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. 2016 Feb 1;7(2):1594-1599.
doi: 10.1039/c5sc03006d. Epub 2015 Dec 8.

Bimetallic iron-iron and iron-zinc complexes of the redox-active ONO pincer ligand

Janice L Wong  1 , Robert F Higgins  2 , Indrani Bhowmick  2 , David Xi Cao  1 , Géza Szigethy  1 , Joseph W Ziller  1 , Matthew P Shores  2 , Alan F Heyduk  1
Affiliations

Bimetallic iron-iron and iron-zinc complexes of the redox-active ONO pincer ligand

Janice L Wong et al. Chem Sci. .

Abstract

A new bimetallic platform comprising a six-coordinate Fe(ONO)2 unit bound to an (ONO)M (M = Fe, Zn) has been discovered ((ONOcat)H3 = bis(3,5-di-tert-butyl-2-phenol)amine). Reaction of Fe(ONO)2 with either (ONOcat)Fe(py)3 or with (ONOq)FeCl2 under reducing conditions led to the formation of the bimetallic complex Fe2(ONO)3, which includes unique five- and six-coordinate iron centers. Similarly, the reaction of Fe(ONO)2 with the new synthon (ONOsq˙)Zn(py)2 led to the formation of the heterobimetallic complex FeZn(ONO)3, with a six-coordinate iron center and a five-coordinate zinc center. Both bimetallic complexes were characterized by single-crystal X-ray diffraction studies, solid-state magnetic measurements, and multiple spectroscopic techniques. The magnetic data for FeZn(ONO)3 are consistent with a ground state S = 3/2 spin system, generated from a high-spin iron(ii) center that is antiferromagnetically coupled to a single (ONOsq˙)2- radical ligand. In the case of Fe2(ONO)3, the magnetic data revealed a ground state S = 7/2 spin system arising from the interactions of one high-spin iron(ii) center, one high-spin iron(iii) center, and two (ONOsq˙)2- radical ligands.

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Figures

Chart 1
Chart 1. Oxidation states of the ONO pincer ligand.
Fig. 1
Fig. 1. ORTEP diagrams of Fe2(ONO)3 (top) and FeZn(ONO)3 (bottom). Ellipsoids are drawn at 50% probability. Hydrogen atoms, methyl carbons of tert-butyl groups, and solvent molecules are omitted for clarity.
Scheme 1
Scheme 1. Synthesis of Fe2(ONO)3 by metathesis and redox pathways.
Scheme 2
Scheme 2. Synthesis of FeZn(ONO)3.
Fig. 2
Fig. 2. ORTEP diagram of one crystallographically unique (ONOsq˙)ZnII(py)2 molecule. Ellipsoids are drawn at 50% probability. Hydrogen atoms and pyridine and acetonitrile solvent molecules are omitted for clarity.
Fig. 3
Fig. 3. Temperature dependence of the dc magnetic susceptibility data for FeZn(ONO)3 (blue squares) and Fe2(ONO)3 (red circles) collected at an applied field of 1000 Oe; data have been corrected for TIP; the lines represent best fits to the models depicted in the inset schemes (julX).
Fig. 4
Fig. 4. Reduced field dependence of magnetization for Fe2(ONO)3; lines represent best fits of the data to an S = 7/2 ground state model, as determined by ANISOFIT.
See this image and copyright information in PMC

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