A Chemical Trick:  How To Make a Digermene from a Disilene, Formation of ³Δ-1,2,3,4-Disiladigermetene

Abstract

The unexpected reaction of tetrakis[di-tert-butyl(methyl)silyl]disilagermirenes (1a and 1b) with GeCl2.dioxane results in the quantitative formation of trans-1,2-dichloro-1,2,3,4-tetrakis[di-tert-butyl(methyl)silyl]-3Delta-1,2,3,4-disiladigermetene, 2, representing the first cyclotetrametallene containing two different heavier group 14 elements and the first digermene incorporated in a four-membered ring. trans-1,2-Dichloro-1,2,3,4-tetrakis[di-tert-butyl(methyl)silyl]-3Delta-1,2,3,4-disilagermastannetene (8), with a Ge=Sn double bond, was also prepared by the reaction of 1 with SnCl2.dioxane. The crystal structure of 2 was established by X-ray crystallography, which showed a folded four-membered ring skeleton with a long Ge=Ge double bond (2.2911(4) A). The structural peculiarities of 2, as well as the possible mechanism of its formation, are also discussed.

Formation and Properties of a Bicyclic Silylated Digermene

“…[ 22 ] The Ge–Ge double bond of 2.2663(9) Å is slightly shorter than other tetrasilylated digermenes reported so far. [ 30 , 34 ] Also the Si–Ge bonds of 2.371(2) and 2.366(1) Å are unusually short and in the same range as the Si–Si bonds in the molecule. While 2 has a very small trans –bent angle of 2.5° the twisting angle between the disilylated germylene units, τ , is 16.2°.…”

Aromaticity of Group 14 Organometallics: Experimental Aspects

“…One of the best methods for making EE′ double bonds is the dehalogenative reduction of the 1,2‐dihalogen precursors of the type E(X)E′(X) (X=halogen) with alkali metals. For this reason, for the preparation of the heavy analogues of cyclobutadiene dianions, initially we designed the appropriate precursors: trans ‐1,2‐dichloro‐ 3 Δ‐1,2,3,4‐disiladigermetene 21 81 and trans , trans , trans ‐1,2,3,4‐tetrabromo‐1,2,3,4‐tetrasiletane 22 72b. The formation of the target 1,2‐disila‐3,4‐digerma‐ and 1,2,3,4‐tetrasilacyclobutadiene dianions [ 23 2− {K + (thf) 2 } 2 ] and [ 24 2− {K + (thf) 2 } 2 ] was smoothly achieved by the reduction of 21 or 22 with potassium graphite KC 8 (4.2 and 6.9 equiv, respectively) in THF (Scheme ) 82.…”

The First Bicyclo[1.1.0]butane Dianion of Heavier Group 14 Elements

“…However, the stable, charged derivatives (both anionic and cationic) of bicyclo[1.1.0]butanes have remained elusive species until now: neither bridgehead 1,3‐ (Scheme 1, C ) nor bridging 2,4‐dianions (Scheme 1, D ) of bicyclo[1.1.0]butane have ever been isolated and characterized 5. Very recently we have synthesized the 3 Δ‐1,2,3,4‐disiladigermetene 1 ,6 which appeared to be a most promising candidate for reduction to produce the corresponding dianion species. Indeed, by the reaction of 1 with alkali metals, the heavy analogues of the cyclobutadiene dianion were synthesized; their cyclic 6 π‐electron system was demonstrated to be non‐aromatic 7.…”