Synthesis, Characterization, and Reactivity of a Series of Homo‐ and Hetero‐dinuclear Complexes based on an Asymmetric FloH Ligand System

Abstract

In a previous communication we reported the site‐directed generation of a heterodinuclear FeIIICuII complex (1) by using an asymmetric dinucleating ligand FloH. The iron(III) ion was introduced first on the preferential metal‐binding site of the ligand that led to the formation of the thermodynamically favored five‐membered chelate ring upon metal‐binding. Copper(II) was introduced in the next step. The stepwise metalation strategy reported previously has now been extended to synthesize a series of heterodinuclear FeIIIMII [M = Mn (2), Fe (3), Co (4), and Ni (5)] and FeIICuI (1a) as well as the homodinuclear CuICuI (6) complexes. The complexes were characterized by X‐ray crystallography (except for 1a and 6), and by a limited number of spectroscopic methods. Complex 1 with a labile solvent binding site at FeIII reacted with H2O2 to form a transient intermediate that showed reactivity typical of metal peroxide complexes. The metal centers in the complexes 2–5 are coordinatively saturated, and hence they showed no reactivity with H2O2. Complex 1a reacted with O2 via an intermolecular pathway to form a μ‐oxo bridged tetrameric complex 1b, which was structurally characterized. This is in contrast to the homodinuclear CuICuI and heme FeIICuI cores, which prefer an intramolecular pathway for O2 activation.

Mixed Valence (μ‐Phenoxido) FeIIFeIII and FeIIIFeIV Compounds: Electron and Proton Transfers

“… Unsymmetrical ligands HL[(Py) 2 )][(D) 2 ] with D=2‐hydroxybenzyl, [44] benzimidazolyl (R=H or Me), [45] or 2‐(2‐pyridyl)ethyl [46] …”

“…A few of them associate a bis‐picolylamine branch and another bis‐substituted one (Scheme 3). [44,46,47] …”