“…The high binding energy of an extra electron in a MX kþ1 À anion is due to delocalization of the extra electron over the large number of ligand atoms. Superhalogens with polyvalent ligands are described by the formula [10] MX k/mþ1 where k is the maximal formal valence of M and m is the normal valence of X that factors m, for example, ClO 4 or PO 3 . No exception to the superhalogen formula was found in studies of halogen-containing superhalogens MX 2 (M ¼ Li, Na; X ¼ Cl, Br, I), [11][12][13] MX 3 (M ¼ Be, Mg, Ca; X ¼ Cl, Br), [14][15][16] OF 3 , [17] MX 4 (M ¼ B, Al; X ¼ F, Cl, Br), [18][19][20] SiF 5 , [21] SiCl 5 , [22] GeF 5 , [23] PF 6 , [24] and PCl 6 .…”