No abstract

Reaction of 1,4-dipotassio-1,1,4,4-tetrakis(trimethylsilyl)tetramethyltetrasilane with [(Me3Si)2N]2Sn led to the formation of an endocyclic distannene via the dimerization of a transient stannylene. In the presence of strong donor molecules such as PEt3, the stannylene could be trapped as adduct. Reaction of the PEt3 derivative with B(C6F5)3 gave rise to the formation of the stannylene B(C6F5)3 adduct.

An organosilicon cage compound containing the sila-adamantane structural unit, which is the building block of crystalline silicon, was synthesized by the Lewis acid-catalyzed rearrangement reaction of a structural isomer.

The preparation of triethylphosphine adducts of cyclic disilylated or digermylated germylenes was achieved by reaction of 1,4-dipotassio-1,1,4,4-tetrakis(trimethylsilyl)tetramethyltetrasilane with GeBr2·(dioxane) and PEt3. Phosphine abstraction with B(C6F5)3 allowed formation of the base-free germylenes, which undergo 1,2-trimethylsilyl shifts to the germylene atom to form the respective silagermene or digermene, which further dimerize in [2 + 2] cycloadditions to tricyclic compounds. The reasons responsible for the germylenes’ completely different reactivities in comparison to the previously studied analogous stannylenes and plumbylenes were elucidated in a theoretical study.

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.

A disilylated germylene phosphine adduct was obtained by reaction of tris(trimethylsilyl)silyl potassium with PMe3 and GeCl2·dioxane. The adduct reacted with tolane to give a germacyclopropene, while reactions with phenylacetylene occurred by insertion into the Si-Ge bonds giving vinylgermylene adducts. Release of the mono- or divinylgermylenes by base abstraction led to insertion into Si-Si bonds and formation of silagermetes.

By reaction of 1,4-dipotassio-1,1,4,4-tetrakis(trimethylsilyl)tetramethyltetrasilane with PbBr2 in the presence of triethylphosphine a base adduct of a cyclic disilylated plumbylene could be obtained. Phosphine abstraction with B(C6F5)3 led to formation of a base-free plumbylene dimer, which features an unexpected single donor–acceptor PbPb bond. The results of density functional computations at the M06-2X and B3LYP level of theory indicate that the dominating interactions which hold the plumbylene subunits together and which define its actual molecular structure are attracting van der Waals forces between the two large and polarizable plumbylene subunits.