In 1872, van't Hoff¹ and LeBel² proposed that tetracoodinate carbon compounds must have a tetrahedral rather than a planar arrangement. Almost a century after the publication of van't Hoff-LeBel model, Hoffmann, Alder and Wilcox³ suggested rules to stabilize molecules containing planar tetracoordinate carbon atoms (ptC). Since 1970, several molecules with a ptC have been proposed in silico and characterized experimentally.

            The simplest molecule with a ptC surrounded by four carbon atoms is C₅^2-.⁴ This cluster and its metallic salts were the first examples of molecules containing a ptC with a C(C)₄ skeleton stabilized exclusively by electronic factors. We now present a series of cyclic saturated hydrocarbons containing a ptC (Figure 1). The stability and bonding scheme are analyzed through the study of the molecular orbitals and activation barriers involved into transition of ptC species to more stable isomers.

(1)                 van't Hoff., J. H. Arch. Neerl. Sci. Exactes Nat. 1874, 445.

(2)                 LeBel, J. A. Bull. Soc. Chim. Fr. 1874, 22.

(3)                 Hoffmann, R.; Alder, R.; Wilcox Jr, C. F. J. Am. Chem. Soc. 1970, 92, 4992.

(4)                 Merino, G; Mendez-Rojas, M. A.; Vela, A. J. Am. Chem. Soc. 2003, 125, 6026.

Merino, G.; Mendez-Rojas, M. A.; Vela, A.; Heine, T. J. Comp. Chem. 2007, 1, 362-372.  Keese, R. Chem. Rev. 2006, 106, 4787.

Perez, N.; Heine, T.; Barthel, R.; Seifert, G.; Vela, A.; Méndez-Rojas, M. A.; Merino, G. Org. Lett. 2005, 7, 1509.