Reaction Modes of a Tetragermabutadiene: Cycloadditions versus Ge−Ge Bond Cleavages¹

Treatment of hexakis(2,4,6-triisopropylphenyl)tetragermabuta-1,3-diene (2) with selenium in the presence of Et3P furnishes a selenatetragermacyclopentene derivative with an endocyclic Ge−Ge double bond. With small amounts of water 2 reacts to afford an oxatetragermacyclopentane, analogous to THF. The reaction of 2 with Et3PTe proceeds by cleavage of all Ge−Ge bonds to yield a 1,2,4,5-tetratellura-3,6-digermacyclohexane derivative together with small amounts of the “double-decker” compound R4Ge4Te6, R = 2,4,6-iPr3C6H2, and a telluradigermirane. In the reaction of 2 with 2-methoxyphenyl isocyanide one Ge−Ge double bond is cleaved to give the 4(1H)-trigermatimine ring system with an endocyclic Ge−Ge double bond and the known tetrakis(2,4,6-triisopropylphenyl)digermene (10). All new compounds were characterized by X-ray crystallography. Redetermination of the structure of 10 revealed two independent molecules with GeGe bond lengths of 2.2894(6) and 2.2635(14) Å, respectively.