Iron(III) complexes with 2‐pyridyl oxime ligands: Synthesis, structural and spectroscopic characterization, and magnetic studies

Reactions of Fe III sources with 2‐pyridyl oxime ligands, pyC(R)NOH (R=H, Me, Ph), afforded the trinuclear oxo‐centered complexes (NH 4 )[Fe 3 O(LH) 6 (H 2 O) 3 ](ClO 4 ) 8 ⋅MeOH⋅1.14H 2 O ( 1 ⋅ MeOH⋅1.14H 2 O) and [Fe 3 O{pyC(H)NO)(PhCO 2 ) 6 (H 2 O)]⋅MeCN ( 2 ⋅MeCN), the tetranuclear complex [Fe 4 (OH) 4 {pyC(Me)NO} 4 (H 2 O) 4 ] (ClO 4 ) 4 ⋅3Me 2 CO⋅H 2 O ( 3 ⋅3Me 2 CO⋅H 2 O), and the hexanuclear complexes [Fe 6 (OH) 6 {pyC(Me)NO} 6 (H 2 O) 6 ](ClO 4 ) 6 ⋅8Me 2 CO⋅2H 2 O ( 4 ⋅8Me 2 CO⋅2H 2 O), [Fe 6 (OH) 6 {pyC(Me)NO} 6 (MeCONH 2 ) 6 ](ClO 4 ) 6 ⋅2MeCN⋅H 2 O ( 5 ⋅2MeCN⋅H 2 O), [Fe 6 (OH) 6 {pyC(Ph)NO} 6 (H 2 O) 6 ](ClO 4 ) 6 ⋅4.4Me 2 CO ⋅1.6Et 2 O ( 6 ⋅4.4Me 2 CO ⋅1.6Et 2 O) and [Fe 6 (OH) 6 {pyC(Ph)NO} 6 (MeOH) 6 ](ClO 4 ) 5.5 (OH) 0.5 ⋅MeOH⋅0.5H 2 O ( 7 ⋅MeOH ⋅0.5H 2 O), where LH is the zwitterion anionic form of 2‐pyridinecarboxylic acid (picolinic acid). Complex 3 can be described as inverse 12‐metallacrown‐4, whereas 4–7 can be described as inverse 18‐metallacrowns‐6 and represent the first examples of iron(III) metallacyclic clusters with pyC(R)NOH (R=H, Me, Ph) ligands. Complexes 3 and 6 were characterized by Mössbauer spectroscopy and magnetic susceptibility measurements, while complex 2 was characterized by EPR spectroscopy.