COMPOUNDS OF GERMANIUM AND TIN .21. A TETRAARYLDIGERMENE WITH A SHORTGERMANIUM-GERMANIUM DOUBLE-BOND AND A NEARLY PLANAR ENVIRONMENT OF BOTH GERMANIUM ATOMS

Treatment of GeCl2 . dioxane with the Grignard reagent RMgBr (R = 2-tB u-4,5,6-Me3C6H) furnishes the tetraaryldigermene R2Ge=GeR2 (8). X-ray structure-analysis of 8 reveals a short Ge=Ge double bond, a nearly pl anar environment of both germanium atoms and extremely widened C-Ge-C angles of 128 degrees. In solution, 8 dissociates into two germylene m olecules R2Ge: which can be trapped with oxygen or by [4 + 1] cycloadd ition reactions with 1,4-dihetero-1,3-dienes. A similar cycloadduct of a stannylene was obtained by thermolysis of (R'Sn-2)(3) (R' = 2,4,6-i Pr(3)C(6)H(2)), in the presence of a 1,4-diazabutadiene and characteri zed by an X-ray structure-analysis.