Synthesis and crystal structures of mu-oxido- and mu-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

[eng] 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.