Beryllium Bonds, Do They Exist?

Abstract

The complexes between BeX2 (X = H, F, Cl, OH) with different Lewis bases have been investigated through the use of B3LYP, MP2, and CCSD(T) approaches. This theoretical survey showed that these complexes are stabilized through the interaction between the Be atom and the basic center of the base, which are characterized by electron densities at the corresponding bond critical points larger than those found in conventional hydrogen bonds (HBs). Actually, all bonding indices indicate that, although these interactions that we named "beryllium bonds" are in general significantly stronger than HBs, they share many common features. Both interactions have a dominant electrostatic character but also some covalent contributions associated with a non-negligible electron transfer between the interacting subunits. This electron transfer, which in HBs takes place from the HB acceptor lone-pairs toward the σYH* antibonding orbital of the HB donor, in beryllium bonds goes from the lone pairs of the Lewis base toward the empty p orbital of Be and the σBeX* antibonding orbital. Accordingly, a significant distortion of the BeX2 subunit, which in the complex becomes nonlinear, takes place. Concomitantly, a significant red-shifting of the X-Be-X antisymmetric stretching frequencies and a significant lengthening of the X-Be bonds occur. The presence of the beryllium bond results in a significant blue-shifting of the X-Be-X symmetric stretch.

Revisiting the beryllium bonding interactions from energetic and wavefunction perspectives

“…Recently, Manuel Yáñez et al [17][18][19][20][21][22][23] has substantiated the existence of another kind of noncovalent weak interactions, namely, beryllium bonds, which may have some significant implications in different fields. It is well established that the association of beryllium fluoride to ADP inhibits protein action.…”

“…[31,32] Hence, it is of paramount importance to have a clear understanding of the nature of Be bonds and provide alternative mechanisms to beryllium toxicity. The bonding of the systems under scrutiny has been carefully analyzed [17] by means of three different approaches, namely the quantum theory of atoms in molecules (QTAIM), [33] the electron localization function (ELF) theory, [34,35] and the natural bond orbital (NBO) method. [36] Nevertheless, one point to mention is that all these three methods have its underpinnings in wavefunction theory, which is solely one side of the coin, the eigenfunction of the Schrödinger equation.…”

Interplay of Hydrogen, Halogen, Lithium and Beryllium Bonds in Complexes of Thiirane

“…. .Y [63][64][65]. The Be atom, like H and Li, is also highly electropositive and therefore the interaction energies of beryllium bonds tend to have a substantial electrostatic component and are generally comparable in strength to very strong hydrogen bonds.…”

“…Electronic charge may also be transferred into the A-Be/A -Be antibonding orbital (σ * A-Be/A -Be ). The shift in charge densities greatly increase the covalent character of beryllium bonds [63,64] and may result in relatively high ρ bcp for these bonds compared to their hydrogen-bonded analogues [63].…”

“…It may also lead to substantial changes in the electron density of the Lewis base to the extent that the acidity of the base increases [63,65].…”