201
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De A, Mandal S, Mukherjee R. Modeling tyrosinase activity. Effect of ligand topology on aromatic ring hydroxylation: An overview. J Inorg Biochem 2008; 102:1170-89. [DOI: 10.1016/j.jinorgbio.2008.01.030] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2007] [Revised: 01/18/2008] [Accepted: 01/21/2008] [Indexed: 10/22/2022]
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202
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Utz D, Kisslinger S, Hampel F, Schindler S. Syntheses and characterization of copper complexes with the ligand 2-aminoethyl(2-pyridylmethyl)-1,2-ethanediamine (apme). J Inorg Biochem 2008; 102:1236-45. [DOI: 10.1016/j.jinorgbio.2008.01.028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2007] [Revised: 01/15/2008] [Accepted: 01/16/2008] [Indexed: 10/22/2022]
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203
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Comba P, Kerscher M, Schiek W. Bispidine Coordination Chemistry. PROGRESS IN INORGANIC CHEMISTRY 2008. [DOI: 10.1002/9780470144428.ch9] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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204
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Zhou L, Nicholas KM. Imidazole Substituent Effects on Oxidative Reactivity of Tripodal(imid)2(thioether)CuI Complexes. Inorg Chem 2008; 47:4356-67. [DOI: 10.1021/ic800007t] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Lei Zhou
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019
| | - Kenneth M. Nicholas
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019
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205
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Cramer CJ, Gour JR, Kinal A, Włoch M, Piecuch P, Moughal Shahi AR, Gagliardi L. Stereoelectronic Effects on Molecular Geometries and State-Energy Splittings of Ligated Monocopper Dioxygen Complexes. J Phys Chem A 2008; 112:3754-67. [DOI: 10.1021/jp800627e] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Christopher J. Cramer
- Department of Chemistry and Supercomputer Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, Department of Chemistry and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, Department of Chemistry, Ege University, 35100 Bornova/Izmir, Turkey, and Department of Physical Chemistry, Sciences II University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Jeffrey R. Gour
- Department of Chemistry and Supercomputer Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, Department of Chemistry and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, Department of Chemistry, Ege University, 35100 Bornova/Izmir, Turkey, and Department of Physical Chemistry, Sciences II University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Armagan Kinal
- Department of Chemistry and Supercomputer Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, Department of Chemistry and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, Department of Chemistry, Ege University, 35100 Bornova/Izmir, Turkey, and Department of Physical Chemistry, Sciences II University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Marta Włoch
- Department of Chemistry and Supercomputer Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, Department of Chemistry and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, Department of Chemistry, Ege University, 35100 Bornova/Izmir, Turkey, and Department of Physical Chemistry, Sciences II University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Piotr Piecuch
- Department of Chemistry and Supercomputer Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, Department of Chemistry and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, Department of Chemistry, Ege University, 35100 Bornova/Izmir, Turkey, and Department of Physical Chemistry, Sciences II University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Abdul Rehaman Moughal Shahi
- Department of Chemistry and Supercomputer Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, Department of Chemistry and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, Department of Chemistry, Ege University, 35100 Bornova/Izmir, Turkey, and Department of Physical Chemistry, Sciences II University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - Laura Gagliardi
- Department of Chemistry and Supercomputer Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, Department of Chemistry and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, Department of Chemistry, Ege University, 35100 Bornova/Izmir, Turkey, and Department of Physical Chemistry, Sciences II University of Geneva, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
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206
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Rolff M, Tuczek F. Wie hydroxylieren Kupferenzyme aliphatische Substrate? Jüngste Erkenntnisse aus der Chemie synthetischer Modellsysteme. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200705533] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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207
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Rolff M, Tuczek F. How Do Copper Enzymes Hydroxylate Aliphatic Substrates? Recent Insights from the Chemistry of Model Systems. Angew Chem Int Ed Engl 2008; 47:2344-7. [DOI: 10.1002/anie.200705533] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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208
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Kunishita A, Ishimaru H, Nakashima S, Ogura T, Itoh S. Reactivity of mononuclear alkylperoxo copper(II) complex. O-O bond cleavage and C-H bond activation. J Am Chem Soc 2008; 130:4244-5. [PMID: 18335943 DOI: 10.1021/ja800443s] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A detailed reactivity study has been carried out for the first time on a new mononuclear alkylperoxo copper(II) complex, which is generated by the reaction of copper(II) complex supported by the bis(pyridylmethyl)amine tridentate ligand containing a phenyl group at the 6-position of the pyridine donor groups and cumene hydroperoxide (CmOOH) in CH3CN. The cumylperoxo copper(II) complex thus obtained has been found to undergo homolytic cleavage of the O-O bond and induce C-H bond activation of exogenous substrates, providing important insights into the catalytic mechanism of copper monooxygenases.
