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 [(L 1)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)Fe II][Et4N]2, although the oxidizing equivalent is not retained. Compound [(L1 re)(Cl)Fe II][Et4N]2 can be further oxidized to [(L 1 re-2)(Cl)FeIII][Et4N] by CH 2Cl2. Finally, oxidation of [(L1)Fe IIIsolv] by FeCl3 affords [(L1 reH)(Cl)FeII(μ -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.




National Institutes of Health (U.S.)
National Science Foundation (U.S.)

Keywords and Phrases

Amine; Iron; Ligand; Metal; chemical Structure; Chemistry; Electrochemistry; Oxidation Reduction Reaction; Electrochemistry; Models, Molecular; Iron compounds

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Article - Journal

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© 2008 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Feb 2008