Heterometallic FeIII–CeIV complexes from the use of aliphatic aminoalcohol ligands

Abstract

Six novel heteronuclear FeIII/CeIV clusters with the ligands 3-amino-1-propanol (Hap) and 2-(hydroxymethyl)piperidine (Hhmpip) [FeIII4CeIV6O8(L)4((CH3)3CCO2)12(RCO2)4] (R=CH3, L=ap−, 1; R=ClCH2, L=ap−, 2; R=BrCH2, L=ap−, 3; R=C2H5, L=ap−, 4; R=CH3, L=hmpip−, 5) and ([Fe2Ce2Na2O2((CH3)3CCO2)8(N3)2(ap)2])∞ (6)∞ are reported. Compounds 1–5 were prepared from reactions of preformed trinuclear Fe3+ clusters with the ligands, in the presence of (NH4)2Ce(NO3)6 and RCO2M (R=CH3, M+=H+, 1; R=ClCH2, M+=Na+, 2; R=BrCH2, M+=Na+, 3; R=CH3CH2, M+=Na+, 4; R=CH3, M+=H+, 5) in 1:5:1:1 molar ratio in CH3CN. Complex (6·2CH3CN)∞ was prepared by a similar to the above described synthetic procedure that involved the use of NaN3 instead of RCO2M. To the best of our knowledge, compounds 1–6 are the initial examples of FeIII/CeIV species and rare examples of metal complexes with the ligands Hap and Hhmpip. The structures of 1–5 are composed of a distorted supertetrahedral [FeIII4CeIV6(μ4-O)4(μ3-O)4]20+ structural core, while (6·2CH3CN)∞ displays a [FeIII2CeIV2Na2(μ4-O)2]12+ core consisting of two tetrahedral units sharing one common edge. These two structural types are rather uncommon for mixed metal 3d/4f compounds although they are well-known for 3d metal cluster chemistry. Variable temperature dc magnetic susceptibility studies on powdered microcrystalline samples of 1 and (6·2CH3CN)∞ revealed the presence of weak antiferromagnetic interactions as expected on the basis of the large separations (>6Å) between the paramagnetic Fe3+ ions in both complexes.