A Monomeric Nickel−Dioxygen Adduct Derived from a Nickel(I) Complex and O<sub>2</sub>

Fujita, Koyu; Schenker, Ralph; Gu, Weiwei; Brunold, Thomas C.; Cramer, Stephen P.; Riordan, Charles G.

doi:10.1021/ic049876n

Cited by 98 publications

(93 citation statements)

References 25 publications

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“…Samples of 3 prepared from 17 O 2 show minor EPR line broadening (estimated at ∼10 G), indicating that very little unpaired spin density resides on the O 2 ligand. 6 These observations suggest a spin coupled S ) 1 / 2 ground state 16 in agreement with literature precedents of transition metal superoxo species. 1 To further establish the geometric and electronic structures of 3, density functional theory (DFT) computational studies were performed on several models, considering both side-on and endon geometries as well as high-spin (HS, S ) 3 / 2 ) and low-spin (LS, S ) 1 / 2 ) ground states (SI for details).…”

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confidence: 88%

“…Significantly, 3 represents the first example of an end-on dioxygen complex in nickel coordination chemistry; side-on superoxo 6 and peroxo 20 adducts have been described previously. These diverse Ni/O 2 adducts provide the opportunity to evaluate inherent reactivity differences between the two coordination modes, which is a subject of considerable current interest.…”

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confidence: 89%

“…[PhTt Ad ]Ni(η 2 -O 2 ) displays analogous electrophilic propensity for PPh 3 , suggesting that side-on and end-on [NiO 2 ] + moieties engender similar reactivity characteristics. 6 However, the complex 3 does not react with less reactive substrates such as sulfides and olefins.…”

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confidence: 99%

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Identification of an “End-on” Nickel−Superoxo Adduct, [Ni(tmc)(O₂)]⁺

et al. 2006

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Identification of an “End-on” Nickel−Superoxo Adduct, [Ni(tmc)(O₂)]⁺

et al. 2006

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“…Crystallographic evidence for an analogous formulation has also recently been reported for a copper enzyme peptidylglycine ␣-hydroxylating monooxygenase (PHM) (8). Furthermore, synthetic copper(I) and nickel(I) complexes react with O 2 to give rise to copper and nickel superoxo species (9)(10)(11)(12)(13)(14)(15)(16) 2 was prepared by using the same procedure in the presence of 10 eq of D 2 O. All manipulations with complex 1 and solutions thereof were carried out under inert atmosphere by using a glovebox filled with nitrogen.…”

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“…Fig. 4 shows the resonance Raman spectra of samples generated by exposure of 1 to 16 A second resonance Raman spectrum was collected after warming up the sample to Ϫ70°C and maintaining it at this temperature for 15 min before freezing it for the Raman experiment. Under these conditions, the band at 1,310 cm Ϫ1 is still observed, but the bands at 831 and 483 cm Ϫ1 have vanished (Fig.…”

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Intermediates in the oxygenation of a nonheme diiron(II) complex, including the first evidence for a bound superoxo species

Shan

Que

2005

Proc. Natl. Acad. Sci. U.S.A.

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The reaction of [Fe2(-OH)2(6-Me3-TPA)2] 2؉ (1) [6-Me3-TPA, Tris(6-methyl-2-pyridylmethyl)amine] with O2 in CH2Cl2 at ؊80°C gives rise to two new intermediates, 2 and 3, before the formation of previously characterized [Fe2(O)(O2)(6-Me3-TPA)2] 2؉ (4) that allow the oxygenation reaction to be monitored one electron-transfer step at a time. Raman evidence assigns 2 and 3 as a diiron-superoxo species and a diiron-peroxo species, respectively. Intermediate 2 exhibits its (O-O) at 1,310 cm ؊1 with a ؊71-cm ؊1 18 O isotope shift. A doublet peak pattern for the 16 O 18 O isotopomer of 2 in mixedisotope Raman experiments strongly suggests that the superoxide ligand of 2 is bound end-on. This first example of a nonheme iron-superoxo intermediate exhibits the highest frequency (O-O) yet observed for a biomimetic metal-dioxygen adduct. The bound superoxide of 2, unlike the bound peroxide of 4, is readily reduced by 2,4-di-tert-butylphenol via a proton-coupled electron-transfer mechanism, emphasizing that metal-superoxo species may serve as oxidants in oxygen activation mechanisms of metalloenzymes. The discovery of intermediates 2 and 3 allows us to dissect the initial steps of dioxygen binding at a diiron center leading to its activation for substrate oxidation.nonheme diiron enzymes ͉ oxygen activation ͉ superoxo intermediate T he first step in the oxygen activation mechanisms of metalloenzymes is typically the binding of dioxygen, resulting in electron transfer from metal to O 2 to form a metal-superoxo species (1-5). This conversion is best exemplified by heme proteins and synthetic iron porphyrin complexes where there is strong crystallographic and spectroscopic evidence for an Fe III -( 1 -O 2•Ϫ ) formulation (6, 7). Crystallographic evidence for an analogous formulation has also recently been reported for a copper enzyme peptidylglycine ␣-hydroxylating monooxygenase (PHM) (8). Furthermore, synthetic copper(I) and nickel(I) complexes react with O 2 to give rise to copper and nickel superoxo species (9)(10)(11)(12)(13)(14)(15)(16) 2 was prepared by using the same procedure in the presence of 10 eq of D 2 O. All manipulations with complex 1 and solutions thereof were carried out under inert atmosphere by using a glovebox filled with nitrogen. Dichloromethane was distilled from CaH 2 under nitrogen. 2,4-di-tert-butylphenol (DTBP) was purchased from Aldrich and used as received. Saturated solutions of O 2 in CH 2 Cl 2 for the kinetic studies were prepared by bubbling the dried O 2 gas through the solvent for 10 min at room temperature. The concentration of O 2 in this saturated solution was accepted to be as reported in the literature (25) Sample Preparation. For UV-visible experiments, an anaerobic solution of 1⅐(OTf) 2 (3.3 mg) in dry CH 2 Cl 2 (3 ml) was introduced into a 1-cm-path-length cuvette and then cooled to 193 K in a Unisoku cryogenic cell holder attached to a HewlettPackard 8453A diode array spectrophotometer. O 2 gas was bubbled through the solution for 5 min, and the formation of 2 was complete within 1 h....

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