Observation of a metal-centered B₂-Ta@B₁₈⁻tubular molecular rotor and a perfect Ta@B₂₀⁻boron drum with the record coordination number of twenty

Abstract

A tubular molecular rotor B₂-Ta@B₁₈^- (1) and boron drum Ta@B₂₀^- (2) with the highest coordination number of twenty in chemistry are observed via a joint photoelectron spectroscopy and first-principles theory investigation.