Frustrated Lewis pair adducts of alkynyl-capped tetrelenes.

The frustrated Lewis pair (FLP) adducts PB{ECl 2 } (PB = i Pr 2 P(C 6 H 4 )BCy 2 ; Cy = cyclohexyl; E = Si, Ge) were used to access a bis(alkynyl)-functionalized silylene and a germylene; the goal behind preparing these species was to obtain new unsaturated main group polymers [E(CCSiMe 3 ) 2 ] n upon heating. While the silylene adduct PB{Si(CCSiMe 3 ) 2 } was stable up to 150 °C, the heavier element congener PB{Ge(CCSiMe 3 ) 2 } underwent a complicated rearrangement process accompanied by Cy-group migration and Ge(II)-alkyne coordination. Density functional theory computations were performed to understand the mechanistic pathway for the unusual rearrangement of PB{Ge(CCSiMe 3 ) 2 }.