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

Abstract

Reaction of doubly negatively charged m-pyridinediyl spacered bis-bidentate ligands with iron(III) chloride in the presence of alkaline, alkaline earth, and rare earth metal cations (Mⁿ⁺) yielded {2}-iron cryptates {M⊂[Fe₂(L)₃]}ⁿ⁺. The mono-, di-, and tri-valent guest cations are endohedrally encapsulated in the cavity of the bicyclic dinuclear host. In contrast, the ligands reacted with Mn²⁺, Co²⁺, and Cd²⁺ (M^II) cations as pentadentate tritopic chelators to give octanuclear complexes [M^II₈O₂(L)₆]. Similarly, a topological equivalent pentadentate tritopic ligand L′ in the 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⊂[Fe₂(L)₃]}ⁿ⁺.