Isolation and characterization of unusual multinuclear Schiff base complexes: rearrangements reactions and octanuclear cluster formation

Abstract

The isolation and full characterization of multinuclear Schiff base complexes is reported, and their relevance as precursors for octanuclear Zn₈ salen cluster complex formation is discussed. Starting from simple precursors, three tetranuclear Zn₄ complexes were accessed that incorporate typical half-salen units and comprise of bridging acetates. The use of alternative reaction conditions or a step-wise approach smoothly leads to Zn₈ cluster formation. In addition, the tetranuclear Zn₄ complexes themselves may also serve as precursors toward Zn₈ cluster formation when treated under appropriate reaction conditions. The influence of the solvent medium in the latter Zn₄ → Zn₈ conversion was separately studied and revealed the formation of unusual pyridine-ligated multinuclear structures with fully condensed salen coordination pockets, providing a possible prelude to octanuclear cluster formation.