A theoretical study on the stability difference of the borane B n H n 2 − and carborane C 2 B n −2 H n (5 ≤ n ≤ 7) clusters

In order to study the electronic structure and structural stability of boraneB n H n 2 −and carborane C 2 B n −2 H n (5 ≤  n  ≤ 7) clusters, especially the stability difference between the boraneB 5 H 5 2 −and carborane C 2 B 3 H 5 . The frontier orbital energy levels of the boraneB n H n 2 −and carborane C 2 B n −2 H n (5 ≤  n  ≤ 7) clusters are calculated at CCSD(T)/aug‐cc‐pVXZ//B3LYP/def2‐TZVPP level. The results are further analyzed by qualitative frontier orbital method based on the cap–ring interaction. The results reveal that: (1) the larger E gap (HOMO‐LUMO energy gap) of carborane C 2 B n −2 H n (5 ≤  n  ≤ 7) clusters than boraneB n H n 2 −(5 ≤  n  ≤ 7) clusters originates from the more effective cap–ring orbital overlap of carborane C 2 B n −2 H n (5 ≤  n  ≤ 7) clusters than that of boraneB n H n 2 −(5 ≤  n  ≤ 7) clusters; (2) the smallest E gap of the boraneB 5 H 5 2 −results from the highest energy level of the ring symmetry‐adapted linear combination orbital ofB 5 H 5 2 −cluster; and (3) the largest E gap of the carborane C 2 B 3 H 5 is induced by the most effective cap–ring orbital interaction of C 2 B 3 H 5 cluster. © 2014 Wiley Periodicals, Inc.