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Cyclic Boron Clusters Enclosing Planar Hypercoordinate Cobalt, Iron, and Nickel

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journal contribution
posted on 01.12.2008, 00:00 by Keigo Ito, Zhifeng Pu, Qian-Shu Li, Paul von Ragué Schleyer
Planar cyclic boron clusters with cobalt, iron, and nickel atoms at their centerssinglet D8h CoB8, D9h FeB9, CoB9, and NiB9+are computed to be stable minima at the BP86/TZVPP DFT level. Stochastic searches of the singlet and triplet potential energy surfaces show the planar hypercoordinate D8h CoB8 (1) and D9h FeB9 (2) singlet isomers to be the global minima. Their double aromatic character with 6 π and 10 radial electrons is documented by detailed NICSzz grid and CMO-NICSzz analyses at PW91/TZVPP. These results encourage gas phase investigations of these two exotic anions. Although isoelectronic with D9h FeB9 (2), CoB9 and NiB9+ prefer nonplanar structures, triplet 3-aT for the former and singlet 4-a for the latter.