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Science 14 January 2005:
Vol. 307. no. 5707, pp. 235 - 238
DOI: 10.1126/science.1106070
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Reports

A Stable Aminyl Radical Metal Complex

Torsten Büttner, Jens Geier, Gilles Frison, Jeffrey Harmer, Carlos Calle, Arthur Schweiger, Hartmut Schönberg, Hansjörg Grützmacher*

Metal-stabilized phenoxyl radicals appear to be important intermediates in a variety of enzymatic oxidations. We report that transition metal coordination also supports an aminyl radical, resulting in a stable crystalline complex: [Rh(I)(trop2N.)(bipy)]+OTf– (where trop is 5-H-dibenzo[a,d]cycloheptene-5-yl, bipy is 2,2'-bipyridyl, OTf– is trifluorosulfonate). It is accessible under mild conditions by one-electron oxidation of the amide complex [Rh(I)(trop2N)(bipy)], at a potential of –0.55 volt versus ferrocene/ferrocenium. Both electron paramagnetic resonance spectroscopy and density functional theory support 57% localization of the unpaired spin at N. In reactions with H-atom donors, the Rh-coordinated aminyl behaves as a nucleophilic radical.

Department of Chemistry and Applied Biosciences, ETH Hönggerberg, CH-8093 Zürich, Switzerland.

* To whom correspondence should be addressed. E-mail: gruetzmacher{at}inorg.chem.ethz.ch

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Structure of the Pyrroloquinoline Quinone Radical in Quinoprotein Ethanol Dehydrogenase.
C. W. M. Kay, B. Mennenga, H. Gorisch, and R. Bittl (2006)
J. Biol. Chem. 281, 1470-1476
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