Sulfide oxidation by O2: Synthesis, structure and reactivity of novel sulfide-incorporated Fe(II) bis(imino)pyridine complexes

Widger, Leland R.; Siegler, Maxime A.; Goldberg, David

doi:10.1016/j.poly.2013.01.043

Cited by 10 publications

(6 citation statements)

References 79 publications

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“…Carboxylate-derived Fe–O distances have a similar range but depend on the binding mode of the carboxylate ligand (i.e., monodentate vs bidentate or terminal vs bridging). Additionally, in synthetic iron(II) complexes, Fe II –OH 2 distances can range from 2.04 to 2.16 Å, consistent with this assignment. − The Fe–O/N scatterer at 1.97 Å is assigned to the hydroxo bridge between the metal centers, as synthetic (μ-hydroxo)diferrous complexes have Fe II –μ-OH distances as short as 1.97 Å. − This assignment would agree with the single atom bridge observed in the crystal structure of WT R and give rise to a diiron(II) active site with an overall neutral charge. Mössbauer studies of WT R reveal a diiron(II) center with weak antiferromagnetic coupling ( J ∼ 12 cm –1 ) .…”

Section: Resultssupporting

confidence: 72%

A Carboxylate Shift Regulates Dioxygen Activation by the Diiron Nonheme β-Hydroxylase CmlA upon Binding of a Substrate-Loaded Nonribosomal Peptide Synthetase

Jasniewski

Knoot

Lipscomb³

et al. 2016

Biochemistry

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The first step in the nonribosomal peptide synthetase (NRPS)-based biosynthesis of chloramphenicol is the β-hydroxylation of the precursor L-para-aminophenylalanine (L-PAPA) catalyzed by the monooxygenase CmlA. The active site of CmlA contains a dinuclear iron cluster which is reduced to the diferrous state (WT R ) to initiate O 2 activation. However, rapid O 2 activation only occurs when WT R is bound to CmlP, the NRPS to which L-PAPA is covalently attached. Here the X-ray crystal structure of WT R is reported, which is very similar to that of the as-isolated diferric enzyme in which the irons are coordinately saturated. X-ray absorption spectroscopy is used to investigate the WT R cluster ligand structure as well as the structures of WT R in complex with a functional CmlP variant (CmlP AT ) with and without L-PAPA attached. It is found that formation of the active WT R -CmlP AT~L -PAPA complex converts at least one iron of the cluster from six-to five-coordinate by changing a bidentately bound amino acid carboxylate to monodentate on Fe1. The only bidentate carboxylate in the structure of WT R is E377. The crystal structure of the CmlA variant E377D shows only monodentate carboxylate coordination. Reduced E377D reacts rapidly with O 2 in the presence or absence of CmlP AT~L -PAPA, showing loss of regulation. However this variant fails to catalyze hydroxylation, suggesting that E377 has the dual role of coupling regulation of O 2 reactivity with juxtaposition of the substrate and the reactive oxygen species. The carboxylate shift in response to substrate binding represents a novel regulatory strategy for oxygen activation in diiron oxygenases. Graphical abstract * Corresponding Authors

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Section: Resultssupporting

confidence: 72%

A Carboxylate Shift Regulates Dioxygen Activation by the Diiron Nonheme β-Hydroxylase CmlA upon Binding of a Substrate-Loaded Nonribosomal Peptide Synthetase

Jasniewski

Knoot

Lipscomb³

et al. 2016

Biochemistry

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“…33,34 It must be stressed that the formation of the Schiff base is reversible, which imposes certain constraints on the synthesis. 35 2,6-Dimethylpyridine was also used as a starting material to synthesize dibenzoylpyridine, which was subsequently condensed with the aniline derivative to yield the diiminopyridine incorporating the phenyl rings attached to the imine carbon atoms (see Figure 4a). 21 Alternatively, dibenzoylpyridine was also obtained in a Friedel−Crafts acylation of benzene with 2,6dicarbonylpyridine dichloride.…”

Section: Distinct Synthetic Methodsmentioning

confidence: 99%

Progression of Diiminopyridines: From Single Application to Catalytic Versatility

2015

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Diiminopyridyl metal complexes, first characterized several decades ago, found practical application in 1998 when they were used as precatalysts in coordinative ethylene polymerization. This discovery contributed to the so-called postmetallocene revolution and triggered the large-scale experimental and theoretical research aimed at understanding diversified diiminopyridine chemistry. The results of this quest, some of which were intriguing and difficult to anticipate, are discussed and summarized in the current Review.

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“…[165] Methylation of the thiolate moiety to the methyl sulfide led to the formation of sulfoxide ands ulfone in lieu of sulfonic acid. [166] Substitution of triflate counter anion with different pyridines impacted the reactivity only modestly. [165] Later,i n2 011, [167] the authors demonstrated that the oxidation does not require the thiolate to be covalently anchored on the ligand.…”

Section: Other Imine-based Iron Complexesmentioning

confidence: 99%

Non‐Heme Imine‐Based Iron Complexes as Catalysts for Oxidative Processes

2016

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Non-heme iron complexes are emerging as powerful and versatile catalysts in several oxidative transformations. Them ost investigated iron complex structures are based on aminopyridine ligands,b ut an umber of imine-based ligands have been also tested. In this review ac ollection of recent results obtained in oxidation catalysisw ith non-heme iminebased iron complexes is presented. Theirc atalytic performances in C À H, C=Ca nd À S À oxidation are spread over aw ide range of efficiency,g oing from very low to quite high.S uch performances are discussed, whenever possible,i nl ight of the operating reactionm echanismsa nd of catalyst stability.I n order to facilitate the discussion,a ni nitial survey of the most useful mechanistic tools widelya pplied to distinguish am etal-based oxidation from ar adicalchain process is also reported. Imine-basedc atalysts are divided into twoc lasses:( i) salen-Fec omplexes, and (ii)i mine-Fe complexes.I ns ome cases clues for free-radical oxidation mechanisms have been reported whilei no ther casese vidence for metal-based mechanisms has been collected. Thep referredm echanisticp athway is shown to be af unction of catalyst structure and features

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Sulfide oxidation by O2: Synthesis, structure and reactivity of novel sulfide-incorporated Fe(II) bis(imino)pyridine complexes

Cited by 10 publications

References 79 publications

A Carboxylate Shift Regulates Dioxygen Activation by the Diiron Nonheme β-Hydroxylase CmlA upon Binding of a Substrate-Loaded Nonribosomal Peptide Synthetase

A Carboxylate Shift Regulates Dioxygen Activation by the Diiron Nonheme β-Hydroxylase CmlA upon Binding of a Substrate-Loaded Nonribosomal Peptide Synthetase

Progression of Diiminopyridines: From Single Application to Catalytic Versatility

Non‐Heme Imine‐Based Iron Complexes as Catalysts for Oxidative Processes

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