A B 2-Ta@B 18 − tubular molecular rotor and a Ta@B 20 − boron drum with the record coordination number of twenty were observed via a joint experimental and theoretical investigation.
A tubular molecular rotor B 2-Ta@B 18 − ( 1) and boron drum Ta@B 20 − ( 2) with the highest coordination number of twenty in chemistry are observed via a joint photoelectron spectroscopy and first-principles theory investigation.