Beryllium-Based Anion Sponges: Close Relatives of Proton Sponges.

Through the use of high-level ab initio and density functional calculations it is shown that 1,8-diBeX-naphthalene (X=H, F, Cl, CN, CF3 , C(CF3 )3 ) derivatives behave as anion sponges, very much as 1,8-bis(dimethylamino)naphthalene derivatives behave as proton sponges. The electron-deficient nature of the BeX substituents, which favors strong charge transfer from the anion towards the former, results in anion affinities that are among the largest ones reported for single neutral molecules.