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Theodor Agapie - One of the best experts on this subject based on the ideXlab platform.
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A trans-Hyponitrite Intermediate in the Reductive Coupling and Deoxygenation of Nitric Oxide by a Tricopper–Lewis Acid Complex
Journal of the American Chemical Society, 2016Co-Authors: Davide Lionetti, Graham De Ruiter, Theodor AgapieAbstract:The reduction of nitric oxide (NO) to nitrous oxide (N2O) is a process relevant to biological chemistry as well as to the abatement of certain environmental pollutants. One of the proposed key intermediates in NO reduction is Hyponitrite (N2O22–), the product of reductive coupling of two NO molecules. We report the reductive coupling of NO by an yttrium–tricopper complex generating a trans-Hyponitrite moiety supported by two μ-O-bimetallic (Y,Cu) cores, a previously unreported coordination mode. Reaction of the Hyponitrite species with Bronsted acids leads to the generation of N2O, demonstrating the viability of the Hyponitrite complex as an intermediate in NO reduction to N2O. The additional reducing equivalents stored in each tricopper unit are employed in a subsequent step for N2O reduction to N2, for an overall (partial) conversion of NO to N2. The combination of Lewis acid and multiple redox active metals facilitates this four electron conversion via an isolable Hyponitrite intermediate.
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a trans Hyponitrite intermediate in the reductive coupling and deoxygenation of nitric oxide by a tricopper lewis acid complex
Journal of the American Chemical Society, 2016Co-Authors: Davide Lionetti, Graham De Ruiter, Theodor AgapieAbstract:The reduction of nitric oxide (NO) to nitrous oxide (N2O) is a process relevant to biological chemistry as well as to the abatement of certain environmental pollutants. One of the proposed key intermediates in NO reduction is Hyponitrite (N2O22–), the product of reductive coupling of two NO molecules. We report the reductive coupling of NO by an yttrium–tricopper complex generating a trans-Hyponitrite moiety supported by two μ-O-bimetallic (Y,Cu) cores, a previously unreported coordination mode. Reaction of the Hyponitrite species with Bronsted acids leads to the generation of N2O, demonstrating the viability of the Hyponitrite complex as an intermediate in NO reduction to N2O. The additional reducing equivalents stored in each tricopper unit are employed in a subsequent step for N2O reduction to N2, for an overall (partial) conversion of NO to N2. The combination of Lewis acid and multiple redox active metals facilitates this four electron conversion via an isolable Hyponitrite intermediate.
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A trans-Hyponitrite Intermediate in the Reductive Coupling and Deoxygenation of Nitric Oxide by a Tricopper–Lewis Acid Complex
2016Co-Authors: Davide Lionetti, Graham De Ruiter, Theodor AgapieAbstract:The reduction of nitric oxide (NO) to nitrous oxide (N2O) is a process relevant to biological chemistry as well as to the abatement of certain environmental pollutants. One of the proposed key intermediates in NO reduction is Hyponitrite (N2O22–), the product of reductive coupling of two NO molecules. We report the reductive coupling of NO by an yttrium–tricopper complex generating a trans-Hyponitrite moiety supported by two μ-O-bimetallic (Y,Cu) cores, a previously unreported coordination mode. Reaction of the Hyponitrite species with Brønsted acids leads to the generation of N2O, demonstrating the viability of the Hyponitrite complex as an intermediate in NO reduction to N2O. The additional reducing equivalents stored in each tricopper unit are employed in a subsequent step for N2O reduction to N2, for an overall (partial) conversion of NO to N2. The combination of Lewis acid and multiple redox active metals facilitates this four electron conversion via an isolable Hyponitrite intermediate
Davide Lionetti - One of the best experts on this subject based on the ideXlab platform.
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A trans-Hyponitrite Intermediate in the Reductive Coupling and Deoxygenation of Nitric Oxide by a Tricopper–Lewis Acid Complex
Journal of the American Chemical Society, 2016Co-Authors: Davide Lionetti, Graham De Ruiter, Theodor AgapieAbstract:The reduction of nitric oxide (NO) to nitrous oxide (N2O) is a process relevant to biological chemistry as well as to the abatement of certain environmental pollutants. One of the proposed key intermediates in NO reduction is Hyponitrite (N2O22–), the product of reductive coupling of two NO molecules. We report the reductive coupling of NO by an yttrium–tricopper complex generating a trans-Hyponitrite moiety supported by two μ-O-bimetallic (Y,Cu) cores, a previously unreported coordination mode. Reaction of the Hyponitrite species with Bronsted acids leads to the generation of N2O, demonstrating the viability of the Hyponitrite complex as an intermediate in NO reduction to N2O. The additional reducing equivalents stored in each tricopper unit are employed in a subsequent step for N2O reduction to N2, for an overall (partial) conversion of NO to N2. The combination of Lewis acid and multiple redox active metals facilitates this four electron conversion via an isolable Hyponitrite intermediate.