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Affiliation(s)
- Atsushi Kunishita
- Department of Chemistry, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
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209
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Maiti D, Lee DH, Gaoutchenova K, Würtele C, Holthausen M, Narducci Sarjeant A, Sundermeyer J, Schindler S, Karlin K. Reactions of a Copper(II) Superoxo Complex Lead to CH and OH Substrate Oxygenation: Modeling Copper-Monooxygenase CH Hydroxylation. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200704389] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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210
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Astner J, Weitzer M, Foxon SP, Schindler S, Heinemann FW, Mukherjee J, Gupta R, Mahadevan V, Mukherjee R. Syntheses, characterization, and reactivity of copper complexes with tridentate N-donor ligands. Inorganica Chim Acta 2008. [DOI: 10.1016/j.ica.2007.07.018] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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211
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Fujii T, Yamaguchi S, Hirota S, Masuda H. H-atom abstraction reaction for organic substrates via mononuclear copper(ii)-superoxo species as a model for DβM and PHM. Dalton Trans 2008:164-70. [DOI: 10.1039/b712572k] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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212
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Maiti D, Lee DH, Gaoutchenova K, Würtele C, Holthausen M, Narducci Sarjeant A, Sundermeyer J, Schindler S, Karlin K. Reactions of a Copper(II) Superoxo Complex Lead to CH and OH Substrate Oxygenation: Modeling Copper-Monooxygenase CH Hydroxylation. Angew Chem Int Ed Engl 2008; 47:82-5. [DOI: 10.1002/anie.200704389] [Citation(s) in RCA: 188] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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213
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Lanci MP, Smirnov VV, Cramer CJ, Gauchenova EV, Sundermeyer J, Roth JP. Isotopic probing of molecular oxygen activation at copper(I) sites. J Am Chem Soc 2007; 129:14697-709. [PMID: 17960903 DOI: 10.1021/ja074620c] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Copper-dioxygen (CuO2) adducts are frequently proposed as intermediates in enzymes, yet their electronic and vibrational structures have not always been understood. [Cu(eta1-O2)TMG3tren]+ (TMG3tren = 1,1,1-tris{2-[N2-(1,1,3,3-tetramethylguanidino)]ethyl}amine) features end-on (eta1) O2 coordination in the solid state. Described here is an investigation of the compound's solution properties by nuclear magnetic resonance spectroscopy, density functional calculations, and oxygen isotope effects. The study yields two major findings. First, [Cu(eta1-O2)TMG3tren]+ is paramagnetic due to a triplet electronic structure; this is in contrast to other copper compounds where O2 is bound in a side-on manner. Second, the oxygen equilibrium isotope effect upon O2 binding to copper(I) (18O EIE [triple bond] K(16O16O)/K(16O18O) = 1.0148 +/- 0.0012) is significantly larger than those determined for iron and cobalt eta1-O2 adducts. This result is suggested to reflect greater ionic (CuII-O2-I) character within the valence bond description. A revised interpretation of the physical origins of the 18O EIEs upon O2 binding to redox metals is also advanced along with experimental data that should be used as benchmarks for interpreting 18O kinetic isotope effects upon enzyme reactions.
