Stereodivergent sila-germylenation vs. sila-stannylenation of an internal alkyne.

We report on the insertion of electron deficient alkyne, dimethyl acetylene dicarboxylate (DMAD), into the E–Si bond of hypersilyl tetrylenes, PhC(NtBu)2ESi(SiMe3)3 (E = Ge and Sn), at room temperature. Uniquely, the germylene leads to cis alkenes, while the stannylene gives access to trans alkenes, and the insight into divergent stereoselectivity has been obtained by DFT studies. [ABSTRACT FROM AUTHOR]