Three-Center Bonds in closo -Sb 2 Sn 10 Clusters

Using the DFT PBE0 method, bond indices were calculated, and localization of orbitals in the p-, m-, and o-Sb2Sn10 clusters was established. The KSnSnSn indices (0.31–0.41) are larger than the KSnSbSn indices (0.28–0.31); ISnSn ≤ 0.48, ISbSn ≤ 0.50, and ISbSb ≤ 0.59. The distorted icosahedral cluster is stabilized by thirteen bonding electron pairs filling 20 orbitals localized near triangular faces. The occupancies of the three-center orbitals vary within 1.91–1.97. Each atom retains a lone electron pair. The tin valence (2.43–2.57) exceeds the number of valence-active electrons but is less than the coordination number. The antimony valence (2.80–2.81) corresponds to the number of the valence-active electrons. Energy increases in the p- < m- < o-isomer series.