Novel formation of a linear trinuclear ferric complex containing a .mu.-oxo bis(.mu.-acetato) and a .mu.-hydroxo bis(.mu.-acetato) bridge

Kitajima, Nobumasa; Amagai, Hironobu; Tamura, Nobuchika; Ito, Masami; Moro‐oka, Yoshihiko; Heerwegh, Kristel; Pénicaud, Alain; Mathur, Rajeev S.; Reed, Christopher A.; Boyd, Peter D. W.

doi:10.1021/ic00069a004

Cited by 37 publications

(36 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Instead, the spectral features resemble those reported by Kitajima et al for the linear trinuclear ferric complex [Fe 3+ 3 (O)(OH)(OAc) 4 ( iPr2 Tp) 2 ] ( 6 ), which is generated upon exposure of [Fe 2+ ( iPr2 Tp)(acac)] to O 2 in MeCN (as noted in the Introduction). 10 In support of this assignment, the EPR spectra of 5-acac and 5-acac PhF3 display an intense feature at g = 4.3 and a weaker peak at g = 8.83 (Supporting Information, Figure S3), identical to the spectrum reported for 6 . In addition, crystals of 5-acac PhF3 were obtained by allowing an aerobic solution of 1-acac PhF3 in MeCN to stand for several weeks.…”

Section: Results and Analysissupporting

confidence: 64%

“…29 Even more relevant to the current study is Kitajima’s report that [Fe 2+ (acac)( iPr2 Tp)] reacts with O 2 in toluene to give a green intermediate that is unstable even at −78 °C. 10 Although no spectroscopic characterization was performed, this species was presumed to be a µ-peroxo species. Second, we examined 4-acac with magnetic circular dichroism (MCD) spectroscopy, which is sensitive to the ground-state spin of chromophores.…”

Section: Results and Analysismentioning

confidence: 99%

“…In 1993, Kitajima and co-workers generated the complex [Fe 2+ ( iPr2 Tp)(acac)(MeCN)] (where R2 Tp = hydrotris-(pyrazol-1-yl)borate with R-groups at the 3- and 5-positions of the pyrazole rings). 10 Exposure to O 2 in MeCN at room temperature eventually produced crystals of the triiron(III) complex [Fe 3 (µ-O)(µ-OH)(µ-OAc) 4 ( iPr2 Tp) 2 ], where the bridging acetate ligands derive from the acac group of the ferrous precursor. Thus, this synthetic model exhibits Dke1-type reactivity, although generation of the acetate ligands may proceed via a different mechanism than the one employed by the enzyme.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Fe(II) Complexes That Mimic the Active Site Structure of Acetylacetone Dioxygenase: O₂ and NO Reactivity

et al. 2012

View full text Add to dashboard Cite

Acetylacetone dioxygenase (Dke1) is a bacterial enzyme that catalyzes the dioxygen-dependent degradation of β-dicarbonyl compounds. The Dke1 active site contains a nonheme monoiron(II) center facially ligated by three histidine residues (the 3His triad); coordination of the substrate in a bidentate manner provides a five-coordinate site for O2 binding. Recently, we published the synthesis and characterization of a series of ferrous β-diketonato complexes that faithfully mimic the enzyme-substrate intermediate of Dke1 (Park, H.; Baus, J.S.; Lindeman, S.V.; Fiedler, A.T. Inorg. Chem. 2011, 50, 11978–11989). The 3His triad was modeled with three different facially coordinating N3 supporting ligands, and substituted β-diketonates (acacX) with varying steric and electronic properties were employed. Here, we describe the reactivity of our Dke1 models toward O2 and its surrogate nitric oxide (NO), and report the synthesis of three new Fe(II) complexes featuring the anions of dialkyl malonates. Exposure of [Fe(Me2Tp)(acacX)] complexes (where R2Tp = hydrotris(pyrazol-1-yl)borate with R-groups at the 3- and 5-positions of the pyrazole rings) to O2 at −70 °C in toluene results in irreversible formation of green chromophores (λmax ~750 nm) that decay at temperatures above −60 °C. Spectroscopic and computational analyses suggest that these intermediates contain a diiron(III) unit bridged by a trans µ-1,2-peroxo ligand. The green chromophore is not observed with analogous complexes featuring Ph2Tp and PhTIP ligands (where PhTIP = tris(2-phenylimidazoly-4-yl)phosphine), since the steric bulk of the phenyl substituents prevents formation of dinuclear species. While these complexes are largely inert toward O2, Ph2Tp-based complexes with dialkyl malonate anions exhibit dioxygenase activity and thus serve as functional Dke1 models. The Fe/acacX complexes all react readily with NO to yield highspin (S = 3/2) {FeNO}7 adducts that were characterized with crystallographic, spectroscopic, and computational methods. Collectively, the results presented here enhance our understanding of the chemical factors involved in the oxidation of aliphatic substrates by nonheme iron dioxygenases.

show abstract

Section: Results and Analysissupporting

confidence: 64%

Section: Results and Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Fe(II) Complexes That Mimic the Active Site Structure of Acetylacetone Dioxygenase: O₂ and NO Reactivity

et al. 2012

View full text Add to dashboard Cite

show abstract

“…On exposure to air, this compound decomposes within one week to yield a trinuclear iron(III) complex containing m-oxobis(m-acetato) and m-hydroxobis(m-acetato) ligand constellations between the metal centers. [10] The bridging acetato ligands no doubt have their origin in the acetylacetonato ligands employed, and the question arises as to whether these acetato ligands were generated by a dioxygenating cleavage according to the enzyme reactivity. We therefore synthesized an analogue in which the isopropyl groups at the ligand are replaced by methyl groups to achieve a higher reactivity.…”

mentioning

confidence: 99%

A Trispyrazolylborato Iron Malonato Complex as a Functional Model for the Acetylacetone Dioxygenase

