Realization of an Al≡Al Triple Bond in the Gas‐Phase Na ₃ Al ₂ ⁻ Cluster via Double Electronic Transmutation

The discovery of homodinuclear multiple bonds composed of Group 13 elements represents one of the most challenging frontiers in modern chemistry. A classical triple bond such as N≡N and HC≡CH contains one σ bond and two π bonds constructed from the p orbitals perpendicular to the σ bond. However, the traditional textbook triple bond between two Al atoms has remained elusive. Here we report an Al≡Al triple bond in the designer Na 3 Al 2 − cluster predicted in silico, which was subsequently generated by pulsed arc discharge followed by mass spectrometry and photoelectron spectroscopy characterizations. Being effectively Al 2− due to the electron donation from Na, the Al atoms in Na 3 Al 2 − undergo a double electronic transmutation into Group 15 elements, thus the Al 2− ≡Al 2− kernel mimics the P≡P and N≡N molecules. We anticipate this work will stimulate more endeavors in discovering materials using Al 2− ≡Al 2− as a building block in the gas phase and in the solid state.