LAUSR

Four crystalline nitrosyl-iron compounds of the {FeNO}(7)(S = 3/2) type with aminecarboxylato co-ligands were prepared from aqueous solutions of iron(II) sulfate, an equimolar amount of one of the co-ligands ethylenediamine-N,N'-diacetate (edda), nitrilotriacetate (nta), N,N'-bis(2-hydroxyethyl)ethylenediamine-N,N'-diacetate (bhedda) or ethylenediamine-N,N,N',N'-tetraacetate (edta) and gaseous nitric oxide. The hemihydrate [Fe(edda)(H2O)(NO)]0.5H(2)O (1.0.5H(2)O), a hydrated coordination polymer [{Fe(H2O)(4)}{Fe(NO)(nta)}(2)](n/n)2H(2)O = [Fe(H2O)(4)(2)(2)](n/n)2H(2)O with [Fe(NO)(nta)](-) (2) monoanions, the solvent-free complex [Fe(bhedda)(NO)] (3) and another coordination polymer [Fe(H2O)(2){Fe(NO)(Hedta)}(2)](n/n) = [Fe(H2O)(2)(4)(2)](n/n) with [Fe(Hedta)(NO)](-) (4) monoanions were investigated by crystallography and IR and UV/Vis spectroscopy. Structural peculiarities, such as a tilt of the NO ligand toward the O atom of a neighbouring carboxylato ligand, were analysed by DFT calculations. The stability of the aqueous solutions of the target compounds against inert-gas stripping was related to the low amount of the less stable aqua complex [Fe(H2O)(5)(NO)](2+) in the aqueous equilibria in addition to the intrinsic stability of the species.