Siewert¹,

Limberg²

2008

Angew Chem Int Ed

View full text Add to dashboard Cite

show abstract

“…As discussed above for the enzyme, the cleavage rate increases with increasing potential of the substrate to act as a donor, and since obviously, unlike the [His 3 Fe] 2+ unit, the [TpFe] + moiety does not mediate the cleavage of acac, 33,32 most likely for electronic reasons, employment of a more electron rich substrate, like a malonate, promised reactivity. At the same time, malonates are related to β-ketoesters that are cleaved by Dke1, too.…”

Section: B Model Systemsmentioning

confidence: 99%

Utilizing the Trispyrazolyl Borate Ligand for the Mimicking of O₂-Activating Mononuclear Nonheme Iron Enzymes

Sallmann

Limberg

2015

Acc. Chem. Res.

View full text Add to dashboard Cite

Mononuclear, O2-activating nonheme iron enzymes are a fascinating class of metalloproteines, capable of realizing the most different reactions, ranging from C-H activation, via O atom transfer to C-C bond cleavage, in the course of O2 activation. They can lead us the way to achieve similar reactions with comparable efficiency and selectivity in chemical laboratories, which would be highly desirable aiming at accessing value-added products or to achieve degradation of unwanted compounds. Hence, these enyzmes motivate attempts to construct artificial low-molecular weight analogues, mimicking structural or functional characteristics. Such models can, for instance, provide insights about which of the features inherent to an active site are essential and guarantee the enzyme function, and from this kind of information the minimal requirements for a biomimetic or bioinspired complex that may be applied in catalysis can be derived. On the other hand, they can contribute to an understanding of the enzyme functioning. In order to create such replicates, it is important to faithfully mimic the surroundings of the iron centers in their active sites. Most of them feature two histidine residues and one carboxylate donor, while a few exhibit a deceptively simple (His)3Fe active site. For the simulation of these, the trispyrazolyl borate ligand (Tp) particularly offers itself, as the facial arrangement of three pyrazole donors is reminiscent of the three histidine-derived imidazole donors. The focus of this Account will be on bioinorganic/biomimetic research from our laboratory utilizing Tp ligands to develop molecular models for (i) two representatives of the (His)3Fe-enzyme family, namely, the cysteine dioxygenase (CDO) and acetyl acetone dioxygenase (Dke1), (ii) a related but less well-explored variant of the CDO-the 2-aminoethanethiol dioxygenase-as well as (iii) the 2-His-1-carboxylate representative 1-aminocyclopropane-1-carboxylic acid oxidase (ACCO). The CDO catalyzes the dioxygenation of cysteine with O2 to give cysteine sulfinic acid, which could be mimicked at TpFe units in a realistic manner. Furthermore, the successful dioxygenation of 2-aminoethanethiol at the same complex metal fragments lends further support to the hypothesis that the active sites of CDO and the one of 2-aminoethanethiol dioxygenase, whose structure is unknown, are quite similar. Dke1 is capable of cleaving diketones and ketoesters to give the corresponding carboxylic acids and α-keto aldehydes, and Tp-based models have achieved comparable C-C bond cleavage reactions. The ACCO develops ethylene from ACC in the course of oxidation, and recently this has been achieved the first time for a TpFe model, too.

show abstract

Novel formation of a linear trinuclear ferric complex containing a .mu.-oxo bis(.mu.-acetato) and a .mu.-hydroxo bis(.mu.-acetato) bridge

Cited by 37 publications

References 0 publications

Fe(II) Complexes That Mimic the Active Site Structure of Acetylacetone Dioxygenase: O₂ and NO Reactivity

Fe(II) Complexes That Mimic the Active Site Structure of Acetylacetone Dioxygenase: O₂ and NO Reactivity

A Trispyrazolylborato Iron Malonato Complex as a Functional Model for the Acetylacetone Dioxygenase

Utilizing the Trispyrazolyl Borate Ligand for the Mimicking of O₂-Activating Mononuclear Nonheme Iron Enzymes

Contact Info

Product

Resources

About

Novel formation of a linear trinuclear ferric complex containing a .mu.-oxo bis(.mu.-acetato) and a .mu.-hydroxo bis(.mu.-acetato) bridge

Cited by 37 publications

References 0 publications

Fe(II) Complexes That Mimic the Active Site Structure of Acetylacetone Dioxygenase: O2 and NO Reactivity

Fe(II) Complexes That Mimic the Active Site Structure of Acetylacetone Dioxygenase: O2 and NO Reactivity

A Trispyrazolylborato Iron Malonato Complex as a Functional Model for the Acetylacetone Dioxygenase

Utilizing the Trispyrazolyl Borate Ligand for the Mimicking of O2-Activating Mononuclear Nonheme Iron Enzymes

Contact Info

Product

Resources

About

Fe(II) Complexes That Mimic the Active Site Structure of Acetylacetone Dioxygenase: O₂ and NO Reactivity

Fe(II) Complexes That Mimic the Active Site Structure of Acetylacetone Dioxygenase: O₂ and NO Reactivity

Utilizing the Trispyrazolyl Borate Ligand for the Mimicking of O₂-Activating Mononuclear Nonheme Iron Enzymes