PrB7- : A Praseodymium-Doped Boron Cluster with a Pr-II Center Coordinated by a Doubly Aromatic Planar eta(7)-B-7(3-) Ligand

摘要

The structure and bonding of a Pr-doped boron cluster (PrB7-) are investigated using photoelectron spectroscopy and quantum chemistry. The adiabatic electron detachment energy of PrB7- is found to be low [1.47(8) eV]. A large energy gap is observed between the first and second detachment features, indicating a highly stable neutral PrB7. Global minimum searches and comparison between experiment and theory show that PrB7- has a half-sandwich structure with C-6v symmetry. Chemical bonding analyses show that PrB7- can be viewed as a Pr-II[eta(7)-B-7(3-)] complex with three unpaired electrons, corresponding to a Pr (4f(2)6s(1)) open-shell configuration. Upon detachment of the 6s electron, the neutral PrB7 cluster is a highly stable Pr-III[eta(7)-B-7(3-)] complex with Pr in its favorite + 3 oxidation state. The B-7(3-) ligand is found to be highly stable and doubly aromatic with six delocalized pi and six delocalized s electrons and should exist for a series of lanthanide M-III[eta(7)-B-7(3-)] complexes.