Realization of an Al≡Al Triple Bond in the Gas‐Phase Na₃Al₂⁻ Cluster via Double Electronic Transmutation

Abstract

The discovery of homodinuclear multiple bonds composed of Group 13 elements represents one of the most challenging frontiers in modern chemistry.Aclassical triple bond such as NNand HCCH contains one s bond and two p bonds constructed from the porbitals perpendicular to the s bond. However,the traditional textbook triple bond between two Al atoms has remained elusive.H ere we report an Al Al triple bond in the designer Na 3 Al 2 À cluster predicted in silico, which was subsequently generated by pulsed arc discharge followed by mass spectrometry and photoelectron spectroscopy characterizations.Being effectively Al 2À due to the electron donation from Na, the Al atoms in Na 3 Al 2 À undergo adouble electronic transmutation into Group 15 elements,t hus the Al 2À Al 2À kernel mimics the P Pa nd N Nm olecules.W e anticipate this work will stimulate more endeavors in discovering materials using Al 2À Al 2À as abuilding blocki nt he gas phase and in the solid state.

The Search for Enhanced σ‐Donor Ligands to Stabilize Boron‐Boron Multiple Bonds

“…To stabilize compounds with BB multiple bonds, it is necessary to fill the empty 2p z orbital on each boron atom using a σ‐donor ligand that donates an electron pair (see Figure 1). [2,25,26,29–38] Another strategy to stabilize group 13 multiple bonding is through electronic transmutation as used by Boldyrev, Bowen, and Zhang [39–41] …”

Boron‐Made N2: Realization of a B≡B Triple Bond in the B2Al3− Cluster

“…More recently, our group reported an Al≡Al triple bond in the Al2Na3cluster in which the Al2 4moiety is both isoelectronic and isostructural to the P≡P molecule. [7] Compared to the relatively devoid research on the Ga≡Ga and Al≡Al triple bonds, it has been fruitful for B≡B. The first example was a molecule OC→B≡B←CO isolated in an argon matrix at 8 K by Zhou et al, [8] which further triggered copious theoretical and experimental studies on the B2 kernel stabilized by other ligands such as NHC (N-heterocyclic carbene), diatomic molecules (CO, CS, N2, BO -), and phosphine derivatives (PCl3, PMe3).…”

“…Previously, this strategy [26] has been successfully applied for the prediction of many new compounds, which were experimentally observed afterwards. While the enrichment of each Al atom by two extra electrons was previously used to design a triple Al≡Al in Na3Al2cluster, [7] its application to B species has not yet been reported, and remains intriguing especially due to significantly smaller atomic radius.…”

“…For instance, relaxed FCs of Na3Al2 -(0.95) and Na4Al2 (1.08), both having Al≡Al triple bonds, are lower than the relaxed FC responsible for stretching mode (1.43) in RR'Al=AlRR' molecule. 7 Obviously, the atomic environment of the bond affects FC tremendously, and, for instance, bulky ligands (as in RR'Al=AlRR') can significantly strengthen the bond. On the contrary, the B≡B skeleton in B2Al3acquires extra electrons, thus increasing the Coulomb repulsion.…”

“…As a consequence, we should expect elongation of the bond and decrease of the FC. For the detailed discussion regarding the relaxed FCs, refer to a recent article by Zhang et all 7 and SI where this discussion is deepened alongside with some notes about the bond dissociation energy.…”