The reactions of bridged tris(trimethylsilyl)silyl fragments with 2 molar equiv of potassium tert-butoxide allow the generation of R,ω-oligosilyl dianions (1a, 2a, 3a, 4a). Depending on the nature of the spacer between the oligosilyl units, these compounds can be used to generate either linear or cyclic derivatives. They are especially attractive for the formation of homoand heterocyclosilanes, as exemplified by the synthesis of sila-, stanna-, and zirconocenacyclosilanes. A linear bis(potassiumsilyl)acetylene (4a) was used to bridge two zirconocene units, (Cp 2 Zr(Cl)Si(SiMe 3 ) 2 CCSi(SiMe 3 ) 2 Zr(Cl)Cp 2 ) (11).

The synthesis of several bis(polysilanyl)magnesium, polysilanylmagnesium bromide compounds was accomplished by metathesis of the respective potassium polysilanyls with magnesium bromide. The compounds were isolated as adducts of THF, TMEDA, or 1,4-dioxane. The use of Grignard reagents PhMgBr and MeMgBr instead of magnesium bromide led to the formation of mixed alkyl/polysilanylmagnesium compounds.

Syntheses of NHC adducts of bis[tris(trimethylsilyl)silyl]germylene and -stannylene and some structurally related cyclic disilylated stannylenes are reported. Reactions of a cyclic stannylene NHC adduct with gold and silver cyanide led to cationic metal complexes with two cyanostannyl ligands. The Ag complex decomposed 1304 further to a cyanostannide. Reactions of bis[tris(trimethylsilyl)silyl]germylene and -stannylene NHC adducts with gold and silver cyanide displayed more unusual coordination chemistry with one silyl group of the ylene unit being transferred to the group 11 metal.One particularly interesting class of compounds in this chemistry is that of heavier divalent group 14 compounds (tetrylenes). [12,13] Our own recent studies focus on silylated tetrylenes, [14][15][16][17][18][19][20][21][22][23][24][25] first examples of which were reported by Klinkhammer and Schwarz, who prepared bis[tris(trimethylsilyl)silyl]stannylene and -plumbylene. [26] While Klinkhammer found that bis[tris(trimethylsilyl)silyl]stannylene is monomeric in solution our own attempts to prepare a cyclic variation of this compound showed that dimerization occurred. [14] In order to prevent the dimerization process we carried out the preparation in the presence of triethylphosphane, which led to the formation of a stannylene base adduct. [14] Klinkhammer reported that bis[tris(trimethylsilyl)silyl]stannylene also undergoes adduct formation with phosphanes [27] and later Castel, Escudié, and co-workers demonstrated that even NHC adducts of the compound can be obtained. [28] Results and DiscussionAs mentioned, Klinkhammer already reported phosphane adduct formation of bis[tris(trimethylsilyl)silyl]stannylene. [27,29] Recently we have described synthesis and characterization of a triethylphosphane adduct [17] and also the respective trimethylphosphane adduct 2 is easily accessible from the reaction of 2 equiv. of tris(trimethylsilyl)silylpotassium (1) with SnCl 2 in the presence of PMe 3 (Scheme 1). Scheme 1. Synthesis of bis[tris(trimethylsilyl)silyl]stannylene and germylene base adducts. Journal of Inorganic and General ChemistryZeitschrift für anorganische und allgemeine Chemie www.zaac.wiley-vch.de ARTICLE Analogous reactions of 1 with SnCl 2 or GeBr 2 in the presence of 1,3,4,5-tetramethylimidazol-2-ylidene ( Me IMe) gave the respective NHC adducts 3 [25] and 4 (Scheme 1). Syntheses of the analogous 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene ( Me IPr) stannylene [28] and germylene [21] adducts were reported before. Single crystal diffraction analysis of 2 ( Figure 1) and 4 ( Figure 2) provided structural proof.

Reactions of potassium oligosilanyls with ZnCl(2) lead to the formation of oligosilanylzinc compounds with zinc's coordination sphere expanded by ligation of TMEDA, an additional oligosilanyl group, or a chloride ion.

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