Are beryllium-containing biphenyl derivatives efficient anion sponges?

The structures and stabilities of 2,2'-diBeX-1,1'-biphenyl (X = H, F, Cl, CN) derivatives and their affinities for F^-, Cl^-, and CN^- were theoretically investigated using a B3LYP/6-311 + G(3df,2p)//B3LYP/6-31 + G(d,p) model. The results obtained show that the 2,2'-diBeX-1,1'-biphenyl derivatives (X = H, F, Cl, CN) exhibit very high F^-, Cl^-, and CN^- affinities, albeit lower than those reported before for their 1,8-diBeX-naphthalene analogs, in spite of the fact that the biphenyl derivatives are more flexible than their naphthalene counterparts. Nevertheless, some of the biphenyl derivatives investigated are predicted to have anion affinities larger than those measured for SbF₅, which is considered one of the strongest anion capturers. Therefore, although weaker than their naphthalene analogs, the 2,2'-diBeX-1,1'-biphenyl derivatives can still be considered powerful anion sponges. This study supports the idea that compounds containing -BeX groups in chelating positions behave as anion sponges due to the electron-deficient nature and consequently high intrinsic Lewis acidity of these groups. Graphical Abstract Compounds containing -BeX groups in chelating positions, such as 2,2'-diBeX-1,1'-biphenyl (X = H, F, Cl, CN) derivatives, behave as anion sponges due to the electron-deficient nature of these groups.