Homometallic Fe III 4 and Heterometallic {Fe III 4 Ln III 2 } (Ln = Dy, Tb) Complexes – Syntheses, Structures, and Magnetic Properties

The sequential reaction of the multisite coordination ligand 2‐methoxy‐6‐{[2‐(2‐hydroxyethylamino)ethylimino]methyl}phenol (LH 2 ) with Fe(ClO 4 ) 2 · 4H 2 O or a combination of Fe(ClO 4 ) 2 · 4H 2 O and Ln(NO 3 ) 3 · 5H 2 O [Dy III and Tb III ] in the presence of tetramethylammonium hydroxide and pivalic acid (pivH) under ambient conditions afforded a homometallic tetranuclear Fe III complex and heterometallic hexanuclear Fe III /Ln III complexes, namely, [Fe 4 (μ 3 ‐O) 2 (L) 4 ] · 3CH 3 CN · 2CH 3 OH ( 1 ), [Fe 4 Dy 2 (μ 3 ‐O) 2 (L) 2 (O 2 CCMe 3 ) 10 (MeOH)] · 2CH 3 CN ( 2 ), and [Fe 4 Tb 2 (μ 3 ‐O) 2 (L) 2 (O 2 CCMe 3 ) 10 (HO 2 CCMe 3 )] · H 2 O ( 3 ). Compounds 1 – 3 crystallize in the monoclinic system in space group P 2 1 / n ( Z = 4). The homometallic tetranuclear derivative 1 possesses three contiguous four‐membered Fe 2 O 2 rings in a ladderlike configuration. Each of the iron centers is hexacoordinate (2N, 4O) in a distorted octahedral geometry. On the other hand, 2 and 3 contain two symmetrically related Fe 2 Ln units that are joined to each other through oxygen atoms from the ethoxide side arms of the ligand L 2– ; the two lanthanide ions are located at the opposite ends of the hexanuclear core. In 2 and 3 , the lanthanide centers are eight‐ (distorted trigonal dodecahedron) and nine‐coordinate (distorted monocapped square antiprism), respectively, and the iron centers are hexacoordinate (distorted octahedral). Magnetic studies on 2 and 3 reveal the presence of weak antiferromagnetic coupling between the Fe III and Ln III ions.