Abstract
The reactions of the PMe3 adduct of the silylated germylene [(Me3Si)3Si]2Ge: with GeCl2·dioxane were found to yield 1,1-migratory insertion products of GeCl2 into one or two Ge–Si bonds. In a related reaction, a germylene was inserted with tris(trimethylsilyl)silyl and vinyl substituents into a Ge–Cl bond of GeCl2. This was followed by intramolecular trimethylsilyl chloride elimination to another cyclic germylene PMe3 adduct. The reaction of the GeCl2 mono-insertion product (Me3Si)3SiGe:GeCl2Si(SiMe3)3 with Me3SiC≡CH gave a mixture of alkyne mono- and diinsertion products. While the reaction of a divinylgermylene with GeCl2·dioxane only results in the exchange of the dioxane of GeCl2 against the divinylgermylene as base, the reaction of [(Me3Si)3Si]2Ge: with one GeCl2·dioxane and three phenylacetylenes gives a trivinylated germane with a chlorogermylene attached to one of the vinyl units.
Highlights
Low valent main group compounds such as carbenes and their higher congeners have attracted much attention due to their transition metal-like behavior [1,2,3,4]
Reactions of silylenes and germylenes with alkynes lead to oxidation and the formation of tetravalent sila- and germacyclopropenes [6,7,8,9,10,11,12], the observed phenylacetylene insertion case benefits from the fact that formation of the vinylgermylene PMe3 adduct (2) is thermodynamically favored compared to the respective germacyclopropene, which exists as an intermediate on the reaction pathway [13]
The reaction of 1 with one equivalent of GeCl2 ·dioxane resulted in the formation of compound 3 (Scheme 2, Figure 1), which can be considered a 1,1-migratory insertion product of GeCl2 into an Si–Ge bond of 1
Summary
Low valent main group compounds such as carbenes and their higher congeners have attracted much attention due to their transition metal-like behavior [1,2,3,4]. While most of this similarity refers to the oxidative addition and reductive elimination processes, other elementary reaction steps typical for transition metals are possible. A most unusual reaction of this compound, we observed the regioselective 1,2-migratory insertion of phenylacetylene into one or two of the Ge–Si bonds of 1 (Scheme 1) [5]. Reactions of silylenes and germylenes with alkynes lead to oxidation and the formation of tetravalent sila- and germacyclopropenes [6,7,8,9,10,11,12], the observed phenylacetylene insertion case benefits from the fact that formation of the vinylgermylene PMe3 adduct (2) is thermodynamically favored compared to the respective germacyclopropene, which exists as an intermediate on the reaction pathway [13].
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