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Affiliation(s)
- Michael P Lanci
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA
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214
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Müller J, Würtele C, Walter O, Schindler S. Umwandlung eines Nitrils in Cyanid und Aldehyd unter Verwendung von Sauerstoff und einem Cobalt(II)-Komplex. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200701408] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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215
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Müller J, Würtele C, Walter O, Schindler S. Transformation of Nitrile to Cyanide and Aldehyde Using a Cobalt(II) Complex and Dioxygen. Angew Chem Int Ed Engl 2007; 46:7775-7. [PMID: 17847155 DOI: 10.1002/anie.200701408] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Jörg Müller
- Institut für Anorganische und Analytische Chemie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 58, 35392 Giessen, Germany
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216
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Comba P, Knoppe S, Martin B, Rajaraman G, Rolli C, Shapiro B, Stork T. Copper(II)-Mediated Aromaticortho-Hydroxylation: A Hybrid DFT and Ab Initio Exploration. Chemistry 2007; 14:344-57. [PMID: 17907133 DOI: 10.1002/chem.200700865] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Mechanistic pathways for the aromatic hydroxylation by [CuII(L1)(TMAO)(O)](-) (L1=hippuric acid, TMAO=trimethylamine N-oxide), derived from the O--N bond homolysis of its [CuII(L1)(TMAO)2] precursor, were explored by using hybrid density functional theory (B3LYP) and highly correlated ab initio methods (QCISD and CCSD). Published experimental studies suggest that the catalytic reaction is triggered by a terminal copper-oxo species, and a detailed study of electronic structures, bonding, and energetics of the corresponding electromers is presented. Two pathways, a stepwise and a concerted reaction, were considered for the hydroxylation process. The results reveal a clear preference for the concerted pathway, in which the terminal oxygen atom directly attacks the carbon atom of the benzene ring, leading to the ortho-selectively hydroxylated product. Solvent effects were probed by using the PCM and CPCM solvation models, and the PCM model was found to perform better in the present case. Excellent agreement between the experimental and computational results was found, in particular also for changes in reactivity with derivatives of L1.
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Affiliation(s)
- Peter Comba
- Universität Heidelberg, Anorganisch-Chemisches Institut, INF 270, 69120 Heidelberg, Germany.
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217
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Zhou L, Powell D, Nicholas KM. Tripodal Bis(imidazole) Thioether Copper(I) Complexes: Mimics of the CuM Site of Copper Hydroxylase Enzymes. Inorg Chem 2007; 46:7789-99. [PMID: 17713902 DOI: 10.1021/ic700447k] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Tripodal bis(imidazole) thioether ligands, (N-methyl-4,5-diphenyl-2-imidazolyl)2C(OR)C(CH3)2SR' (BIT(OR,SR'); R = H, CH3; R' = CH3, C(CH3)3, C(C6H5)3), have been prepared, offering the same N2S donor atom set as the CuM binding site of the hydroxylase enzymes, dopamine beta hydroxylase and peptidylglycine hydroxylating monooxygenase. Isolable copper(I) complexes of the type [(BIT(OR,SMe))Cu(CO)]PF6 (3a and 3b) are produced in reactions of the respective tripodal ligands 1a (R = H) and 1b (R = Me) with [Cu(CH3CN)4]PF6 in CH2Cl2 under CO (1 atm); the pyramidal structure of 3a has been determined crystallographically. The infrared (IR) nu(CO)'s of 3a and 3b (L = CO) are comparable to those of the Cu(M)-carbonylated enzymes, indicating similar electronic character at the copper centers. The reaction of [(BIT(OH,SMe))Cu(CH3CN)]PF6 (2a) with dioxygen produces [(BIT(O,SOMe))2Cu2(DMF)2](PF6)2 (4), whose X-ray structure revealed the presence of bridging BIT-alkoxo ligands and terminal -SOMe groups. In contrast, oxygenation of 2b (R = Me) affords crystallographically defined [(BIT(OMe,SMe))2Cu2(mu-OH)2](OTf)2 (5), in which the copper centers are oxygenated without accompanying sulfur oxidation. Complex 5 in DMF is transformed into five-coordinate, mononuclear [CuII(BIT(OMe,SMe))(DMF)2](PF6)2 (6). The sterically hindered BIT(OR,SR') ligands 9 and 10 (R' = t-Bu; R = H, Me) and 11 and 12 (R' = CPh3; R = H, Me) were also prepared and examined for copper coordination/oxygenation. Oxygenation of copper(I) complex 13b derived from the BIT(OMe,SBu-t) ligand is slow, relative to 2b, producing a mixture of (BIT(OMe,SBu-t))2Cu2(mu-OH)2-type complexes 14b and 15b in which the -SBu-t group is uncoordinated; one of these complexes (15b) has been ortho-oxygenated on a neighboring aryl group according to the X-ray analysis and characterization of the free ligand. Oxygenation of the copper(I) complex derived from BIT(OMe,SCPh3) ligand 12 produces a novel dinuclear disulfide complex, [(BIT(OMe,S)2Cu2(mu-OH)2](PF6)2 (17), which is structurally characterized. Reactivity studies under anaerobic conditions in the presence of t-BuNC indicate that 17 is the result of copper(I)-induced detritylation followed by oxygenation of a highly reactive copper(I)-thiolate complex.
