“Giant” Gyroscope‐Like Molecules Consisting of Dipolar Cl‐Rh‐CO Rotators Encased in Three‐Spoke Stators That Define 25–27‐Membered Macrocycles

Yet another feat for the Grubbs catalyst: Reactions with 1 a,b followed by hydrogenations give 2 a,b. The sizeable cavities of 2, which were characterized crystallographically, allow for rapid Cl-Rh-CO rotation in solution. Reactions with ArCCLi give ArCC–Rh–CO species; when the aryl group is sufficiently large, it is confined between two macrocycles, blocking rotation.