### Observation of highly stable and symmetric lanthanide octa-boron inverse sandwich complexes.

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**ABSTRACT**: While boron forms a wide range of metal borides with important industrial applications, there has been relatively little attention devoted to lanthanide boride clusters. Here we report a joint photoelectron spectroscopy and quantum chemical study on two octa-boron di-lanthanide clusters, Ln_{2}B_{8}^{-} (Ln = La, Pr). We found that these clusters form highly stable inverse sandwich structures, [Ln-B_{8}-Ln]^{-}, with strong Ln and B_{8} bonding via interactions between the Ln 5d orbitals and the delocalized σ and π orbitals on the B_{8} ring. A (d-p)δ bond, involving the 5dδ and the antibonding π orbital of the B_{8} ring, is observed to be important in the Ln-B_{8} interactions. The highly symmetric inverse sandwich structures are overwhelmingly more stable than any other isomers. Upon electron detachment, the (d-p)δ orbitals become half-filled, giving rise to a triplet ground state for neutral La_{2}B_{8} In addition to the two unpaired electrons in the (d-p)δ orbitals upon electron detachment, the neutral Pr_{2}B_{8} complex also contains two unpaired 4f electrons on each Pr center. The six unpaired spins in Pr_{2}B_{8} are ferromagnetically coupled to give rise to a septuplet ground state. The current work suggests that highly magnetic Ln…B_{8}…Ln inverse sandwiches or 1D Ln…B_{8}…Ln nanowires may be designed with novel electronic and magnetic properties.

**PROVIDER: **S-EPMC6064993 | BioStudies |

**REPOSITORIES: ** biostudies

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