Frustrated Lewis pair adducts of alkynyl-capped tetrelenes

The frustrated Lewis pair (FLP) adducts PB{ECl2} (PB = iPr2P(C6H4)BCy2; 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 00000000000000000 00000000000000000 00000000000000000 01111111111111110 00000000000000000 01111111111111110 00000000000000000 01111111111111110 00000000000000000 00000000000000000 00000000000000000 CSiMe3)2]n upon heating. While the silylene adduct PB{Si(CCSiMe3)2} was stable up to 150 degrees C, the heavier element congener PB{Ge(CCSiMe3)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(CCSiMe3)2}. Bis(alkynyl)-functionalized tetrelene (Si or Ge) adducts were accessed via frustrated Lewis pair (FLP) chelation. The lower stability and unusual rearrangement of the Ge analogue was studied by DFT computations.