Unusually Short Be−Be Distances with and without a Bond in Be₂F₂and in the Molecular Discuses Be₂B₈and Be₂B₇⁻

Abstract

Quantum‐chemical calculations at the CCSD(T)/cc‐pVTZ level of theory show that beryllium subfluoride, Be2F2, has a bond dissociation energy of De=76.9 kcal mol−1, which sets a record for the strongest Be−Be bond. The synthesis of this molecule should thus be possible in a low‐temperature matrix. The discus‐shaped species Be2B8 and Be2B7− possess the shortest Be–Be distance for a molecule in the electronic ground state, but there is no Be−Be bond. The cyclic species Be2B8 and Be2B7− exhibit double aromaticity with 6σ and 6π electrons, which strongly bind the Be2 fragment to the boron atoms. The very short interatomic distance between the beryllium atoms is due to the Be−B σ and π bonds, which operate like spokes in a wheel pressing the beryllium atoms together. The formation of the Be−B bonds has effectively removed the electronic charge of the valence space between the beryllium atoms. Along the Be–Be axis, there are two cage critical points adjacent to a ring critical point at the midpoint, but there is no bond critical point and no bond path.

A Very Short Be–Be Distance but No Bond: Synthesis and Bonding Analysis of Ng–Be2O2–Ng′ (Ng, Ng′=Ne, Ar, Kr, Xe)

“…Ta ble 2 showst hat the bond orderP (BeÀBe) has av alue of 0.08 in all complexes NgÀBe 2 O 2 ÀNg'.T his is much smaller than in diatomic Be 2 which has ac alculated equilibrium distance of 2.534 (experimentally 2.453 ) [22] but ab ond order of 0.38. [9] The very polar BeÀOb onds in the complexes NgÀBe 2 O 2 ÀNg' have auniform bond order of P(BeÀO) = 0.54.…”

“…After this study was completed, at heoretical work was published in continuationo fo ur earlier study of Be 2 B 8 and Be 2 B 7 À , [9] which reports very short BeÀBe distances between 1.728-1.866 in molecules with ar hombic Be 2 X 2 core (X = C, N). [23] The molecules have not been observed so far.L ately, at heoreticals tudy analyzed the bondings ituation of Be 2 O 2 .…”

“…The full sets of geometrical data are given in the SupportingI nformation, Table S1. tally still unknown discus-shaped speciesB e 2 B 8 andB e 2 B 7 À , which were calculated with BeÀBe distances between 1.901-1.910 . [9] The observed compounds NgÀBe 2 O 2 ÀNg' have much shorter BeÀBe distances.…”

Electronic and structural properties of Lin@Be2B8 (n = 1–14) and Lin@Be2B36 (n = 1–21) nanoflakes shed light on possible anode materials for Li‐based batteries

“…Boron rich materials, eventually doped with electron poor elements, provide promising category for inorganic electrides although available information is scarce. Frenking and coworkers have investigated the interaction between Be 2 and the B 8 cluster with D 7h structure and found a stable Be 2 B 8 species with D 8h symmetry . Comparing Be 2 B 8 (D 8h ) to B 8 (D 7h ) reveals the role of the two Be atoms.…”

“…Comparing Be 2 B 8 (D 8h ) to B 8 (D 7h ) reveals the role of the two Be atoms. The presence of the Be atoms decrease B–B distances, increase chemical and thermal stability as well as aromatic character of atomic ring and thus provide room for atoms or electrons trapping . In addition, the Be 2 B 8 species constitutes the first example where very short Be–Be distance and the absence of bond path along Be–Be axis lead simultaneously to a local energy minimum in the potential energy surface (PES).…”