A series of mols., based on the smallest carbon cluster with one planar tetracoordinate carbon atom, C52-, are presented. To gain a better understanding about which electronic factors contribute to their stabilization, several global reactivity indexes, mol. scalar fields, and magnetic responses were calcd. The optimized bond lengths and the topol. anal. of the electron d. show that the central carbon atom in the parent dianion C52- has a planar local environment, and it is coordinated to four other carbon atoms. The bonding of the parent dianion with the metal cations is highly ionic. The magnetic properties show that the C52- derivs. are strongly diatropic and have a remarkable transferability of structural and electronic features from the anion to the salts. The theor. anal. suggests that the lithium salt, C5Li2, is the most plausible candidate for exptl. detection. [on SciFinder (R)]