A tailor-made ligand to mimic the active site of diiron enzymes: an air-oxidized high-valent Fe^IIIh.s.(μ-O)₂Fe^IVh.s. species

Abstract

The design and first application of a new dinucleating ligand system to mimic high-valent oxidation states of O(2)-dependent diiron enzymes is presented.

Preparation and structures of dinuclear complexes containing MII–OH centers

“…Success in preparing dinuclear complexes with M–OH n unit in the syn -configuration has been achieved using dinucleating ligands. 7 For instance, Llobet and Meyer have reported complexes containing Ru 2 -(H 3 O 2 ), 7a Zn 2 -(H 3 O 2 ) 7b,c and Ni-(H 3 O 2 ) 7d unit respectively, utilizing a pyrazolate bridging group that prevents the formation hydroxo or oxo bridges. In this report we describe the preparation of a new dinucleating ligand that supports the formation of [Co II –OH] 2 and [Mn II –OH] 2 complexes.…”

“…Using the structural concepts developed by Meyer, 8 we reasoned that ligands containing a (3,5-diaminomethylene)-pyrazolate unit would provide sufficient spacing between the metal ions (ca 3.5-4.5 Å) to allow the binding of two terminal hydroxo ligands. In addition, our ligands include H-bond donors within the secondary coordination sphere to form intramolecular H-bonding networks with the M–OH units; 9,7d these types of noncovalent interactions have previously been exploited in the isolation of mononuclear M–OH analogues. 10 Two earlier versions of this design contained urea ([H 4 P R buam] 5- ) 11 and carboxyamidopyridyl ([H 3 bppap] 2- ) 12 groups (Fig.…”

Structural Diversity in Metal Complexes with a Dinucleating Ligand Containing Carboxyamidopyridyl Groups

“…To examine this possibility and evaluate the accessibility of the metal centers, we study the binding of water molecules to [M II 2 H 2 bppap] + complexes (Scheme 3). Treating either complex with 1 equiv of water produced the mono-hydroxide complexes, [{M II (OH)}M II H 3 bppap] + 12,14 . Our analytic and spectroscopic studies suggested that water addition caused protonation of the dinucleating ligand with concomitant binding of a hydroxide ion to one of the metal centers.…”

“…The Fourier transform IR spectrum supports this premise by having a single ν(O–H) peak at 3613 cm −1 and several broad ν(N–H) signals between 3400 and 3200 cm −1 , consistent with H-bonds involving the carboxyamido units. 14e …”

A Comprehensive Study on Triplesalen‐Based [MnIII6FeIII]3+ and [MnIII6FeII]2+ Complexes: Redox‐Induced Variation of Molecular Magnetic Properties

“…The ionic [Fe III (CN) 6 ] 3exhibits the corresponding wave at E 1/2 = -1.01 V in acetonitrile. [53] Magnetic Measurements +0.9 V for the redox potentials of the [M c (CN) 6 ] munit as a result of its encapsulation by two tricationic [(talen tBu 2 )Mn III 3 -(solv) n ] 3+ units yielding [Mn III 6 M c ] (6m)+ .…”