Formation of an NHC-stabilized heterocyclic housane and its isomerization into a cyclopentenyl anion analogue.

Addition of :P[triple bond, length as m-dash]C-tBu to the NHC-coordinated trisilacyclopropylidene Si3Mes4NHCiPr2Me2 afforded a heavier analogue of a bicyclo[2.1.0]pentane, a so-called "housane", that rearranges under irradiation with a high-pressure mercury lamp or at 60 °C to an NHC-stabilized cyclopentenyl anion isomer with a three-center four-electron (3c-4e) π-bond.