Synthesis and X-ray and spectral study of the compounds [Q(4)N](2)[Fe-2(S2O3)(2)(NO)(4)] (Q = Me, Et, n-Pr, n-Bu)

Iron nitrosyl complexes with general formula [Q(4)N](2)[Fe-2(S2O3)(2)(NO)(4 )] (Q = Me, Et, n-Pr, n-Bu) were synthesized by the exchange reaction of K- 2[Fe-2(S2O3)(2)(NO)(4)] with tetraalkylammonium bromides. The molecular and crystal structure of [(CH3)(4)N](2)[Fe-2(S2O3)(2)(NO)(4)] were studied by X-ray diffraction analysis. The iron atom in the four-membered cycle of the [2Fe-2S] anion is bound to another Fe atom and to two sulfur atoms and is coordinated by two nonequivalent NO groups, each bridging sulfur atom being bound to the SO3 group. The structurally equivalent iron atoms are in the state Fe1- (S = 1/2). The Mossbauer spectroscopy method shows that the comp lexes are diamagnetic due to the strong Fe-Fe bond. It is found that the SO 3 group provides higher stability of the thiosulfate anion than the anion i n Roussin's red salt [Fe2S2(NO)(4)](2-).