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a trans Hyponitrite intermediate in the reductive coupling and deoxygenation of nitric oxide by a tricopper lewis acid complex
Journal of the American Chemical Society, 2016Co-Authors: Davide Lionetti, Graham De Ruiter, Theodor AgapieAbstract:The reduction of nitric oxide (NO) to nitrous oxide (N2O) is a process relevant to biological chemistry as well as to the abatement of certain environmental pollutants. One of the proposed key intermediates in NO reduction is Hyponitrite (N2O22–), the product of reductive coupling of two NO molecules. We report the reductive coupling of NO by an yttrium–tricopper complex generating a trans-Hyponitrite moiety supported by two μ-O-bimetallic (Y,Cu) cores, a previously unreported coordination mode. Reaction of the Hyponitrite species with Bronsted acids leads to the generation of N2O, demonstrating the viability of the Hyponitrite complex as an intermediate in NO reduction to N2O. The additional reducing equivalents stored in each tricopper unit are employed in a subsequent step for N2O reduction to N2, for an overall (partial) conversion of NO to N2. The combination of Lewis acid and multiple redox active metals facilitates this four electron conversion via an isolable Hyponitrite intermediate.
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A trans-Hyponitrite Intermediate in the Reductive Coupling and Deoxygenation of Nitric Oxide by a Tricopper–Lewis Acid Complex
2016Co-Authors: Davide Lionetti, Graham De Ruiter, Theodor AgapieAbstract:The reduction of nitric oxide (NO) to nitrous oxide (N2O) is a process relevant to biological chemistry as well as to the abatement of certain environmental pollutants. One of the proposed key intermediates in NO reduction is Hyponitrite (N2O22–), the product of reductive coupling of two NO molecules. We report the reductive coupling of NO by an yttrium–tricopper complex generating a trans-Hyponitrite moiety supported by two μ-O-bimetallic (Y,Cu) cores, a previously unreported coordination mode. Reaction of the Hyponitrite species with Brønsted acids leads to the generation of N2O, demonstrating the viability of the Hyponitrite complex as an intermediate in NO reduction to N2O. The additional reducing equivalents stored in each tricopper unit are employed in a subsequent step for N2O reduction to N2, for an overall (partial) conversion of NO to N2. The combination of Lewis acid and multiple redox active metals facilitates this four electron conversion via an isolable Hyponitrite intermediate
George B. Richter-addo - One of the best experts on this subject based on the ideXlab platform.
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Not Limited to Iron: A Cobalt Heme–NO Model Facilitates N–N Coupling with External NO in the Presence of a Lewis Acid to Generate N2O
Angewandte Chemie (International ed. in English), 2019Co-Authors: Erwin G. Abucayon, Douglas R. Powell, Rahul L. Khade, Yong Zhang, George B. Richter-addoAbstract:Some bacterial heme proteins catalyze the coupling of two NO molecules to generate N2 O. We previously reported that a heme Fe-NO model engages in this N-N bond-forming reaction with NO. We now demonstrate that (OEP)CoII (NO) similarly reacts with 1 equiv of NO in the presence of the Lewis acids BX3 (X=F, C6 F5 ) to generate N2 O. DFT calculations support retention of the CoII oxidation state for the experimentally observed adduct (OEP)CoII (NO⋅BF3 ), the presumed Hyponitrite intermediate (P.+ )CoII (ONNO⋅BF3 ), and the porphyrin π-radical cation by-product of this reaction, and that the π-radical cation formation likely occurs at the Hyponitrite stage. In contrast, the Fe analogue undergoes a ferrous-to-ferric oxidation state conversion during this reaction. Our work shows that cobalt hemes are chemically competent to engage in the NO-to-N2 O conversion reaction.
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A bridged di-iron porphyrin Hyponitrite complex as a model for biological N2O production from Hyponitrite.
