title: Synthesis, characterization, and reactivity of iron trisamidoamine complexes that undergo both metal- and ligand-centered oxidative transformations.
abstract: Functional systems that combine redox-active metals and noninnocent ligands are no longer rare chemical oddities; they are instead emerging as significant components of catalytic and enzymatic reactions. The present work examines the synthetic and functional aspects of iron compounds ligated by a family of new trisamidoamine ligands of the type [(RNC6H4)3N]3- (L1). When R is the electron-rich 4-t-Bu-Ph moiety, the ligand can undergo oxidative rearrangement and store oxidizing equivalents under specific conditions. Starting ferrous complexes of the general formula [(L1)FeIIsolv]- (solv=CH3CN, dimethylformamide) can be easily oxidized (a) by dioxygen to afford the corresponding [(L1)FeIIIOH]- complexes, featuring several cases of terminal hydroxo units, and (b) by organochlorides (R-Cl) to provide [(L1)FeIIIsolv] congeners and coupled R-R products. Efforts to synthesize [(L1)FeIII-O-FeIII(L1)]2- by using [Cl3FeIII-O-FeIIICl3]2- indicate that intrinsic FeIIICl units can oxidatively rearrange the ligand to afford [(L1re)(Cl)FeII][Et4N]2, although the oxidizing equivalent is not retained. Compound [(L1re)(Cl)FeII][Et4N]2 can be further oxidized to [(L1re-2)(Cl)FeIII][Et4N] by CH2Cl2. Finally, oxidation of [(L1)FeIIIsolv] by FeCl3 affords [(L1reH)(Cl)FeII(micro-Cl)2FeII(Cl)(L1re-2H)], which features a similar ligand rearrangement that also gives rise to a diamagnetic, doubly oxidized moiety. These results underscore the complexity of chemical transformations available to systems in which both the metal and the ligand are redox-active entities.
authors.affiliation: Department of Chemistry, University of Missouri-Rolla, Rolla, Missouri 65409, USA.
authors.forename: Remle
authors.initials: R
authors.lastname: Celenligil-Cetin
authors.forename: Patrina
authors.initials: P
authors.lastname: Paraskevopoulou
authors.forename: Rupam
authors.initials: R
authors.lastname: Dinda
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Staples
authors.forename: Ekkehard
authors.initials: E
authors.lastname: Sinn
authors.forename: Nigam P
authors.initials: NP
authors.lastname: Rath
authors.forename: Pericles
authors.initials: P
authors.lastname: Stavropoulos
mesh_terms: D000588:Amines / Q000737:chemistry*; D004563:Electrochemistry; D007501:Iron / Q000737:chemistry*; D008024:Ligands; D008670:Metals / Q000737:chemistry*; D008958:Models, Molecular; D010084:Oxidation-Reduction
chemical_list: D000588:Amines; D008024:Ligands; D008670:Metals; D007501:Iron