Hypersilyl compounds

Methoxy-bis[tris(trimethylsilyl)silyl] methane The First Geminal Di(hypersilyl) Compound... 

Keywords Hypersilyl compounds / Tris(trimethylsilyl)silyl derivatives / Polysilanes... 

R188 W. Krumlacher, H. Siegl and K. Hassler, Hypersilyl Compounds of Elements of Group 15 , p. 367... 

Geminal Di(hypersilyl) Compounds Synthesis, Structure and Reactivity of some Stericaliy Extremely Congested Molecules... 

Keywords Hypersilyl Compounds / Tris(trimethylsilyl)silyl Derivates / X-Ray... 

Summary The synthesis of derivatives of the type [(Me3Si)3Si]2CHR (R = OH, OCH3, 0C(0)H, 0C(0)Me, NMe ) proved to be surprisingly facile and was achieved by the reaction of tris(trimethylsilyl)silyllithium (1) with suitable Ci building blocks. The results of the X-ray analyses and reactions of these di(hypersilyl) compounds are described in this paper. 

The molecular structures of 3, 4 and 6 are demonstrated in the Figs. 1-3, respectively, and Table 1 shows the most important structural data. Two bulky substituents at one comparatively small carbon atom lead to tremendous sterie distortions in all di(hypersilyl) compounds. 

Solvent-free hypersilanides have been shown to be useful reagents for the preparation of other especially low coordinated hypersilyl derivatives. The thallium(II) compound 6 [1] or derivatives of divalent tin 7 [3] and lead 8 [3] were synthesized via the reactions of (Me3Si)3SiRb (4) with the bis(trimethylsilyl)amides of thallium(I), tin(II), and lead(II), respectively. 

Here we report the syntheses of solvent-free hypersilyl derivatives of sodium and lithium -(Me3Si)3SiLi (1) and (Me3Si)3SiNa (2) - for the first time. Moreover, we are presenting the crystal structures of unsolvated lithium 1, sodium 2, and potassium 3 derivatives and of two additional solvent adducts of the cesium compound 5. 

In hypersilyl sodium and potassium both, infra- and intermolecular M "H-C agostic interactions occur, leading to short M -C distances. Interactions of this type were found in many other alkali metal compounds - a survey is given in reference [5]. In the hypersilyl lithiiun dimers only short znframolecular M--H-C contacts are observed (M "C 239, 245 pm), combined with a significant lengthening of the involved Si-C bonds (191 pm) and a pronounced tilting of the hypersilyl ligands (Fig. 3). 

The hypersilyl group allows isolation of stable gallium silyl compounds with tri- and tetracoordinated gallium centres. The GaSi bond seems to be inert to protic reagents. 

In reactions of potassium hypersilyltellurolate with chlorosilanes as shown in Scheme 1 sometimes hypersilyl chloride and organosilicon tellurides have been observed as by-products, e. g., the preparation of 1 yielded the six membered ring compound (Ph2SiTe)3 (2) as a minw by-product. 2 can also be prepared from Ph2SiCl2 by treatment with Li2Te (from LiBEtsH and Te) ... 

The preparation of compounds 2-4 is summarized in Scheme 1. The required starting material, donor solvent-free hypersilyl potassium (1) [26], was prepared by thermally induced desolvation of KHyp(thf)x which itself is easily accessible from tetrakis(trimethylsilyl)silane and potassium tert-butoxide [27]. 

Rearrangement of Bis(hypersilyl)silylene and Related Compounds An Unusual Way to Three-Membered Rings... 

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