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Affiliation(s)
- Lei Zhou
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, USA
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218
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Cramer CJ, Tolman WB. Mononuclear Cu-O2 complexes: geometries, spectroscopic properties, electronic structures, and reactivity. Acc Chem Res 2007; 40:601-8. [PMID: 17458929 PMCID: PMC2593863 DOI: 10.1021/ar700008c] [Citation(s) in RCA: 321] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Using interwoven experimental and theoretical methods, detailed studies of several structurally defined 1:1 Cu-O 2 complexes have provided important fundamental chemical information useful for understanding the nature of intermediates involved in aerobic oxidations in synthetic and enzymatic copper-mediated catalysis. In particular, these studies have shed new light on the factors that influence the mode of O 2 coordination (end-on vs side-on) and the electronic structure, which can vary between Cu(II)-superoxo and Cu(III)-peroxo extremes.
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Affiliation(s)
- Christopher J Cramer
- Department of Chemistry, Supercomputer Institute, and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street Southeast, Minneapolis, Minnesota 55410, USA.
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219
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Suzuki M. Ligand effects on dioxygen activation by copper and nickel complexes: reactivity and intermediates. Acc Chem Res 2007; 40:609-17. [PMID: 17559187 DOI: 10.1021/ar600048g] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Copper and nickel complexes having various active-oxygen species M n -O 2 ( n = 1 or 2), such as trans-(micro-1,2-peroxo)Cu (II) 2, bis(micro-oxo)M (III) 2, bis(micro-superoxo)Ni (II) 2, and ligand-based alkylperoxo-M (II) n , can be produced by a series of tetradentate tripodal ligands (TMPA analogues) containing sterically demanding 6-methyl substituent(s) on the pyridyl group(s), where TMPA = tris(2-pyridylmethyl)amine. Roles of the methyl substituent(s) for the formation of the active-oxygen species and their oxidation reactivities are reported.
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Affiliation(s)
- Masatatsu Suzuki
- Department of Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
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220
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Bollinger JM, Krebs C. Enzymatic C–H activation by metal–superoxo intermediates. Curr Opin Chem Biol 2007; 11:151-8. [PMID: 17374503 DOI: 10.1016/j.cbpa.2007.02.037] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2007] [Accepted: 02/22/2007] [Indexed: 11/17/2022]
Abstract
The mechanisms of four enzymes that initiate oxidation of their substrates by using mid-valent metal-superoxo intermediates, rather than the more frequently described high-valent iron-oxo complexes, to cleave relatively strong C-H bonds have come into focus in the past several years. In two of these reactions, the alternative manifold for O2 and C-H activation enables unique four-electron oxidation reactions, thus significantly augmenting Nature's arsenal for transformation of aliphatic carbon compounds. General principles of this alternative manifold, including common kinetic characteristics and thermodynamic limitations, are emerging. Recent, combined experimental and computational studies on other systems have shown how a more thorough understanding of the structures of the metal-superoxo intermediates and the mechanisms by which they cleave C-H bonds might be achieved.
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Affiliation(s)
- J Martin Bollinger
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA.
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221
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222
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Tamm M, Petrovic D, Randoll S, Beer S, Bannenberg T, Jones PG, Grunenberg J. Structural and theoretical investigation of 2-iminoimidazolines ? carbene analogues of iminophosphoranes. Org Biomol Chem 2007; 5:523-30. [PMID: 17252136 DOI: 10.1039/b615418b] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The preparation of 2-iminoimidazolines - has been accomplished by the Staudinger reaction of the carbenes 1,3-di-tert-butylimidazolin-2-ylidene (), 1,3-diisopropyl-4,5-dimethylimidazolin-2-ylidene (), 1,3-diisopropylimidazolin-2-ylidene (), 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (), 1,3-bis(2,6-diisopropylphenylimidazolin-2-ylidene () and 1,3,4,5-tetramethylimidazolin-2-ylidene () with trimethylsilyl azide (Me3SiN3) followed by desilylation of the resulting 2-trimethylsilyliminoimidazolines -. The X-ray crystal structures of and have been established, revealing C1-N1-Si1 angles that are more obtuse than the corresponding P-N-Si angles observed in related trimethylsilyl iminophosphoranes. Together with , the disilylated side product 1,3-diisopropyl-2-(trimethylsilylimino)-4-trimethylsilylimidazoline () has been isolated and structurally characterized. Cleavage of the N-Si bonds in and formation of is easily achieved by stirring in methanol. The molecular structures of the 2-iminoimidazolines are reported, indicating that the structural parameters are best described by non-ylidic resonance structures and that electron delocalization within the imidazole heterocycle does not play a crucial role in these imine systems. Compound forms a head-to-head dimer in the solid state via weak intermolecular N-H...N contacts, which have additionally been characterized by means of compliance constants. To further analyze the electronic structure of these imines in comparison to related guanidine ligands, the proton affinities (PAs) of the model compounds 2-imino-1,3-dimethylimidazoline (), 2-imino-1,3-dimethylimidazolidine () and tetramethylguanidine () have been calculated by means of density functional theory. Finally, the charge distribution in - and the relative contribution of relevant resonance structures have been determined using natural bond orbitals (NBO) and natural resonance theory (NRT).
