In their paper ‘Noncovalent interaction of chemical bonding between alkaline earth cations and benzene?’ (Chem. Phys. Lett.,2001, 349, 113), X.J. Tan and co-workers carried out theoretical calculations of complexes formed between beryllium, magnesium, and calcium ions and benzene. To which orbital interactions were the binding of the alkali metal to benzene attributed? How was the C–C bond length in benzene affected by this interaction? Place the M–C bonds in order of increasing bond enthalpy. How did the strength of the bonds compare to those formed between Group 1 elements and benzene? Sketch the geometry of the metal–benzene complexes.