A chiral [2]catenane self-assembled from meso-macrocycles of palladium(II)

Reaction of trans-PdX2(SMe2)2](X = Cl or Br) with the chiral ligand LL = 1,1'-binaphthyl-2,2'-(NHC(= O)-3-C5H4N)2 gave the 2]catenane complexes trans-{(PdX2)2(micro-LL)2}2], which are formed by self-assembly from 4 units each of trans-PdX2 and LL. The catenation is favored by the formation of multiple hydrogen bonds between the constituent macrocycles (4 x NHClPd, 2 x NHO double bond C). If the ligand LL is racemic, each macrocycle trans-(PdX2)2(micro-LL)2] is formed in the meso form trans-(PdX2)2(micro-R-LL)(micro-S-LL)] but the resulting 2]catenane is chiral as a direct result of the catenation step. This is the first time that this form of chiral 2]catenane has been observed. The enantiomers of the 2]catenane further self-assemble in the crystalline form, through secondary intermolecular PdX bonding, to form a racemic infinite supramolecular polymer of 2]catenanes.