Synthesis, Characterization, and Reactivity of Iron Trisamidoamine Complexes That Undergo Both Metal- and Ligand-centered Oxidative Transformations
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 [(L1 re)(Cl)FeII][Et4N]2, although the oxidizing equivalent is not retained. Compound [(L1 re)(Cl)FeII][Et4N]2 can be further oxidized to [(L1 re-2)(Cl)FeIII][Et4N] by CH2Cl2. Finally, oxidation of [(L1)FeIIIsolv] by FeCl3 affords [(L1 reH)(Cl)FeII(í- Cl)2FeII(Cl)(L1 re-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.
R. Çelenligil-Çetin et al., "Synthesis, Characterization, and Reactivity of Iron Trisamidoamine Complexes That Undergo Both Metal- and Ligand-centered Oxidative Transformations," Inorganic Chemistry, American Chemical Society (ACS), Nov 2008.
The definitive version is available at http://dx.doi.org/10.1021/ic702154z
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National Science Foundation (U.S.)
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