Probing the Structures and Lanthanum–Lanthanum Bonding in La<sub>2</sub>B<sub><i>n</i></sub><sup>–</sup> (<i>n</i> = 4–6) Clusters
Jordan Burkhardt, Teng‐Teng Chen, Weijia Chen, Dao-Fu Yuan, Wan‐Lu Li, Lai‐Sheng Wang
Abstract
We report an investigation on the structures and chemical bonding in a series of di-lanthanum boron clusters, La 2 B n – ( n = 4–6), using photoelectron spectroscopy and theoretical calculations. Well-resolved photoelectron spectra are obtained and used to verify the global minima of the lanthanide boron clusters. The structures of La 2 B 4 – and La 2 B 5 – are found to consist of open B 4 and B 5 rings, respectively, around the La 2 dimer equatorially. Theoretical evidence of La–La σ bonding is obtained in La 2 B 4 –, whereas the bonding in La 2 B 5 – is similar to that of an incomplete inverse sandwich without real La–La bonding. The global minimum of La 2 B 6 – is completely different, where one of the La atoms can be viewed as substituting a B atom of the B 7 cluster due to the high electronic stability of the B 7 3– borozene. The resulting lanthaborozene [LaB 6 ] 3– forms a half-sandwich structure with the second La atom, with evidence of La–La σ bonding. Lanthanide–lanthanide bonds are relatively rare in chemistry. The current work suggests that binary lanthanide boron clusters provide interesting systems to study lanthanide–lanthanide bonding.