Structure and bonding properties of the platinum-mediated tetrametallic endohedral fullerene La₃Pt@C₉₈

Nowadays, focus is on encapsulating a greater variety and amount of metal species into fullerene cages due to their diverse structures and fascinating properties. Nevertheless, the encapsulation of more positively charged metal atoms inside one cage means more Coulomb repulsion, which makes the formation of such endohedral metallofullerenes (EMFs) difficult. In general, non-metallic atoms such as N and O should be introduced as mediators for the formation of trimetallic or tetrametallic endohedral fullerenes. However, it is still unknown whether metal atoms can serve as mediators themselves to form such EMFs. In this paper, the endohedral tetrametallic fullerene La₃Pt@C₉₈ with the platinum atom as a metallic mediator is reported. The EMFs of La₃Pt@C₂ (2n = 98-300) were generated by the method of laser ablation in the gas phase and verified by mass spectrometry. Among them, the EMF of La₃Pt@C₉₈ was selected and studied by theoretical calculations. Results show that the two most stable isomers are La₃Pt@C₂(231010)-C₉₈ and La₃Pt@C₁(231005)-C₉₈. For both of them, the inner La₃Pt metallic cluster appears in a pyramidal shape, different from the planar triangular pattern of La₃N clusters previously reported. Further calculations prove the existence of encaged La-Pt bonds in the La₃Pt cluster. It was also revealed that the negatively charged Pt atom is situated near the center of the four-center two-electron (4c-2e) metal bond with the highest occupancy number. The platinum-mediated cluster stabilizes the EMFs greatly, promising the possibility of synthesizing new species of Pt-containing EMFs.