Monovalent lanthanide(I) in borozene complexes

Wan-Lu Li,Teng-Teng Chen,Lai-Sheng Wang,Wei-Jia Chen,Jun Li

doi:10.1038/s41467-021-26785-9

Abstract

Lanthanide (Ln) elements are generally found in the oxidation state +II or +III, and a few examples of +IV and +V compounds have also been reported. In contrast, monovalent Ln(+I) complexes remain scarce. Here we combine photoelectron spectroscopy and theoretical calculations to study Ln-doped octa-boron clusters (LnB8−, Ln = La, Pr, Tb, Tm, Yb) with the rare +I oxidation state. The global minimum of the LnB8− species changes from Cs to C7v symmetry accompanied by an oxidation-state change from +III to +I from the early to late lanthanides. All the C7v-LnB8− clusters can be viewed as a monovalent Ln(I) coordinated by a η8-B82− doubly aromatic ligand. The B73−, B82−, and B9− series of aromatic boron clusters are analogous to the classical aromatic hydrocarbon molecules, C5H5−, C6H6, and C7H7+, respectively, with similar trends of size and charge state and they are named collectively as “borozenes”. Lanthanides with variable oxidation states and magnetic properties may be formed with different borozenes.

Highlights

Lanthanide (Ln) elements are generally found in the oxidation state +II or +III, and a few examples of +IV and +V compounds have been reported
The B73−, B82−, and B9− series of aromatic boron clusters are analogous to the classical aromatic hydrocarbon molecules, C5H5−, C6H6, and C7H7+, respectively, with similar trends of size and charge state and they are named collectively as “borozenes”
The Oxidation state (OS) of lanthanide elements has been of particular interest because it is directly related to the unique chemical, magnetic, and optical properties of lanthanide compounds[2,3]

Summary

Introduction

Lanthanide (Ln) elements are generally found in the oxidation state +II or +III, and a few examples of +IV and +V compounds have been reported. The photoelectron spectra of PrB8− are almost identical to those of LaB8− (Fig. 1 and Supplementary Fig. 2); the observed spectral features and their binding energies are given in Supplementary Table 2, along with the calculated values. For the late lanthanide LnB8− (Ln = Tb, Tm, Yb), the half-sandwich C7v structure is found to be the global minimum at all levels of theory, with high stabilities over other isomers (Fig. 2c and Supplementary Fig. 4).

Results

Conclusion