Nitric oxide : biology and chemistry, 2015Co-Authors: Erwin G. Abucayon, Douglas R. Powell, George B. Richter-addoAbstract:Heme-Hyponitrites are intermediates that form at the bimetallic active sites of bacterial nitric oxide reductases. To probe a possible effect of the Fe-Fe distance on Hyponitrite stability, we prepared a bridged bis-porphyrin Fe-Hyponitrite compound, namely [(OEP-CH2)Fe]2(μ2,η(1),η(1)-ONNO). Its υNO of 992 cm(-1) (υ15NO of 976 cm(-1)) is close to the υNO of 983 cm(-1) reported previously by us for the crystallographically characterized [(OEP)Fe]2(μ2,η(1),η(1)-ONNO) compound. The bridged bis-porphyrin Fe-Hyponitrite complex is unstable with respect to N2O production, supporting the role of the bis-Fe porphyrin system in Hyponitrite conversion to N2O. The preparation and crystallographic determination of the bridging sulfato derivative is also reported.
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Characterization of the Bridged Hyponitrite Complex {[Fe(OEP)]2(μ-N2O2)}: Reactivity of Hyponitrite Complexes and Biological Relevance
Inorganic chemistry, 2014Co-Authors: Timothy C. Berto, George B. Richter-addo, Ryeon Lee, Anne J. Mcneil, E. Ercan Alp, Jiyong Zhao, Nicolai LehnertAbstract:The detoxification of nitric oxide (NO) by bacterial NO reductase (NorBC) represents a paradigm of how NO can be detoxified anaerobically in cells. In order to elucidate the mechanism of this enzyme, model complexes provide a convenient means to assess potential reaction intermediates. In particular, there have been many proposed mechanisms that invoke the formation of a Hyponitrite bridge between the heme b3 and nonheme iron (FeB) centers within the NorBC active site. However, the reactivity of bridged iron Hyponitrite complexes has not been investigated much in the literature. The model complex {[Fe(OEP)]2(μ-N2O2)} offers a unique opportunity to study the electronic structure and reactivity of such a Hyponitrite-bridged complex. Here we report the detailed characterization of {[Fe(OEP)]2(μ-N2O2)} using a combination of IR, nuclear resonance vibrational spectroscopy, electron paramagnetic resonance, and magnetic circular dichroism spectroscopy along with SQUID magnetometry. These results show that the gr...
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Characterization of the Bridged Hyponitrite Complex {[Fe(OEP)]2(μ‑N2O2)}: Reactivity of Hyponitrite Complexes and Biological Relevance
2014Co-Authors: Timothy C. Berto, George B. Richter-addo, Anne J. Mcneil, E. Ercan Alp, Jiyong Zhao, Se Ryeon Lee, Nicolai LehnertAbstract:The detoxification of nitric oxide (NO) by bacterial NO reductase (NorBC) represents a paradigm of how NO can be detoxified anaerobically in cells. In order to elucidate the mechanism of this enzyme, model complexes provide a convenient means to assess potential reaction intermediates. In particular, there have been many proposed mechanisms that invoke the formation of a Hyponitrite bridge between the heme b3 and nonheme iron (FeB) centers within the NorBC active site. However, the reactivity of bridged iron Hyponitrite complexes has not been investigated much in the literature. The model complex {[Fe(OEP)]2(μ-N2O2)} offers a unique opportunity to study the electronic structure and reactivity of such a Hyponitrite-bridged complex. Here we report the detailed characterization of {[Fe(OEP)]2(μ-N2O2)} using a combination of IR, nuclear resonance vibrational spectroscopy, electron paramagnetic resonance, and magnetic circular dichroism spectroscopy along with SQUID magnetometry. These results show that the ground-state electronic structure of this complex is best described as having two intermediate-spin (S = 3/2) iron centers that are weakly antiferromagnetically coupled across the N2O22– bridge. The analogous complex {[Fe(PPDME)]2(μ-N2O2)} shows overall similar properties. Finally, we report the unexpected reaction of {[Fe(OEP)]2(μ-N2O2)} in the presence and absence of 1-methylimidizole to yield [Fe(OEP)(NO)]. Density functional theory calculations are used to rationalize why {[Fe(OEP)]2(μ-N2O2)} cannot be formed directly by dimerization of [Fe(OEP)(NO)] and why only the reverse reaction is observed experimentally. These results thus provide insight into the general reactivity of Hyponitrite-bridged iron complexes with general relevance for the N–N bond-forming step in NorBC
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Linkage Isomerization in Heme−NOx Compounds: Understanding NO, Nitrite, and Hyponitrite Interactions with Iron Porphyrins
Inorganic chemistry, 2010Co-Authors: George B. Richter-addoAbstract:Nitric oxide (NO) and its derivatives such as nitrite and Hyponitrite are biologically important species of relevance to human health. Much of their physiological relevance stems from their interactions with the iron centers in heme proteins. The chemical reactivities displayed by the heme−NOx species (NOx = NO, nitrite, Hyponitrite) are a function of the binding modes of the NOx ligands. Hence, an understanding of the types of binding modes extant in heme−NOx compounds is important if we are to unravel the inherent chemical properties of these NOx metabolites. In this Forum Article, the experimentally characterized linkage isomers of heme−NOx models and proteins are presented and reviewed. Nitrosyl linkage isomers of synthetic iron and ruthenium porphyrins have been generated by photolysis at low temperatures and characterized by spectroscopy and density functional theory calculations. Nitrite linkage isomers in synthetic metalloporphyrin derivatives have been generated from photolysis experiments and in...
