Homo‐ and Heterodinuclear Iron Clathrochelate Complexes with Functional Groups in the Ligand Periphery

Abstract

Dinuclear iron clathrochelate complexes were prepared by metal‐templated condensation reactions of 4‐pyridylboronic acid and phenol dioximes in the presence of FeIII and/or FeII salts. The complexes are accessible in two distinct redox states, featuring either two FeII centers or a mixed‐valence FeII/FeIII state. It is possible to reversibly switch between the two forms by chemical oxidation/reduction or electrochemically. A heterometallic ZnII/FeIII clathrochelate was obtained by using a mixture of zinc and iron salts. All complexes feature terminal pyridyl groups, which makes them interesting building blocks for metallosupramolecular chemistry. Metal ion exchange reactions indicate that the iron clathrochelate complexes are thermodynamically more stable than the analogous zinc and cobalt complexes. The high stability allowed to prepare a clathrochelate polymer by palladium‐catalyzed polycross‐coupling of a polybrominated clathrochelate complex with 1,4‐benzenediboronic acid. The polymer network displays permanent porosity with an apparent Brunauer–Emmett–Teller surface area of SABET = 510 m2 g–1. The polymer is thermally stable and not susceptible to hydrolytic degradation.