| Summary: | Reactions of Fe(II) with the tripodal chelating ligand 1,1,1-tris(2-pyridyl)ethoxymethane (py<sub>3</sub>C-OEt) and (NCE)<sup>−</sup> co-ligands (E = S, Se, BH<sub>3</sub>) give a series of mononuclear complexes formulated as [Fe(py<sub>3</sub>C-OEt)<sub>2</sub>][Fe(py<sub>3</sub>C-OEt)(NCE)<sub>3</sub>]<sub>2</sub>·2CH<sub>3</sub>CN, with E = S (<b>1</b>) and BH<sub>3</sub> (<b>2</b>). These compounds are the first Fe(II) spin cross-over (SCO) complexes based on the tripodal ligand tris(2-pyridyl)ethoxymethane and on the versatile co-ligands (NCS)<sup>−</sup> and (NCBH<sub>3</sub>)<sup>−</sup>. The crystal structure reveals discrete monomeric isomorph structures formed by a cationic [Fe(py<sub>3</sub>C-OEt)<sub>2</sub>]<sup>2+</sup> complex and by two equivalent anionic [Fe(py<sub>3</sub>C-OEt)(NCE)<sub>3</sub>]<sup>−</sup> complexes. In the cations the Fe(II) is facially coordinated by two py<sub>3</sub>C-OEt tripodal ligands whereas in the anion the three nitrogen atoms of the tripodal ligand are facially coordinated and the N-donor atoms of the three (NCE)<sup>−</sup> co-ligands occupy the remaining three positions to complete the distorted octahedral environment of the Fe(II) centre. The magnetic studies show the presence of gradual SCO for both complexes: A one-step transition around 205 K for <b>1</b> and a two-step transition for compound <b>2</b>, centered around 245 K and 380 K.
|
|---|