A Structural Probe for Organogold(I) Rings and [2]Catenanes

The digold(I) diacetylides [4-RC₆H₉(4-C₆H₄OCH₂C⋮CAu)₂], which contain a cyclohexylidene hinge group 4-RC₆H₉ with R = H or t-Bu, react with diphosphine ligands Ph₂PZPPh₂ to give the corresponding macrocycles or [2]catenanes [{4-RC₆H₉(4-C₆H₄OCH₂C⋮CAu)₂(μ-Ph₂PZPPh₂)}_y] [Z = C⋮C, (CH₂)₂, (CH₂)₃, or (CH₂)₄; y = 1, 2, or 4]. When R = t-Bu, the bulky tert-butyl group locks the cyclohexane ring conformation and so provides a good NMR spectroscopic probe of the structure. The organogold(I) [2]catenane complexes are chiral when R = t-Bu, and the complex with Z = (CH₂)₄ gives an equilibrium in solution between ring, double-ring, and [2]catenane. When R = H and Z = (CH₂)₃, the variable-temperature NMR spectra give new insight into the fluxionality in the [2]catenane complex, and when R = H and Z = (CH₂)₄, it is shown that the complex exists in solution as the ring structure, although it crystallizes as a doubly braided [2]catenane.