Trapping One Electron between Three Beryllium Atoms: Very Strong One-Electron Three-Center Bonds

The ability of a set of beryllium-substituted cyclohexane derivatives to trap electrons was determined by evaluating their electron affinities at the G4(MP2) level of theory. The nature of bonding and the effect of the different substituents attached to beryllium were studied by different computational methods (quantum theory of atoms in molecules, electron localization function, natural bond orbital, and analysis of the spin density), revealing the existence of a one-electron/Be₃ cyclic bonding in trisubstituted species. This peculiar bond is the key for the high electron affinity values found in the tri-BeX derivatives (X=F, Cl, CN), such as the triberyllium cyano derivatives of cyclohexane, reaching values of 294 kJ mol^-1 , only marginally smaller than the values reported for tetracyanoethylene (305 kJ mol^-1 ) and for some fullerenes (306 kJ mol^-1 ).