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

Abstract

Treatment of hexakis(2,4,6-triisopropylphenyl)tetragermabuta-1,3-diene (2) with selenium in the presence of Et 3 P 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 Et 3 PTe 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 R 4 Ge 4 Te 6 , R = 2,4,6-iPr 3 C 6 H 2 , 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) A, respectively.