Mössbauer spectra of two extended series of basic iron(III) carboxylates [Fe3O(O2CR)6(H2O)6]A (A− = ClO4 −, NO3 −)

Abstract

Two series of basic iron(III) carboxylates [Fe3O(O2CR)6(H2O)3]A were prepared, with R = CCl3, CHBr2, CH2F, CH2Cl, C(OH)Ph2, H, Ph, (CH2)3Cl, Me, CHMe2, Et, CMe3. For the former series (1–12) A − = ClO $_{4}^{\,\,-}$ and for the latter (13–24) A − = NO $_{3}^{\,\,-}$ . Complexes with R = CF3 were inaccessible for either counteranion, with all synthetic attempts leading to the butterfly complex [Fe4O2(O2CCF3)8 (H2O)6]. Crystal structures of 1, 2, 5, 7, 9–12, 14, 16, 21 and 23 revealed the close structural similarity of the complexes. Mossbauer studies revealed very similar isomer shifts for all complexes in the region of 0.51–0.54 mm s − 1, and variable quadrupole splittings, ranging from 0.36 to 0.76 mm s − 1. Mossbauer studies of the complexes were carried out in frozen MeCN solutions in order to assess their stability in solution. All complexes proved to be stable in MeCN solutions, except complex 13 (R = CCl3, A − = NO $_{3}^{\,\,-})$ , which dissociated to a butterfly-type complex.