Oxygen Activation by Co(II) and a Redox Non-Innocent Ligand: Spectroscopic Characterization of a Radical–Co(II)–Superoxide Complex with Divergent Catalytic Reactivity

Amanda R. Corcos,† Omar Villanueva,‡,∇ Richard C. Walroth,§ Savita K. Sharma,‡ John Bacsa,‡ Kyle M. Lancaster,*,§ Cora E. MacBeth,*,‡ and John F. Berry*,†
 †Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave., Madison, Wisconsin 53706, United States ‡Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia 30322, United States

§Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States

J. Am. Chem. Soc., Article ASAP

DOI: 10.1021/jacs.5b12643

Publication Date (Web): January 22, 2016 

http://pubs.acs.org/doi/abs/10.1021/jacs.5b12643
http://pubs.acs.org/doi/pdf/10.1021/jacs.5b12643

ABSTRACT: Bimetallic (Et4N)2[Co2(L)2], (Et4N)2[1] (where (L)3− = (N(o-PhNC(O)iPr)2)3−) reacts with 2 equiv of O2 to form the monometallic species (Et4N)- [Co(L)O2], (Et4N)[3]. A crystallographically character- ized analog (Et4N)2[Co(L)CN], (Et4N)2[2], gives insight into the structure of [3]1−. Magnetic measurements indicate [2]2− to be an unusual high-spin CoII-cyano species (S = 3/2), while IR, EXAFS, and EPR spectros- copies indicate [3]1− to be an end-on superoxide complex with an S = 1/2 ground state. By X-ray spectroscopy and calculations, [3]1− features a high-spin CoII center; the net S = 1/2 spin state arises after the Co electrons couple to both the O2•− and the aminyl radical on redox non- innocent (L•)2−. Dianion [1]2− shows both nucleophilic and electrophilic catalytic reactivity upon activation of O2 due to the presence of both a high-energy, filled O2− π* orbital and an empty low-lying O2− π* orbital in [3]1−. 

Redox non-innocence enables  the catalytic reaction!!!