Ultra‐Weak Metal−Metal Bonding: Is There a Beryllium‐Beryllium Triple Bond?

Abstract

Metal‐metal triple bonds featuring s‐block element have not been reported until now. Only Be−Be double bonds between have been predicted theoretically based on the intuitive electron donation from four s1 type electron‐donating ligands. Herein, we theoretically predicted a novel species featuring a Be−Be triple bond in the Li6Be2 molecule. The molecule was found to be thermodynamically stable. The presence of the triple bond was confirmed by adaptive natural density partitioning (AdNDP), electron localization function (ELF), and atoms in molecules (AIM) analyses. Moreover, the mechanical strength of the Be−Be triple bond was analyzed by using compliance matrix, pointing towards its ultra‐weak nature.

Nature of the chemical bonding inD3h[MH3M]+cations (M = Be, Mg)

“…We note that Liu et al have interpreted the bonding in the octahedral Be 2 (μ 2 ‐Li) 4 cluster, and others, in terms of a Be=Be double‐π bond and the bonding in Be 2 X 4 Y 2 clusters (X = Li, Na and Y = Li, Na, K) in terms of Be≡Be triple bonds . Calculations and analysis carried out by Rohman et al also support the notion of Be≡Be triple bonds in various systems, including Be 2 X 6 (X = Li, Na), but they found the BeBe bonding to be ultraweak in spite of the very short BeBe distances . Indeed, some systems have been studied both experimentally and computationally, such as the rhombic Be 2 O 2 cluster, which feature very short BeBe distances in the absence of any direct BeBe chemical bonding …”

“…In spite of the obvious deterrence for experimentalists of the high toxicity of beryllium compounds, a great deal is now known about the organometallic and coordination chemistry of beryllium . Beryllium compounds that have been studied experimentally and especially computationally include various systems that feature BeBe bonding and/or very short BeBe distances . For example, it has been shown for various choices of X, such as a fluorine atom or an appropriate N‐heterocyclic carbene ligand, that certain XBeBeX species feature Be−Be bonds that are both significantly stronger and shorter than the weak and rather long bond in Be 2 .…”

From Very Strong to Inexistent Be−Be Bonds in the Interactions of Be2with π‐Systems

“…It can be also observed that the BeÀ Be distances are around 2 Å, and therefore rather similar to the ones reported previously in the literature [7][8][9][10][11][12][13][14] for different complexes involving Be 2 , including those cases in which the BeÀ Be interaction was found to be significantly strong. However, a detailed analysis of the bonding and the orbitals of the complexes in Figure 1 indicates that the two Be atoms are covalently bonded to the carbon atoms of the two C n H n moieties; but no BeÀ Be bonding interaction is detected.…”

“…[9] More recently, it was claimed that BeÀ Be double π-bonds were behind the strength of the BeÀ Be interaction in Be 2 (μ 2 -X) 4 (X=Li, Cu, BeF) octahedral clusters, [10] and that BeÀ Be triple bonds could be found in Li 6 Be 2 molecule. [11] In a similar context, it was also showed that the insertion of Be in beryllocene (C 5 H 5 À BeÀ C 5 H 5 ) to yield the corresponding binuclear metallocene (C 5 H 5 À Be 2 À C 5 H 5 ) is rather exothermic (274.9 kJ • mol À 1 ), indicating that the BeÀ Be interaction is strongly stabilizing. [12] Similar results were found when cyclopentadiene was replaced by its P-containing derivative, the phosphole radical (η 5 -C 4 H 4 P * ), [13] and in multimetallocenes.…”

In Silico Search for Boron‐Beryllium Dative Bond

“…The Chemistry of Be needs attention due to its toxicity. Therefore, the search for safer Be containing compounds is very essential which is gaining importance both theoretically and experimentally . The first example of transition metal Be dative bond in [(PCy 3 ) 2 Pt–BeCl 2 ] and [(PCy 3 ) 2 Pt–BeCl(CH 3 )] have recently been synthesized which suggest the Lewis acidity of BeCl 2 .…”