Elizabeth S. Sagan - One of the best experts on this subject based on the ideXlab platform.
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Correlation of the Product E/Z Framework Geometry and O/O vs O/N Regioselectivity in the Dialkylation of Hyponitrite
Journal of the American Chemical Society, 2000Co-Authors: Navamoney Arulsamy, D. Scott Bohle, And Jerome A. Imonigie, Elizabeth S. SaganAbstract:The products from the alkylation of silver Hyponitrite with tert-butyl bromide, tert-amyl bromide, p-tert-butyl benzylbromide, and chlorotriethylsilane have been determined. In the reaction of tert-butyl bromide the formation of three new products, namely, (Z)-N-tert-butyl-N‘-tert-butoxydiazene-N-oxide {(CH3)3CN(O)NOC(CH3)3}, 1D, trans-mono-O-tert-butylhyponitrous acid {(CH3)3CONNOH}, 2A, and (Z)-N-tert-butyl-N‘-hydroxydiazene-N-oxide {(CH3)3CN(O)NNOH}, 2D, is observed together with the formation of the known trans-di-O-tert-butyl Hyponitrite {(CH3)3CONNOC(CH3)3}, 1A. The reaction with tert-amyl bromide also yielded the corresponding tert-amyl derivatives. However, from the reactions of p-tert-butylbenzyl bromide and chlorotriethylsilane with silver Hyponitrite, the corresponding trans-di-O-tert-alkylHyponitrites were obtained as the only alkylated products. The differential reactivity of the two sets of halides with silver Hyponitrite is explained in terms of the higher stability of the cations generated...
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SYNTHESIS AND CHARACTERIZATION OF ALKYLAMMONIUM HyponitriteS AND BASE-STABILIZED HYPONITROUS ACID SALTS
Inorganic Chemistry, 1999Co-Authors: Navamoney Arulsamy, D. Scott Bohle, Jerome A. Imonigie, Elizabeth S. SaganAbstract:A number of alkylammonium and bipyridinium salts of hyponitrous acid, namely, N,N,N‘,N‘-tetraethylethylenediammonium (3 and 4), N,N,N‘,N‘-tetramethylethylenediammonium (5), triethylenediammonium (6), diquinuclidinium (7), 2,2‘-bipyridinium (8), 4,4‘-bipyridinium (9), 4,4‘-trimethylenebis(1-methylpiperidinium) (10), 4,4‘-trimethylenepiperidinium (11), and bis(triethylammonium) (12) Hyponitrite salts, have been synthesized by the reaction of the corresponding amine in either anhydrous diethyl ether or absolute ethanol with hyponitrous acid solution in anhydrous diethyl ether. Single-crystal X-ray crystallographic data were obtained for sodium Hyponitrite (1), and the thermal decomposition behavior of the salt was examined. The new salts were characterized by IR and Raman spectroscopic data and elemental analyses. Compounds 4 and 7−9 were also characterized by single-crystal X-ray crystallography. The Hyponitrite anions in 1 and 7−9 exhibit similar structural features. The anions are planar with average NN a...
Navamoney Arulsamy - One of the best experts on this subject based on the ideXlab platform.
