Boron rings containing planar octa-and enneacoordinate cobalt,iron and nickel metal elements

For a series of boron rings with planar hyper-coordinate 8th group transition metal atoms, singlet ¹FeB₈⁻², multiplet ^k FeB₉ ⁿ (n = −1, k = 1; n = 0, k = 2), singlet ¹CoB₈ ⁿ (n = −1, +1, +3), multiplet ^k CoB₉ ⁿ (n = +1, k = 2; n = 0, k = 1) and singlet ¹NiB₉⁺, the geometry structures have been optimized to be local minima on corresponding potential hyper-surfaces. The electron structures are discussed by orbital analysis and the aromaticity is predicted by nucleus-independent chemical shifts calculation at both the B3LYP/6-311+G^* and BP86/6-311+G^* levels of theory, respectively. The results suggest that all these structures with high symmetry planar geometries are stable and have aromatic properties with six π valence electrons. Supported by the Research Fund for the Doctoral Program of Higher Education (Grant No. 20070533142) and the China Postdoctoral Science Foundation (Grant No. 20070410139)