title: Oxygen Activation by Co(II) and a Redox Non-Innocent Ligand: Spectroscopic Characterization of a Radical-Co(II)-Superoxide Complex with Divergent Catalytic Reactivity.
abstract: Bimetallic (Et4N)2[Co2(L)2], (Et4N)2[1] (where (L)(3-) = (N(o-PhNC(O)(i)Pr)2)(3-)) reacts with 2 equiv of O2 to form the monometallic species (Et4N)[Co(L)O2], (Et4N)[3]. A crystallographically characterized 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 Co(II)-cyano species (S = 3/2), while IR, EXAFS, and EPR spectroscopies 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 Co(II) 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-).
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison , 1101 University Ave., Madison, Wisconsin 53706, United States.
authors.forename: Amanda R
authors.initials: AR
authors.lastname: Corcos
authors.affiliation: Department of Chemistry, Emory University , 1515 Dickey Drive, Atlanta, Georgia 30322, United States.
authors.forename: Omar
authors.initials: O
authors.lastname: Villanueva
authors.affiliation: Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Richard C
authors.initials: RC
authors.lastname: Walroth
authors.affiliation: Department of Chemistry, Emory University , 1515 Dickey Drive, Atlanta, Georgia 30322, United States.
authors.forename: Savita K
authors.initials: SK
authors.lastname: Sharma
authors.affiliation: Department of Chemistry, Emory University , 1515 Dickey Drive, Atlanta, Georgia 30322, United States.
authors.forename: John
authors.initials: J
authors.lastname: Bacsa
authors.affiliation: Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University , Ithaca, New York 14853, United States.
authors.forename: Kyle M
authors.initials: KM
authors.lastname: Lancaster
authors.affiliation: Department of Chemistry, Emory University , 1515 Dickey Drive, Atlanta, Georgia 30322, United States.
authors.forename: Cora E
authors.initials: CE
authors.lastname: MacBeth
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison , 1101 University Ave., Madison, Wisconsin 53706, United States.
authors.forename: John F
authors.initials: JF
authors.lastname: Berry
mesh_terms: D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D008024:Ligands; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D013481:Superoxides / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D008024:Ligands; D013481:Superoxides; D003035:Cobalt; D010100:Oxygen