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Affiliation(s)
- Matthias Tamm
- Institut für Anorganische und Analytische Chemie, Technische Universität Carolo-Wilhelmina zu Braunschweig, Hagenring 30, D-38106 Braunschweig, Germany.
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223
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Petrovic D, Bannenberg T, Randoll S, Jones PG, Tamm M. Synthesis and reactivity of copper(i) complexes containing a bis(imidazolin-2-imine) pincer ligand. Dalton Trans 2007:2812-22. [PMID: 17592598 DOI: 10.1039/b703183a] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The new pincer ligand 2,6-bis[(1,3-di-tert-butylimidazolin-2-imino)methyl]pyridine (TL(tBu)) has been prepared in high yield from 2,6-bis(hydroxymethyl)pyridine (1) and 1,3-di-tert-butylimidazolin-2-imine (3). Reaction of TL(tBu) with [Cu(MeCN)4]PF6 affords the highly reactive copper(I) complex [(TL(tBu))Cu]PF6, [5]PF6, which forms the stable copper(I) isocyanide complexes [6a]PF6 (nu(CN) = 2179 cm(-1)) and [6b]PF6 (nu(CN) = 2140 cm(-1)) upon addition of tert-butyl or 2,6-dimethylphenyl isocyanide, respectively. For the cations 6a and 6b, DFT calculations reveal ground-state electronic structures of the type [(TL(tBu)-kappaN(1):kappaN(2))Cu(CNR)] with tricoordinate geometries around the copper atoms. Exposure of [5]PF6 to the air readily leads to trapping of atmospheric CO2 to form the square-planar complex [(TL(tBu))Cu(HCO3-kappaO)]PF6, [7]PF6, with the bicarbonate ligand adopting a rarely observed monodentate coordination mode. In chlorinated solvents such as dichloromethane or chloroform, [5]PF(6) rapidly abstracts chloride by reductive dechlorination of the solvent to yield [(TL(tBu))CuCl]PF6, [8]PF6 quantitatively. Reaction of TL(tBu) with copper(I) bromide or chloride affords complexes 9a and 9b, respectively, for which X-ray diffraction analysis, low-temperature NMR experiments and DFT calculations reveal the presence of a kappa(2)-coordinated ligand of the type [(TL(tBu)-kappaN(1):kappaN(2))CuX]. In solution, complex 9b undergoes slow disproportionation forming the mixed-valence copper(II)/copper(I) system [(TL(tBu))CuCl][CuCl2], [8]CuCl2 with a linear dichlorocuprate(I) counterion.
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Affiliation(s)
- Dejan Petrovic
- Institut für Anorganische und Analytische Chemie, Technische Universität Carolo-Wilhelmina zu Braunschweig, Hagenring 30, D-38106 Braunschweig, Germany
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224
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Lyashenko G, Saischek G, Pal A, Herbst-Irmer R, Mösch-Zanetti NC. Molecular oxygen activation by a molybdenum(iv) monooxo bis(β-ketiminato) complex. Chem Commun (Camb) 2007:701-3. [PMID: 17392955 DOI: 10.1039/b617199k] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Molybdenum(IV) monooxo compound that contains bis(beta-ketiminato) ligands activates molecular oxygen forming a molybdenum(VI) monooxo peroxo compound, representing a new entry into molybdenum peroxo derivatives.
