Metallo-supramolecular squares

If 4,4 -bipyridine is mixed with (dppp)Pd(II) or (dppp)Pt(II) triflates (dppp = bis-(diphenylphosphine) propane), the two reactants spontaneously self-assembly [53] to the metallo-supramolecular square shown in Fig. 5.24, because the weakly coordinating counterions leave two coordination sites open at the metal complex. By virtue of the dppp ligand, the coordination angle of 90° is fixed. It is rather difficult to ionize these squares as intact but completely desolvated entities, but under the... 

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). ... 

Supramolecular systems based on Re(CO)3X (23) and other fragments, generally called metallo-cyclophanes or molecular squares, are recent. ... 

Figure 2.3 Solvent free supramolecular self assembly of a metallo-square.

---