A Nonheme Thiolate-Ligated Cobalt Superoxo Complex: Synthesis and Spectroscopic Characterization, Computational Studies, and Hydrogen Atom Abstraction Reactivity

The synthesis and characterization of a Co(II) dithiolato complex Co(Me TACN)(S SiMe ) (1) are reported. Reaction of 1 with O generates a rare thiolate-ligated cobalt-superoxo species Co(O )(Me TACN)(S SiMe ) (2) that was characterized spectroscopically and structurally by resonance Raman, EPR, and...

Full description

Saved in:
Bibliographic Details
Published in:Journal of the American Chemical Society Vol. 141; no. 8; p. 3641
Main Authors: Gordon, Jesse B, Vilbert, Avery C, Siegler, Maxime A, Lancaster, Kyle M, Moënne-Loccoz, Pierre, Goldberg, David P
Format: Journal Article
Language:English
Published: United States 27.02.2019
ISSN:1520-5126, 1520-5126
Online Access:Get more information
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The synthesis and characterization of a Co(II) dithiolato complex Co(Me TACN)(S SiMe ) (1) are reported. Reaction of 1 with O generates a rare thiolate-ligated cobalt-superoxo species Co(O )(Me TACN)(S SiMe ) (2) that was characterized spectroscopically and structurally by resonance Raman, EPR, and X-ray absorption spectroscopies as well as density functional theory. Metal-superoxo species are proposed to S-oxygenate metal-bound thiolate donors in nonheme thiol dioxygenases, but 2 does not lead to S-oxygenation of the intramolecular thiolate donors and does not react with exogenous sulfur donors. However, complex 2 is capable of oxidizing the O-H bonds of 2,2,6,6-tetramethylpiperidin-1-ol derivatives via H atom abstraction. Complementary proton-coupled electron-transfer reactivity is seen for 2 with separated proton/reductant pairs. The reactivity studies indicate that 2 can abstract H atoms from weak X-H bonds with bond dissociation free energy (BDFE) ≤ 70 kcal mol . DFT calculations predict that the putative Co(OOH) product has an O-H BDFE = 67 kcal mol , which matches the observed pattern of reactivity seen for 2. These data provide new information regarding the selectivity of S-oxygenation versus H atom abstraction in thiolate-ligated nonheme metalloenzymes that react with O .
Bibliography:ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 23
ISSN:1520-5126
1520-5126
DOI:10.1021/jacs.8b13134