Stabilization of square planar silicon: a new building block for conjugated Si-containing systems.

The feasibility of square planar silicon as a building block for conjugated systems was investigated by ab initio calculations. A five-membered ring model system was used to map electronic and steric substituent effects that might help in the stabilization of the planar structure. A pi push-pull arrangement around the silicon was found to prefer planarity. Aromaticity was proven to play an important role in stabilization as well. With the help of steric constraints, a new structure was proposed as a synthetic target containing square planar silicon. The kinetic stability of this structure was also investigated.