Disilagermirene and silagermasilirene: from a stable disilene to a stable germasilene

The reaction of 2,2,2-tribromo-1-methyl-1,1-di(tert-butyl)disilane and bis[ di-tert-butyl(methyl)silyl](dichloro)germane with sodium in toluene at room temperature has produced tetrakis[di-tert-butyl(methyl)-silylidisilagermir ene. X-ray crystallography of this compound showed a trans-bent configurati on of Si=Si double bond with a bond length of 2.146 Angstrom. Disilagermire ne easily undergoes photochemical and thermal isomerization to a silagermas ilirene - first example of a stable germasilene. Reactivity of disilagermir ene and silagermasilirene as well as ab initio calculations of geometries a nd stabilities of both compounds have been studied.