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.