Methanolysis and Phenolysis Routes to Fe6, Fe8, and Fe10 Complexes and Their Magnetic Properties:  A New Type of Fe8 Ferric Wheel

• Published in: Inorganic chemistry 2003-12, Vol.42 (24), p.7819-7829
• Main Authors: Cañada-Vilalta, Cristina, O'Brien, Ted A, Pink, Maren, Davidson, Ernest R, Christou, George
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic034706g

Alcoholysis of preformed tetranuclear and hexanuclear iron(III) clusters has been employed for the synthesis of four higher-nuclearity clusters. Treatment of [Fe4O2(O2CMe)7(bpy)2](ClO4) with phenol affords the hexanuclear cluster [Fe6O3(O2CMe)9(OPh)2(bpy)2](ClO4) (1). Reaction of [Fe6O2(OH)2(O2CR)10(hep)2] (R = But or Ph) with PhOH affords the new “ferric wheel” complexes [Fe8(OH)4(OPh)8(O2CR)12] [R = But (2) or Ph (3)]. Complexes 2 and 3 exhibit the same structure, which is an unprecedented type for Fe(III). In contrast, treatment of [Fe6O2(OH)2(O2CBut)10(hep)2] with MeOH leads to the formation of [Fe10(OMe)20(O2CBut)10] (4), which exhibits the more common type of ferric wheel seen in analogous complexes with other carboxylate groups. Solid-state variable-temperature magnetic susceptibility measurements indicate spin-singlet ground states for complexes 2 and 4. The recently developed semiempirical method ZILSH was used to estimate the pairwise exchange parameters (J AB) and the average spin couplings Ŝ A·Ŝ B between the Fe(III) centers, providing a clear depiction of the overall magnetic behavior of the molecules. All exchange interactions between adjacent Fe(III) atoms are antiferromagnetic.