Be- and Mg-Based Electron and Anion Sponges.

By using G4(MP2) high-level ab initio methods, we show that Be and Mg derivatives of cyclopropane exhibit very large electron and anion affinities, reflecting the electron-deficient nature of the -BeX and -MgX (X=CH3 , F, Cl, CN) substituents. In particular, these compounds present electron affinities among the largest reported for neutral closed-shell systems. Their anion affinities are also among the largest reported for single neutral molecules, indeed higher than the 1,8-diBeX-naphthalene (X=F, Cl, CN) derivatives, recently shown to behave as anion sponges. Quite unexpectedly, our results indicate that the intrinsic anion affinity of the Mg-containing compounds is higher than that of the Be-containing analogs.