Exhaustively Trichlorosilylated C₁ and C₂ Building Blocks: Beyond the Müller–Rochow Direct Process

Abstract

The Cl-induced heterolysis of the Si-Si bond in SiCl generates an [SiCl] ion as reactive intermediate. When carried out in the presence of CCl or ClC═CCl (CHCl solutions, room temperature or below), the reaction furnishes the monocarbanion [C(SiCl)] ([A]; 92%) or the vicinal dianion [(ClSi)C-C(SiCl)] ([B]; 85%) in excellent yields. Starting from [B], the tetrasilylethane (ClSi)(H)C-C(H)(SiCl) (HB) and the tetrasilylethene (ClSi)C═C(SiCl) (B; 96%) are readily available through protonation (CFSOH) or oxidation (CuCl), respectively. Equimolar mixtures of HB/[B] or B/[B] quantitatively produce 2 equiv of the monoanion [HB] or the blue radical anion [B], respectively. Treatment of B with Cl ions in the presence of CuCl furnishes the disilylethyne ClSiC≡CSiCl (C; 80%); in the presence of [HMeN]Cl, the trisilylethene (ClSi)C═C(H)SiCl (D; 72%) is obtained. Alkyne C undergoes a [4+2]-cycloaddition reaction with 2,3-dimethyl-1,3-butadiene (CHCl, 50 °C, 3d) and thus provides access to 1,2-bis(trichlorosilyl)-4,5-dimethylbenzene (E1; 80%) after oxidation with DDQ. The corresponding 1,2-bis(trichlorosilyl)-3,4,5,6-tetraphenylbenzene (E2; 83%) was prepared from C and 2,3,4,5-tetraphenyl-2,4-cyclopentadien-1-one under CO extrusion at elevated temperatures (CHCl, 180 °C, 4 d). All closed-shell products were characterized by H,C{H}, and Si NMR spectroscopy; an EPR spectrum of [ nBuN][B] was recorded. The molecular structures of [ nBuN][A], [ nBuN][B], B, E1, and E2 were further confirmed by single-crystal X-ray diffraction. On the basis of detailed experimental investigations, augmented by quantum-chemical calculations, plausible reaction mechanisms for the formation of [A], [B], C, and D are postulated.

Tris(trichlorosilyl)tetrelide Anions and a Comparative Study of Their Donor Qualities

“…Treatment of [Et 4 N][GeCl 3 ] in CH 2 Cl 2 with 3 equiv of Si 2 Cl 6 resulted again in the formation of [Et 4 N][ 3 ], which confirmed the role of [GeCl 3 ] − as the first intermediate of the reaction cascade leading to [ 3 ] − : analogous to the case of CCl 4 , chlorophilic attack of [SiCl 3 ] − on GeCl 4 removes a Cl + cation. However, while [CCl 3 ] − is nucleophilic enough to bite back into SiCl 4 and form Cl 3 C−SiCl 3 , [GeCl 3 ] − behaves inert toward SiCl 4 . Toward the more reactive Si 2 Cl 6 , [GeCl 3 ] − likely acts as a Cl − donor to afford GeCl 2 and [SiCl 3 ] − /SiCl 4 , which subsequently combine to establish a Ge−Si bond in a putative [Cl 2 GeSiCl 3 ] − anion.…”

“…The methanide [ 1 ] − is accessible in >90 % yield from CCl 4 and in situ generated [SiCl 3 ] − (Scheme ) . The silanide [ 2 ] − was first identified on the basis of 29 Si NMR spectroscopy and later structurally characterized by Beckmann, Ketkov, and Mebs, who isolated [ 2 ] − as a side product of the synthesis of SiCl 2 (IDipp) .…”

“…For a discussion of the trigonal‐planar anion [ 1 ] − , see Refs. and the Supporting Information of this paper. The Si and Ge centers in [ 2 ] − and [ 3 ] − are strongly pyramidalized [Σ(SiSiSi)=290.0°, Σ(SiGeSi)=285.5°].…”

“…In the case of [ 1⋅ GaCl 3 ] − versus [ 1 ] − , the SiCl 3 resonance undergoes a downfield shift to δ ( 29 Si)=−3.4 ppm (cf. H[ 1 ]: −2.6 ppm) . The resonances of the other two adducts experience almost identical upfield shifts to δ ( 29 Si)=11.9 ppm ([ 2⋅ GaCl 3 ] − ; cf.…”

“…Compound 5 can quantitatively be transformed into its perhydrogenated congener 5 H , a promising precursor for the deposition of Si/Ge‐based thin films. As an outlook, we emphasize that [ n Bu 4 N][ 2 ] reacts with C 2 Cl 6 to give the ethylene‐dianion salt [ n Bu 4 N] 2 [(Cl 3 Si) 2 C−C(SiCl 3 ) 2 ] . The scope of this Si−C bond‐forming reaction, which is conceptually similar to the use of [(Cl 3 Si) 2 P] − and chloroalkanes for the formation of P−C bonds, will be explored in the future.…”