CB₁₁S₃⁺: A Triangular Boron-Based Cluster with One Planar Tetracoordinate Carbon at Its Edge

Boron-based clusters containing planar tetracoordinate carbon (ptC) are unique and scarce. Isoelectronic-replacing after proper vulcanization is an effective strategy to obtain the ptC based on the B12 cluster. Herein we report computational evidence for a ternary CB11S3+ (C2v, 1A1) cluster, which possesses a concentric double-triangle structure containing one ptC atom at the peripheral edge. The unbiased structural explorations of potential energy surfaces and high-level CCSD(T) calculations indicate that the ptC CB11S3+ cluster is a true global minimum. Born−Oppenheimer molecular dynamics (BOMD) simulations reveal that it is dynamically stable against isomerization and decomposition. Chemical bonding analysis reveals that three delocalized π bonds endow the π aromaticity to the CB11 unit of CB11S3+. In addition, the strong S → B π back-bonding is also conducive to the stability of CB11S3+. The current findings offer opportunities for further boron-based ptC clusters.