Self-Assembly of Gold(I) Rings and Reversible Formation of Organometallic [2]Catenanes

The reaction of the digold(I) diacetylide [(AuCCCH2OC6H4)2CMe2] with diphosphane ligands can lead to formation of either macrocyclic ring complexes or [2]catenanes by self‐assembly. This gives an easy route to rare organometallic [2]catenanes, and the effect of the diphosphane ligand on the selectivity of self‐assembly is studied. With diphosphane ligands Ph2P(CH2)xPPh2, the simple ring complex [Au2{(CCCH2OC6H4)2CMe2}(Ph2P(CH2)xPPh2)] is formed selectively when x=2, but the [2]catenanes [Au2{(CCCH2OC6H4)2CMe2}(Ph2P(CH2)xPPh2)]2 are formed when x=4 or 5. When x=3, a mixture of the simple ring and [2]catenane is formed, along with the “double‐ring” complex, [Au4{(CCCH2OC6H4)2CMe2}2(Ph2P(CH2)3PPh2)2] and a “hexamer” [{Au2[(CCCH2OC6H4)2CMe2](Ph2P(CH2)3PPh2)}6] whose structure is not determined. A study of the equilibria between these complexes by solution NMR techniques gives insight into the energetics and mechanism of [2]catenane formation. When the oligomer [(AuCCCH2OC6H4)2CMe2] was treated with a mixture of two diphosphane ligands, or when two [2]catenane complexes [{Au2[(CCCH2OC6H4)2CMe2](diphosphane)}2] were allowed to equilibrate, only the symmetrical [2]catenanes were formed. The diphosphanes Ph2PCCPPh2, trans‐[Ph2PCH=CHPPh2] and (Ph2PC5H4)2Fe give the corresponding ring complexes [Au2{(CCCH2OC6H4)2CMe2}(diphosphane)], and the chiral, unsymmetrical diacetylide [Au2{(CCCH2OC6H4C(Me)(CH2CMe2)C6H3OCH2CC)] gives macrocyclic ring complexes with all diphosphane ligands Ph2P(CH2)xPPh2 (x=2–5). The first family of organometallic [2]catenanes is based on digold(I) diacetylide diphosphane complexes (e.g. catenane 1). In some cases, self‐assembly of the products is selective but in others there is an equilibrium between simple rings and [2]catenanes.