N,N-Dialkylcarbamato μ-oxo derivatives of iron(III)

A series of homoleptic N,N-dialkylcarbamates of iron(III), Fe(O2CNR2)3 [R=Et, iPr, cyclohexyl (cy), 1–3, respectively] have been prepared from anhydrous FeCl3 and the amine–CO2 system in toluene. The sparingly soluble N,N-dibenzyl complex of formula Fe(O2CNBz2)3 (4), was prepared by metathesis from the soluble N,N-di-iso-propyl derivative and NHBz2–CO2. When R=sBu, the R2NH–CO2 system operating on anhydrous FeCl3 in toluene gave the presumably tetranuclear chloro derivative Fe4(O2CNsBu2)11Cl (5). The nuclearity of this compound was inferred from the crystallographically established structure of the corresponding product of hydrolysis Fe4(μ3-O)(O2CNsBu2)9Cl (6), the latter consisting of a rhomb of four iron atoms with axes of 6.28 and 3.37 Å. The μ-oxo derivatives [Fe2O(O2CNEt2)4]n (7), and [Fe2O(O2CNcy2)4]n (8), have been obtained by controlled hydrolysis of the iron(III) homoleptic precursors. The high-nuclearity complexes [Fe2O(O2CNiPr2)4]n (9), and Fe10(μ3-O)3(μ4-O)3(O2CNEt2)17Cl (10), are reported being obtained by reacting [NH2Et2]2[Fe2OCl6] with amine–CO2. The decanuclear species 10 has been structurally characterised and found to contain a framework of three five-coordinated and seven six-coordinated iron atoms with three μ3-O and three μ4-O bridges, one terminal chlorine atom and seventeen bridging carbamato groups at the periphery of the molecule.