Beryllepin, C6H6Be, and "Beryllium-Inserted Benzenes," C6H6Ben, n=2-6: A Density Functional Computational Investigation

The seven-membered berylliumcontaining heterocycle beryllepin, C6H6Be, has been examined computationally at the B3LYP/6-311++G** density functional level of theory. Beryllepin is best described as a planar singlet heterocyclic conjugated triene with marginal aromatic character containing a C-Be-C moiety forced to be nonlinear (<C-Be-C = 146.25 degrees) by the cyclic constraints of the seven-membered ring. The molecule can be considered to be derived from a benzene-like system in which a neutral beryllium atom has been inserted between two adjacent carbon atoms. The 11 other possible "beryllium-inserted benzenes," C(6)H(6)Ben, n = 2-6, have also been investigated. Only two of these heterocyclic systems, the eight-membered 1,4-diberyllocin and the nine-membered 1,4,7-triberyllonin, were found to be stable, singlet-ground-state systems, albeit with little aromatic character. Of the remaining nine beryllium-inserted benzenes, with the exception of the 11-membered ring containing five beryllium atoms and the 12-membered ring containing six beryllium atoms, which were calculated to exist as a ground state pentet and septet, respectively, all were calculated to be ground state triplet systems. (C) 2015 Wiley Periodicals, Inc.