Publication | Open Access
Tuning the Condensation Degree of {Fe<sup>III</sup><sub><i>n</i></sub>} Oxo Clusters via Ligand Metathesis, Temperature, and Solvents
26
Citations
28
References
2018
Year
Trinuclear μ<sub>3</sub>-oxo-centered iron(III) isobutyrate clusters readily react with polyalcohol organic ligands under one-pot synthesis conditions. Depending on the ligand, solvent, and temperature, a range of hexa-, dodeca-, and doicosanuclear iron(III) oxo-hydroxo condensation products, isolated as (mdeaH<sub>3</sub>)<sub>2</sub>[Fe<sub>6</sub>O(thme)<sub>4</sub>Cl<sub>6</sub>]·0.5(MeCN)·0.5(H<sub>2</sub>O) (1), [Fe<sub>12</sub>O<sub>4</sub>(OH)<sub>2</sub>(teda)<sub>4</sub>(N<sub>3</sub>)<sub>4</sub>(MeO)<sub>4</sub>]N<sub>3</sub>(NO<sub>3</sub>)<sub>0.5</sub>(MeO)<sub>0.5</sub>·2.5(H<sub>2</sub>O) (2), [Fe<sub>12</sub>O<sub>6</sub>(teda)<sub>4</sub>Cl<sub>8</sub>]·6(CHCl<sub>3</sub>) (3), [Fe<sub>22</sub>O<sub>16</sub>(OH)<sub>2</sub>(O<sub>2</sub>CCHMe<sub>2</sub>)<sub>18</sub>(bdea)<sub>6</sub>(EtO)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>]·2(EtOH)·5(MeCN)·6(H<sub>2</sub>O) (4), and [Fe<sub>22</sub>O<sub>14</sub>(OH)<sub>4</sub>(O<sub>2</sub>CCHMe<sub>2</sub>)<sub>18</sub>(mdea)<sub>6</sub>(EtO)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>](NO<sub>3</sub>)<sub>2</sub>·EtOH·H<sub>2</sub>O (5), where tedaH<sub>4</sub> = N, N, N', N'-tetrakis(2-hydroxyethyl)ethylenediamine; thmeH<sub>3</sub> = 1,1,1-tris(hydroxymethyl)ethane; mdeaH<sub>2</sub> = N-methyldiethanolamine; and bdeaH<sub>2</sub> = N-butyldiethanolamine. Complete carboxylate metathesis in the {Fe<sub>3</sub>} precursor complexes by thme<sup>3-</sup> or teda<sup>4-</sup> and the agglomeration of the formed species under solvothermal conditions afforded carboxylate-free {Fe<sub>6</sub>} product (1) in MeCN/CH<sub>2</sub>Cl<sub>2</sub> or {Fe<sub>12</sub>} complexes (2 and 3) in MeOH/EtOH and CHCl<sub>3</sub>/thf, respectively (thf = tetrahydrofuran). Single-crystal X-ray diffraction analyses revealed that 1 contains a [Fe<sub>6</sub>O(thme)<sub>4</sub>Cl<sub>6</sub>]<sup>2-</sup> cluster anion with a Lindqvist-type {Fe<sub>6</sub>(μ<sub>6</sub>-O)} core motif, charge-compensated by two protonated mdeaH<sub>3</sub><sup>+</sup> cations. 2 comprises a [Fe<sub>12</sub>O<sub>4</sub>(OH)<sub>2</sub>(teda)<sub>4</sub>(N<sub>3</sub>)<sub>4</sub>(MeO)<sub>4</sub>]<sup>2+</sup> cation with a {Fe<sub>12</sub>O<sub>4</sub>(OH)<sub>2</sub>}<sup>26+</sup> core, whereas 3 contains a charge-neutral [Fe<sub>12</sub>O<sub>6</sub>(teda)<sub>4</sub>(Cl)<sub>8</sub>] complex with an {Fe<sub>12</sub>O<sub>6</sub>}<sup>24+</sup> core. Finally, employing flexible bdeaH<sub>2</sub> or mdeaH<sub>2</sub> ligands under soft reaction conditions afforded giant {Fe<sub>22</sub>} oxo-hydroxo complexes (4 and 5) with a central {Fe<sub>6</sub>} layer sandwiched between two outer {Fe<sub>8</sub>} groups. Magnetic studies of 1-5 revealed strong antiferromagnetic coupling between the Fe<sup>III</sup> spin centers in all clusters.
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