Be&z.tbd;Be triple bond in BeXY clusters (X = Li, Na and Y = Li, Na, K) and a perfect classical Be&z.tbd;Be triple bond presented in BeNaK

Herein, we presented a series of Be 2 X 4 Y 2 clusters (X = Li, Na and Y = Li, Na, K) containing Be&z.tbd;Be triple bonds, which were constructed by six alkali metals as electron-donating ligands. By virtue of the electrostatic potential mapping of the precedent Be&z.dbd;Be double-π bonded D 4h -Be 2 X 4 clusters, the Be 2 X 4 Y 2 trans -bent geometries and the Be&z.tbd;Be triple bonds inside were both well interpreted. More remarkably, we first identified a perfect classical Be&z.tbd;Be triple bond in D 4h -Be 2 Na 4 K 2 and its Wiberg bond index of Be-Be (WBI Be-Be ) reached up to 2.43. Meanwhile, our strategy provides a new approach to explain the trans -bent structure caused by terminal coordination. The trans -bent Be 2 X 4 Y 2 structures are explained through ESP of Be 2 X 4 and a perfect Be&z.tbd;Be triple bond is confirmed in D 4h -Be 2 Na 4 K 2 .