A New Hexanuclear Iron−Selenium Nitrosyl Cluster: Primary Exploration of the Preparation Methods, Structure, and Spectroscopic and Electrochemical Properties

NaNO2, and methanol. Complexes 1-3 were characterized by IR, UV-vis, 1 H NMR, electrochemistry, and singlecrystal X-raydiffractionanalysis.IRspectraofcomplexes1and2show thecharacteristicNOstretchingfrequenciesat 1694 and 1698 cm -1 , respectively, while the absorptions of complex 3 appear at 1799, 1744, and 1710 cm -1 . The UV-vis spectra of complexes 1-3 show different bands in the range of 259-562 nm, which are assigned to the transitions between orbitals delocalized over the Fe-S cluster, the ligand-to-metal charge transfer, π*NO-dFe, and the metal-to-ligand charge transfer, dFe-π*NO. Single-crystal X-ray structural analysis reveals that complex 1 crystallizes in the monoclinic P2(1)/n space group with two molecules per unit cell. Two parallel “chair-shaped” structures, consisting of three iron and three selenium atoms, are connected by Fe-Se bonds with an average distance of 2.341 A u ; each iron center is bonded to three selenium atoms and a nitrogen atom from the nitrosyl ligand withapseudotetrahedralcentergeometry.Cyclicvoltammogramsofcomplexes1and2displaytwocathodicandthree anodiccurrentpeakswithanunusuallystrongcathodicpeak.Furtherelectrochemicalinvestigationsdemonstratedthat the intensity of the unusually strong peak is a result of at least three processes. One is the quasi-reversible reduction, and the other two are from an irreversible electrochemical process, in which the compound goes through a typical electron transfer and chemical reaction mechanism. Compound 3 shows three quasi-reversible reductions.