title: A new hexanuclear iron-selenium nitrosyl cluster: primary exploration of the preparation methods, structure, and spectroscopic and electrochemical properties.
abstract: A new hexanuclear iron-selenium nitrosyl cluster, [(n-Bu)(4)N](2)[Fe(6)Se(6)(NO)(6)] (1), and a hexanuclear iron-sulfur nitrosyl cluster, [(n-Bu)(4)N](2)[Fe(6)S(6)(NO)(6)] (2), were synthesized by the solvent-thermal reactions of [(n-Bu)(4)N][Fe(CO)(3)NO] with selenium or sulfur in methanol, while a tetranuclear iron-sulfur nitrosyl cluster, (Me(4)N)[Fe(4)S(3)(NO)(7)] (3), was also prepared by the solvent-thermal reaction of FeCl(2).4H(2)O with thiourea in the presence of (CH(3))(4)NCl, NaNO(2), and methanol. Complexes 1-3 were characterized by IR, UV-vis, (1)H NMR, electrochemistry, and single-crystal X-ray diffraction analysis. IR spectra of complexes 1 and 2 show the characteristic NO stretching frequencies at 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, pi*(NO)-d(Fe), and the metal-to-ligand charge transfer, d(Fe)-pi*(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; each iron center is bonded to three selenium atoms and a nitrogen atom from the nitrosyl ligand with a pseudotetrahedral center geometry. Cyclic voltammograms of complexes 1 and 2 display two cathodic and three anodic current peaks with an unusually strong cathodic peak. Further electrochemical investigations demonstrated that 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.
authors.affiliation: Department of Chemistry and Biochemistry, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, California 90840, USA. qwrm@yahoo.com.cn
authors.forename: Rongming
authors.initials: R
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Lijuan
authors.initials: L
authors.lastname: Li
mesh_terms: D018360:Crystallography, X-Ray; D004563:Electrochemistry; D007501:Iron / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D009603:Nitroso Compounds / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D012643:Selenium / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet
chemical_list: D009603:Nitroso Compounds; D009942:Organometallic Compounds; D007501:Iron; D012643:Selenium
references.citation: Inorg Chem. 1999 Jun 14;38(12):2947-2952
references.pmid: 11671043
references.citation: Science. 1992 Dec 18;258(5090):1862-5
references.pmid: 1361684
references.citation: Chem Commun (Camb). 2005 Jan 28;(4):477-9
references.pmid: 15654375
references.citation: Dalton Trans. 2009 Feb 7;(5):777-86
references.pmid: 19156270
references.citation: J Am Chem Soc. 1973 May 30;95(11):3523-34
references.pmid: 4708377
references.citation: Biochemistry. 2004 Mar 2;43(8):2314-22
references.pmid: 14979728
references.citation: Proteomics. 2006 Mar;6(5):1654-62
references.pmid: 16404723
references.citation: Proc Natl Acad Sci U S A. 1993 Nov 15;90(22):10769-72
references.pmid: 7504282
references.citation: J Am Chem Soc. 2004 Oct 27;126(42):13566-7
references.pmid: 15493884
references.citation: Proc Natl Acad Sci U S A. 1989 Dec;86(24):9846-50
references.pmid: 2557631
references.citation: Eur J Biochem. 1989 Dec 8;186(1-2):5-15
references.pmid: 2598939
references.citation: J Am Chem Soc. 2001 Nov 28;123(47):11664-72
references.pmid: 11716723
references.citation: Chem Rev. 2004 Feb;104(2):527-59
references.pmid: 14871134
references.citation: Inorg Chem. 2006 Oct 16;45(21):8462-4
references.pmid: 17029349
references.citation: Inorg Chem. 2003 Oct 20;42(21):6824-50
references.pmid: 14552635
references.citation: J Am Chem Soc. 2007 Feb 7;129(5):1151-9
references.pmid: 17263396
references.citation: Inorg Chem. 2003 Jul 28;42(15):4624-31
references.pmid: 12870953
references.citation: Nature. 1991 Jun 27;351(6329):714-8
references.pmid: 1712077
references.citation: Annu Rev Physiol. 1995;57:707-36
references.pmid: 7539994