AbstractLanthanide (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.
Monovalent lanthanide(I) in borozene complexes
