Planar dicyclic B6S6, B6S6-, and B6S62- clusters: Boron sulfide analogues of naphthalene

Abstract

Inorganic analogues of hydrocarbons or polycyclic aromatic hydrocarbons (PAHs) are of current interest in chemistry. Based upon global structural searches and B3LYP and CCSD(T) calculations, we present herein the perfectly planar dicyclic boron sulfide clusters: D2h B6S6 (1, 1Ag), D2h B6S6- (2, 2B3u), and D2h B6S62- (3, 1Ag). These are the global minima of the systems, being at least 0.73, 0.81, and 0.53 eV lower in energy, respectively, than their alternative isomers at the CCSD(T) level. The D2h structures feature twin B3S2 five-membered rings, which are fused together via a B2 unit and terminated by two BS groups. Bonding analyses show that the closed-shell B6S62- (3) cluster possesses 10 delocalized π electrons, closely analogous to the bonding pattern of the aromatic naphthalene C10H8. The B6S6- (2) and B6S6 (1) species are readily obtained upon removal of one or two π electrons from B6S62- (3). The results build a new analogous relationship between boron sulfide clusters and their PAH counterparts. The B6S6- (2) monoanion and B6S62- (3) dianion can be effectively stabilized in neutral LiB6S6 and Li2B6S6 salts, respectively.