] Due to the strong Lewis acidity induced by the C 2 F 5 substituent on the central atom, access to the corresponding stable hypercoordinate phosphorus [2][3][4] or silicon [5][6][7][8][9][10] species has been reported. These species have been synthesized by addition of pentafluoroethyllithium [Li][C 2 F 5 ], obtained by metalation of the fluorinated gas HFC-125 (HC 2 F 5 ), onto the chlorinated P or Si substrate (Figure 1.a).…”