Derivatives of Spiropentadiene Dication: New Species with Planar Tetracoordinate Carbon (ptC) atom

In this work, nine tetrasubstituted derivatives [NH(2), OCH(3), Li, Na, Si(CH(3))(3)/SiH(2)CH(3,) P(CH(3))(2), Cl, F, and CN] of the spiropentadiene dication were analyzed within the framework of QTAIM. In the studied series, the electron-withdrawing substituents destabilize the ptC-containing spiropentadiene dication. On the other hand, stabilization of this dication is possible for electron-donating substituents only through sigma bonds, such as Li and Na. In all studied systems, according to QTAIM, the pi-electron system does not participate in the stabilization of the ptC atom in the spiropentadiene dication. sigma-electron-donating groups stabilize the spiropentadiene dication system by increasing the charge density of C(ext)-ptC bonds, whereas electron-withdrawing groups remove the charge density from C(ext)-ptC bonds.