chapter  8
18 Pages

Polynuclear Chelates with Tunable Aromaticity of Macrocyclic Equatorial Ligand

Abstract ................................................................................................. 126 8.1 Introduction .................................................................................. 126 8.2 Discussion .................................................................................... 127 Conclusions ........................................................................................... 139 Keywords .............................................................................................. 140 References ............................................................................................. 140

ABSTRACT

This chapter describes new polynuclear chelate ligand building blocks for promising catalysts for a variety of reactions. The chelates have planar, equatorial, macrocyclic, and aromatic ligand for two or more metal atoms in the polydentate cavity located in the center of the molecule. Structural analysis showed that in certain cases, these metals could actively participate in conjugation pathways of p-electrons of the overall macrocyclic structure. As a result, the aromatic macrocycle may have two or more stable states. Shifting between stable states of aromatic macrocyclic ligand would lead to simultaneous changes in the valency of the coordinated metals. Specifically, up to four electrons can be transferred from the equatorial ligand to the ligated metals in a single step. Since all these changes are purely electronic, no geometrical rearrangement in the chelate is required in shifting from the one stable state to another. This versatility could provide useful properties to such polynuclear chelates, including the facilitation of catalytic transformations due to their potential ability to activate inert substrates.