Vacancy-Induced Atomic Diffusion in a Molecular Metal Cluster Complex

The presence of atomic vacancies in a close-packed material is believed to allow the migration of atoms adjacent to the vacancies, which induces dynamics of atoms. However, it is not known whether atoms in discrete molecules can undergo vacancy-induced dynamics. We describe herein the generation of a close-packed Pd₁₂ cluster complex [Pd₁₂(C₇H₇)₆][B(Ar^F)₄]_n (n = 2, 3) with a Pd-atom vacancy, and the observation of the diffusion of Pd atoms. Variable-temperature NMR analysis, X-ray structure analysis, and theoretical calculations indicate that an atomic vacancy is located at the surface sites of the Pd₁₂ core, and that it migrates rapidly on the NMR timescale. This means that all 11 palladium atoms at the surface undergo self-diffusion with a low energy barrier. These results demonstrate, for the first time, that atomic diffusion occurs within a molecule through the vacancy mechanism.