Triethanolaminate iron perchlorate revisited: change of space group, chemical composition and oxidation states in [Fe₇(tea)₃(tea-H)₃](ClO₄)₂ (tea-H₃ is triethanolamine)

Abstract

The X-ray crystal structure of tris[N-(2-hydroxyethyl)-2,2'-iminodiethanolato]tris(2,2',2''-nitrilotriethanolato)tetrairon(II)triiron(III) bis(perchlorate), [Fe(CHNO)(CHNO)](ClO) or [Fe(tea)(tea-H)](ClO) (tea-H is triethanolamine), is known from the literature [Liu et al. (2008). Z. Anorg. Allg. Chem. 634, 778-783] as a heptanuclear coordination cluster. The space group was given as I23 and is reinvestigated in the present study. We find a new space-group symmetry of Pa-3 and could detect O-H hydrogens, which were missing in the original publication. Consequences on the Fe oxidation states are investigated with the bond-valence method, resulting in a mixed-valence core of four Fe and three Fe centres. Symmetry relationships between the two space groups and the average supergroup Ia-3 are discussed in detail.