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Group 8 and 10 Hyponitrite and dinitrosyl complexes
Polyhedron, 2007Co-Authors: Navamoney Arulsamy, D. Scott Bohle, Jerome A. Imonigie, Raecca C. MooreAbstract:Abstract cis-Hyponitrite complexes LnM(N2O2) (M = Ni, Pt; Ln = PPh3, PPh2Me, dppe, and dppf) of divalent group 10 metals have been previously shown to be readily prepared by treating the corresponding LnMCl2 derivatives with sodium-(Z)-1-{4-(2,6-di-tert-butyl-4-methoxycyclohexadienonyl)}diazen-1-ium-1,2-diolate. These complexes adopt a diamagnetic square planar geometry with oxygen bound chelating planar cis-Hyponitrite ligands. They are readily prepared at room temperature but thermally decompose above 90 °C with release of nitrous oxide. Electrophiles such as iodine, methyltriflate, and hydrochloric acid also react rapidly with the cis-Hyponitrite complexes to give nitrous oxide. The structure of one of these previously prepared complexes, (PPh3)2Pt(N2O2), has been redetermined at −100 °C as a dichloromethane solvate with improved precision. The related tetrahedral group 8 dinitrosyl complexes, (PPh3)2M(NO)2 (M = Ru, Os; Ln = PPh3, dppe, and dppf) have been reexamined and new derivatives with chelating phosphines have been prepared by ligand substitution on the corresponding (PPh3)2M(NO)2. The structures of Ru(dppf)(NO)2 and Os(dppe)(NO)2 have been determined. These two analogous families of cis-Hyponitrite and dinitrosyl complexes illustrate the balance of metal dn electron count and nitrosyl redox state with one having linear nitrosyls bound to low valent metal centers, and the former having coupled N 2 O 2 2 - ligands bound to a higher oxidation state metal center.
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Correlation of the Product E/Z Framework Geometry and O/O vs O/N Regioselectivity in the Dialkylation of Hyponitrite
Journal of the American Chemical Society, 2000Co-Authors: Navamoney Arulsamy, D. Scott Bohle, And Jerome A. Imonigie, Elizabeth S. SaganAbstract:The products from the alkylation of silver Hyponitrite with tert-butyl bromide, tert-amyl bromide, p-tert-butyl benzylbromide, and chlorotriethylsilane have been determined. In the reaction of tert-butyl bromide the formation of three new products, namely, (Z)-N-tert-butyl-N‘-tert-butoxydiazene-N-oxide {(CH3)3CN(O)NOC(CH3)3}, 1D, trans-mono-O-tert-butylhyponitrous acid {(CH3)3CONNOH}, 2A, and (Z)-N-tert-butyl-N‘-hydroxydiazene-N-oxide {(CH3)3CN(O)NNOH}, 2D, is observed together with the formation of the known trans-di-O-tert-butyl Hyponitrite {(CH3)3CONNOC(CH3)3}, 1A. The reaction with tert-amyl bromide also yielded the corresponding tert-amyl derivatives. However, from the reactions of p-tert-butylbenzyl bromide and chlorotriethylsilane with silver Hyponitrite, the corresponding trans-di-O-tert-alkylHyponitrites were obtained as the only alkylated products. The differential reactivity of the two sets of halides with silver Hyponitrite is explained in terms of the higher stability of the cations generated...
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SYNTHESIS AND CHARACTERIZATION OF ALKYLAMMONIUM HyponitriteS AND BASE-STABILIZED HYPONITROUS ACID SALTS
Inorganic Chemistry, 1999Co-Authors: Navamoney Arulsamy, D. Scott Bohle, Jerome A. Imonigie, Elizabeth S. SaganAbstract:A number of alkylammonium and bipyridinium salts of hyponitrous acid, namely, N,N,N‘,N‘-tetraethylethylenediammonium (3 and 4), N,N,N‘,N‘-tetramethylethylenediammonium (5), triethylenediammonium (6), diquinuclidinium (7), 2,2‘-bipyridinium (8), 4,4‘-bipyridinium (9), 4,4‘-trimethylenebis(1-methylpiperidinium) (10), 4,4‘-trimethylenepiperidinium (11), and bis(triethylammonium) (12) Hyponitrite salts, have been synthesized by the reaction of the corresponding amine in either anhydrous diethyl ether or absolute ethanol with hyponitrous acid solution in anhydrous diethyl ether. Single-crystal X-ray crystallographic data were obtained for sodium Hyponitrite (1), and the thermal decomposition behavior of the salt was examined. The new salts were characterized by IR and Raman spectroscopic data and elemental analyses. Compounds 4 and 7−9 were also characterized by single-crystal X-ray crystallography. The Hyponitrite anions in 1 and 7−9 exhibit similar structural features. The anions are planar with average NN a...