Boron rings containing planar octacoordinate iron and cobalt

The boron rings containing planar octacoordinate transition metals, D (8h) FeB8 (2-), CoB8 (-) and CoB8 (3+), C (2v) FeB8, D (2h) CoB8 (+) and CoB8, are optimized with all real vibrational frequencies at the B3LYP/6-311+G* level of the theory. The D (8h) FeB8 (2-) and CoB8 (-) isomers are global minima, while D (8h) CoB8 (3+) is only local minimum. The electronic structure character of these systems is revealed by natural bond orbital (NBO) analysis, showing that the boron rings containing planar octacoordinate transition metals have stability and aromaticity with six pi electrons. The aromaticity is confirmed by nucleus independent chemical shifts (NICS) calculations.