Gold(I) Macrocycles and Topologically Chiral [2]Catenanes

The design and synthesis of a new type of topologically chiral [2]catenane is reported. The
compounds are formed easily by self-assembly on reaction of the oligomeric digold(I) diacetylide precursor
complex [{4-BrC6H4CH(4-C6H4OCH2CCAu)2}n] with diphosphine ligands. Reactions with the diphosphines
PP = bis(diphenylphosphinophoshino)acetylene, trans-1,2-bis(diphenylphosphino)ethylene, bis(diphenylphosphino)ethane, and 1,1‘-bis(diphenylphosphino)ferrocene yield simple ring complexes [4-BrC6H4CH(4-C6H4OCH2CCAu)2(μ-PP)] as the only products, since the spacer groups in the diphosphines are not
long enough or are too bulky to allow catenane formation. Reaction with PP = bis(diphenylphosphino)propane or bis(diphenylphosphino)butane gave [2]catenane complexes [{4-BrC6H4CH(4-C6H4OCH2CCAu)2(μ-PP)}2], whose structures are confirmed crystallographically. The macrocyclic ring compounds have Cs
symmetry but, as a result of the presence of the unsymmetrical “hinge group” 4-BrC6H4CH, the [2]catenanes
have C2 symmetry and so are topologically chiral. In favorable cases, the formation of the [2]catenane can
be proved by NMR spectroscopy since catenane formation leads to nonequivalence of most ring atoms.
The formation of the [2]catenanes was successfully predicted based on the conformation of the precursor
bis(phenol), and it is argued that the methods used should be more generally applicable to the synthesis
of functionally substituted supermolecules of interest for application in molecular devices.