BeBe triple bond in Be2X4Y2 clusters (X = Li, Na and Y = Li, Na, K) and a perfect classical BeBe triple bond presented in Be2Na4K2

Herein, we presented a series of Be2X4Y2 clusters (X = Li, Na and Y = Li, Na, K) containing BeBe triple bonds, which were constructed by six alkali metals as electron-donating ligands. By virtue of the electrostatic potential mapping of the precedent BeBe double-π bonded D4h-Be2X4 clusters, the Be2X4Y2 trans-bent geometries and the BeBe triple bonds inside were both well interpreted. More remarkably, we first identified a perfect classical BeBe triple bond in D4h-Be2Na4K2 and its Wiberg bond index of Be–Be (WBIBe–Be) reached up to 2.43. Meanwhile, our strategy provides a new approach to explain the trans-bent structure caused by terminal coordination.