Theoretical study of structure and migration nonrigidity of closo-boranes B6H7- and LiB6H7

Nonempirical (SCF) calculations of closo-borate anion B6H7 and its salt LiB6H7 with optimization of geometry for different alternative structures are carried out. Structures (t) and (tt) with cations over the face and over the pair of opposite faces are found to be more profitable for the B6H7- anion and its salt LiB6H7, correspondingly. Structures (b) and (bb) with cations over the edge for B6H7- and over the pair of opposite edges for LiB6H7 correspond to the top of a migration barrier. The hmigr value is approximately 10 kcal for B6H7- and approximately 21 kcal for LiB6H7. Migration with proton exchange is possible for B6H7-. Geometric deformation polarization of electron density and splitting of degenerated energy levels εi of the B6H72- anion under H+ and Li+ effect are studied. Alkali cation is found to deform and polarize weakly the B6H72- skeleton