Metal and ligand control in di- and octa-nuclear cluster formation

Reaction of doubly negatively charged m-pyridinediyl spacered bis-bidentate ligands with iron(III) chloride in the presence of alkaline, alkaline eart h, and rare earth metal cations (Mn+) yielded {2}-iron cryptates {M subset of [Fe-2(L)(3)]}(n+). The mono-, di-, and tri-valent guest cations are endo hedrally encapsulated in the cavity of the bicyclic dinuclear host. In cont rast, the ligands reacted with Mn2+, Co2+, and Cd2+ (M-II) cations as penta dentate tritopic chelators to give octanuclear complexes [(M8O2)-O-II(L)(6) ]. Similarly, a topological equivalent pentadentate tritopic ligand L' in t he presence of Zn2+ cations afforded the octanuclear cluster [Zn8O2(L')(6)] . However its reaction with iron(III) chloride and alkaline, alkaline earth , and rare earth metal cations did not lead to products of type {M subset o f [Fe-2(L)(3)]}(n+).