title: Synthesis and characterization of N2S3X-Fe models of iron-containing nitrile hydratase.
abstract: A series of iron complexes based on the pentadentate ligand 4,7-bis(2'-methyl-2'-mercaptopropyl)-1-thia-4,7-diazacyclononane), (bmmp-TASN)(2)(-), have been synthesized and characterized as models of iron-containing nitrile hydratase (NHase). The chloro derivative [(bmmp-TASN)Fe(III)Cl].0.5EtOH (1) contains a labile chloride which facilitates synthesis of related complexes via substitution reactions. Complex 1 is high-spin, g = 4.28. Addition of NEt(4)CN with 1 in CH(2)Cl(2) results in the cyanide ligated complex [(bmmp-TASN)Fe(III)CN] x 0.5EtOH (2), which shows a single intense nu(CN) band at 2083 cm(-)(1) in the IR region. Complex 2 is low-spin, g(1) = 2.31, g(2) = 2.16, and g(3) = 1.96. Under basic conditions complex 1 affords a mu-oxo bridged dimeric Fe(III) complex [(bmmp-TASN)Fe(III)](2)O (3), which shows an intense band at 799 cm(-)(1). Complex 3 was recrystallized from CH(2)Cl(2)/hexane solution in the triclinic space group P1, with a = 10.5486(15) A, b = 13.0612(19) A, c = 8.1852(12) A, alpha = 96.923(2) degrees, beta = 112.729(2) degrees, gamma = 81.048(2) degrees, and Z = 1. Density functional theory (DFT) calculations of the previously communicated iron-nitrosyl complex [(bmmp-TASN)Fe(III)(NO)][BPh(4)] (4) (Inorg. Chem. 2002, 41, 1039-1041) reveal that the HOMO region is dominated by Fe-S bonding. Complexes 1-4 display irreversible or quasi-reversible reductions in the cyclic voltammograms. All of the iron complexes and the zinc derivative, (bmmp-TASN)Zn (5), display an irreversible oxidation. Complex 5 was crystallized in the monoclinic space group P2(1)/n with a = 9.5759(6) A, b = 20.9790(13) A, c = 10.7113(7) A, beta = 91.283(1) degrees, and Z = 4.
authors.affiliation: Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, USA. grapperhaus@louisville.edu
authors.forename: Craig A
authors.initials: CA
authors.lastname: Grapperhaus
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.forename: Apurba K
authors.initials: AK
authors.lastname: Patra
authors.forename: Selma
authors.initials: S
authors.lastname: Poturovic
authors.forename: Pawel M
authors.initials: PM
authors.lastname: Kozlowski
authors.forename: Marek Z
authors.initials: MZ
authors.lastname: Zgierski
authors.forename: Mark S
authors.initials: MS
authors.lastname: Mashuta
mesh_terms: D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D006836:Hydro-Lyases / Q000737:chemistry*; D007202:Indicators and Reagents; D008024:Ligands; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D013055:Spectrophotometry, Infrared
chemical_list: D007202:Indicators and Reagents; D008024:Ligands; D006836:Hydro-Lyases; C048831:nitrile hydratase