Open AccessActivation of Dioxygen by a Mononuclear Nonheme Iron Complex: Sequential Peroxo, Oxo, and Hydroxo Intermediates
Author(s) -
Jesse B. Gordon,
Avery Vilbert,
Ida M. DiMucci,
Samantha N. MacMillan,
Kyle M. Lancaster,
Pierre MoënneLoccoz,
David Goldberg
Publication year - 2019
Publication title -
journal of the american chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.115
H-Index - 612
eISSN - 1520-5126
pISSN - 0002-7863
DOI - 10.1021/jacs.9b05274
Subject(s) - chemistry , electron paramagnetic resonance , reactivity (psychology) , bond cleavage , mössbauer spectroscopy , stoichiometry , photochemistry , raman spectroscopy , ferrous , absorption (acoustics) , x ray absorption spectroscopy , redox , medicinal chemistry , crystallography , stereochemistry , inorganic chemistry , absorption spectroscopy , catalysis , organic chemistry , nuclear magnetic resonance , medicine , physics , alternative medicine , pathology , quantum mechanics , acoustics , optics
The activation of dioxygen by Fe II (Me 3 TACN)(S 2 SiMe 2 ) ( 1 ) is reported. Reaction of 1 with O 2 at -135 °C in 2-MeTHF generates a thiolate-ligated (peroxo)diiron complex Fe III 2 (O 2 )(Me 3 TACN) 2 (S 2 SiMe 2 ) 2 ( 2 ) that was characterized by UV-vis (λ max = 300, 390, 530, 723 nm), Mössbauer (δ = 0.53, |Δ E Q | = 0.76 mm s -1 ), resonance Raman (RR) (ν(O-O) = 849 cm -1 ), and X-ray absorption (XAS) spectroscopies. Complex 2 is distinct from the outer-sphere oxidation product 1 ox (UV-vis (λ max = 435, 520, 600 nm), Mössbauer (δ = 0.45, |Δ E Q | = 3.6 mm s -1 ), and EPR ( S = 5/2, g = [6.38, 5.53, 1.99])), obtained by one-electron oxidation of 1 . Cleavage of the peroxo O-O bond can be initiated either photochemically or thermally to produce a new species assigned as an Fe IV (O) complex, Fe IV (O)(Me 3 TACN)(S 2 SiMe 2 ) ( 3 ), which was identified by UV-vis (λ max = 385, 460, 890 nm), Mössbauer (δ = 0.21, |Δ E Q | = 1.57 mm s -1 ), RR (ν(Fe IV ═O) = 735 cm -1 ), and X-ray absorption spectroscopies, as well as reactivity patterns. Reaction of 3 at low temperature with H atom donors gives a new species, Fe III (OH)(Me 3 TACN)(S 2 SiMe 2 ) ( 4 ). Complex 4 was independently synthesized from 1 by the stoichiometric addition of a one-electron oxidant and a hydroxide source. This work provides a rare example of dioxygen activation at a mononuclear nonheme iron(II) complex that produces both Fe III -O-O-Fe III and Fe IV (O) species in the same reaction with O 2 . It also demonstrates the feasibility of forming Fe/O 2 intermediates with strongly donating sulfur ligands while avoiding immediate sulfur oxidation.