Synthesis and Crystal Structures of μ‐Oxido‐ and μ‐Hydroxido‐Bridged Dinuclear Iron(III) Complexes with an N₂O Donor Ligand – A Theoretical Study on the Influence of Weak Forces on the Fe–O–Fe Bridging Angle

Abstract

The synthesis and crystal structures of three nonheme diiron(III) complexes with a tridentate N,N,O Schiff‐baseligand, 2‐({[2‐(dimethylamino)ethyl]imino}methyl)phenol (HL), are reported. Complexes [Fe2OL2(NCO)2] (1a) and [Fe2OL2(SAL)2]·H2O [SAL = o‐(CHO)C6H4O–] (1b) are unsupported μ‐oxido‐bridged dimers, and [Fe2(OH)L2(HCOO)2(Cl)] (2) is a μ‐hydroxido‐bridged dimer supported by a formato bridging ligand. All complexes have been characterized by X‐ray crystallography and spectroscopic analysis. Complex 1b has been reported previously; however, it has been reinvestigated to confirm the presence of a crucial water molecule in the solid state. Structural analyses show that in 1a the iron atoms are pentacoordinate with a bent Fe–O–Fe angle [142.7(2)°], whereas in 2 the metal centers are hexacoordinate with a normal Fe–OH–Fe bridging angle [137.9(2)°]. The Fe–O–Fe angles in complexes 1a and 1b differ significantly to those usually shown by (μ‐oxido)FeIII complexes. A theoretical study has been performed in order to rationalize this deviation. Moreover, the influence of the water molecule observed in the solid‐state structure of 1b on the Fe–O–Fe angle is also analyzed theoretically.

Synthesis and Crystal Structure of a μ-Oxido-Bridged Dinuclear Iron(III) Complex Derived From 3, 5-Dichlorosalicylaldehyde and 4-(2-Aminoethyl)morpholine

“…The complex is a m-oxido-bridged dinuclear iron(III) complex, with Fe¢ ¢ ¢Fe separation of 3.467 (2) are within the range found for other m-oxido-bridged dinuclear iron complexes. [21][22][23] In addition, the Fe-O-Fe bond angle of 150.8 (1) in the complex is also similar to those observed in similar complexes with octahedral coordination, [21][22][23] but much smaller than the m-oxido-bridged dinuclear iron complexes with square pyramidal coordination. [24][25][26] …”

An iron(ii) hydride complex of a ligand with two adjacent β-diketiminate binding sites and its reactivity

“…In 2011 Gosh and coworkers reported a related compound, containing one bridging hydroxo and one bridging formate ligand, but in contrast to 6 the iron centers have the oxidation state +III. 18 All in all, complexes displaying a Fe( μ -OH)( μ -HCOO)Fe motif are rather rare.…”

Dehydrocoelenterazine is the Organic Substance Constituting the Prosthetic Group of Pholasin

“…Other purely O‐donor‐coordinated Fe III compounds have coordination numbers of four, based, for example, on sterically demanding O t Bu ligands 38,39. Pentacoordinate Fe III compounds are highly exciting compounds, as they are the main players in crucial applications such as oxygen transport in blood (non‐heme),35,40 enzymes,37 and catalysts 29–33. Complexes with coordination number five can process two different geometries, either square pyramidal or trigonal bipyramidal.…”