Ring-to-Cage Structural Conversion via Template Effect in a Gold(I) Metallosupramolecular System.

A unique example of a ring-to-cage structural conversion in a multinuclear gold(I) coordination system with d-penicillamine (d-H2 pen) is reported. The reaction of [Au2 Cl2 (dppe)] (dppe=1,2-bis(diphenylphosphino)ethane) with d-H2 pen in a 1:1 ratio gave [Au4 (dppe)2 (d-pen)2 ] ([1]), in which two [Au2 (dppe)]2+ units are linked by two d-pen S atoms in a cyclic form so as to have two bidentate-N,O coordination arms. The subsequent reaction of [1] with Cu(OTf)2 afforded [Au4 Cu(dppe)2 (d-pen)2 ]2+ ([2]2+ ), in which a CuII ion is chelated by the two coordination arms in [1] to form an AuI 4 CuII bicyclic metallocage. A similar reaction using Cu(NO3 )2 was accompanied by the ring expansion of [1] to [Au8 (dppe)4 (d-pen)4 ], leading to the production of [Au8 Cu2 (dppe)4 (d-pen)4 ]4+ ([3]4+ ). In [3]4+ , two CuII ions are each chelated by the two coordination arms to form an AuI 8 CuII 2 tricyclic metallocage, accommodating a nitrate ion. The use of Ni(NO3 )2 or Ni(OAc)2 instead of Cu(NO3 )2 commonly gave a tricyclic metallocage of [Au8 Ni2 (dppe)4 (d-pen)4 ]4+ ([4]4+ ), but a water molecule was accommodated inside the AuI 8 NiII 2 metallocage.