Macrocyclic squares, chiral

A new type of iodonium salts constitute the conformationally rigid, tetranu-clear macrocyclic ring systems dubbed molecular boxes. The relatively simpler tetraaryltetraiodonium salts were obtained from 4,4 -bis(diacetoxyiodo)bi-phenyl and 4,4 -bis(trimethylsilyl)biphenyl [119]. The iodonium salt derived from 4-(4 -lithiophenyl)pyridine was made using the method of /J-(dichloroio-do)chloroethylene and it was used for the construction of hybrid iodonium-platinum (or palladium) cationic tetranuclear macrocyclic squares including some in which the ligand of the metal was a chiral biphosphine [120,121]. 

Oenyuk, B., Whiteford, J.A. and Stang, P.J. (1996) Design and study of synthetic chiral nanoscopic assemblies. Preparation and characterization of optically active hybrid, iodonium-transition-metal and all-transition-metal macrocyclic molecular squares. J. Am. Chem. Soc., 118 (35), 8221-8230. 

When the reactive chiral building unit [M(/ -(+)-BINAP)(H20)][0Tf]2 with M = Pd (5.84) or M = Pt (5.85) was treated with the bridging ligand bis [4-(4 -pyridyl)phenyl) iodonium triflate (57), the related chiral hybrid supramolecular squares were formed (5.86-5.87) (hybrid = presence of iodonium and transition metal comers in the assembly). These hybrid molecular squares are optically active due to the chiral transition metal auxiliary (BINAP) in the assembly. Interestingly chiral induction was observed in these metallo-macrocycles since the preferred diastereomer in each preparation was formed in excess compared with the other isomers (Figure 5.34). ... 

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