| RESEARCH |
Direct O2 oxidations: New iron chemistry Iron(III) tetraamido macrocyclic ligand (TAML) complexes developed by Carnegie Mellon University chemistry professor Terry Collins increase the oxidizing power of hydrogen peroxide under mild conditions, making the catalysts useful as substitutes for environmentally unfriendly chlorine- and metal-based industrial oxidations. An international team led by Collins has now shown that TAML complexes can facilitate oxidations using molecular oxygen, a process the researchers knew was possible but for which they did not have definitive proof [J. Am. Chem. Soc., 127, 2505 (2005)]. Previously, only iron(II) complexes were known to react this way with O2. The team reacted solutions of a TAML complex (shown) with O2 at room temperature to generate an iron(IV) TAML dimer in which the iron atoms are linked by a bridging oxygen atom abstracted from O2. The dimer catalytically oxidizes alcohols to aldehydes and phosphines to phosphine oxides. The initial TAML complex is regenerated in the process. This new type of iron-oxygen chemistry is important in understanding biological oxidation processes and could further improve industrial oxidations, Collins tells C&EN. |
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