Fluxional Bonds in Planar B19−, Tubular Ta@B20−, and Cage‐Like B39−

: Based on detailed bonding analyses on the fluxional behaviors of planar B19- , tubular Ta@B20- , and cage-like B39- , we propose the concept of fluxional bonds in boron nanoclusters as an extension of the classical localized bonds and delocalized bonds in chemistry. © 2018 Wiley Periodicals, Inc.