Imposing control on self-assembly: rational design and synthesis of a mixed-metal, mixed-ligand coordination cage containing four types of component.

Retrosynthetic analysis of a [ML] coordination cage shows how it can be assembled rationally, in a stepwise manner, using a combination of kinetically inert and kinetically labile components. Combination of the components of -Ru(L), Cd(BF) and L in the necessary 4 : 12 : 12 stoichiometry afforded crystals of [RuCd(L)(L)]X (X = a mono-anion) in which the location of the two types of metal ion [Ru(ii) or Cd(ii)] at specific vertices in the metal-ion array, and the two types of bridging ligand (L and L) along specific edges, is completely controlled by the synthetic strategy. The incorporation of four different types of component at pre-determined positions in a coordination cage superstructure represents a substantial advance in imposing control on the self-assembly of complex metallosupramolecular entities.