Preparation, structural characterization of 1,2-digermacyclobut-3-enes, and their palladium-catalyzed insertion of alkynes

1,2-Digermacyclobut-3-enes were prepared by the treatment of Z-α,β-bis(chlorodialkylgermyl)ethenes with Na metal in boiling toluene and their structures were fully established by spectroscopic methods coupled with X-ray crystallography. In the presence of an appropriate catalyst, 1,2-digermacyclobut-3-enes reacted smoothly with alkynes to give the corresponding insertion products, 1,4-digermacyclohexa-2,5-dienes in moderate to good yields. Conventional complexes, such as [Pd(PPh3)4] and [Pt(PPh3)4], serve as efficient catalysts. The mechanism of the insertion reaction of alkynes into the germanium–germanium bond of 1,2-digermacyclobut-3-enes is discussed in terms of a key intermediate, a 1,4-digerma-2-buten-1,4-diylpalladium.

Graphical abstract1,2-Digermacyclobut-3-enes, prepared by the treatment of Z-α,β-bis(chlorodialkylgermyl)ethenes with Na metal, reacted with alkynes to give the corresponding insertion products in the presence of palladium and platinum complexes. The mechanism of the insertion reaction is discussed in terms of 1,4-digerma-2-buten-1,4-diylpalladium as a key intermediate.Figure optionsDownload full-size imageDownload as PowerPoint slide