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Affiliation(s)
- Ganna Lyashenko
- Institut für Chemie, Karl-Franzens-Universität Graz, Schubertstr. 1, A-8010 Graz, Austria
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Maiti D, Fry HC, Woertink JS, Vance MA, Solomon EI, Karlin KD. A 1:1 Copper−Dioxygen Adduct is an End-on Bound Superoxo Copper(II) Complex which Undergoes Oxygenation Reactions with Phenols. J Am Chem Soc 2006; 129:264-5. [PMID: 17212392 DOI: 10.1021/ja067411l] [Citation(s) in RCA: 159] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Debabrata Maiti
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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226
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Heppner DE, Gherman BF, Tolman WB, Cramer CJ. Can an ancillary ligand lead to a thermodynamically stable end-on 1 : 1 Cu–O2adduct supported by a β-diketiminate ligand? Dalton Trans 2006:4773-82. [PMID: 17033702 DOI: 10.1039/b608980a] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The finding that dioxygen binds end-on to the Cu(B) site in the crystal structure of a precatalytic complex of peptidylglycine alpha-hydroxylating monooxygenase has spurred the search for biomimetic model complexes exhibiting the same dioxygen coordination. Recent work has not only indicated that sterically hindered beta-diketiminate ligands (L(1)) could support side-on 1 : 1 Cu-O(2) adducts, but also that an end-on L(1)Cu(THF)O(2) structure occurs as an unstable intermediate in the oxygenation mechanism of the Cu(I) complex. In this work, density functional theory and multireference methods are used to determine the potential of ancillary ligands, X, other than THF to yield thermodynamically stable end-on L(1)CuXO(2) species. A diverse set of ligands X, comprising phosphines, thiophene, cyclic ethers, acetonitrile, para-substituted pyridines, N-heterocyclic carbenes, and ligands bearing hydrogen bond donors, has been considered in order to identify ligand characteristics which energetically favor end-on L(1)CuXO(2) over: a) reversion to the Cu(I) complex and dioxygen, b) isomerization to side-on L(1)CuXO(2), and c) decay to L(1)CuO(2) and X. Ancillary ligands with judiciously chosen degrees and orientation of steric bulk and which bear potential hydrogen bond donors to an end-on bound dioxygen moiety most favor oxygenation of L(1)CuX to yield end-on L(1)CuXO(2). Conversion to the side-on isomer can be deterred through the use of a sufficiently bulky ligand X, such as one that is at least the size of a 5-membered ring. Loss of X to give L(1)CuO(2) can be made prohibitively endergonic by employing ligands X which are highly electron donating and which backbond strongly with and sigma-donate significantly to copper.
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Affiliation(s)
- David E Heppner
- Department of Chemistry and Supercomputer Institute, University of Minnesota, Minneapolis, MN 55455, USA
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227
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Fujii T, Yamaguchi S, Funahashi Y, Ozawa T, Tosha T, Kitagawa T, Masuda H. Mononuclear copper(ii)–hydroperoxo complex derived from reaction of copper(i) complex with dioxygen as a model of DβM and PHM. Chem Commun (Camb) 2006:4428-30. [PMID: 17057866 DOI: 10.1039/b609673e] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A mononuclear copper(II)-hydroperoxo species has been generated by the reaction of Cu(I)-H2BPPA complex with dioxygen, which illustrates the enzymatic reaction process of the CuB site in the DbetaM and PHM.
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Affiliation(s)
- Tatsuya Fujii
- Department of Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya, 466-8555, Japan
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228
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Hill LMR, Gherman BF, Aboelella NW, Cramer CJ, Tolman WB. Electronic tuning of β-diketiminate ligands with fluorinated substituents: effects on the O2-reactivity of mononuclear Cu(i) complexes. Dalton Trans 2006:4944-53. [PMID: 17047744 DOI: 10.1039/b609939d] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Copper(i) complexes with the beta-diketiminate ligands HC{C(R)N(Dipp)}{C(R')N(Dipp)}(-) (Dipp = C(6)H(3)(i)Pr(2-)2,6; L(1), R = CF(3), R' = CH(3); L(2), R = R' = CF(3)) have been isolated and fully characterized. On the basis of X-ray structural comparisons with the previously reported complex LCu(CH(3)CN) (L = HC{C(CH(3))N(Dipp)}(2)(-)), the ligand environments at the copper centers in the analogous nitrile adducts with L(1) and L(2) impose similar steric demands. L(1)Cu(CH(3)CN) reacts instantaneously at low temperature with O(2) to form a thermally-unstable intermediate with an isotope-sensitive vibration at 977 cm(-1) (928 cm(-1) with (18)O(2)), in accord with the peroxo O-O stretch associated with side-on coordination for LCu(O(2)). However, L(2)Cu(CH(3)CN) is unreactive toward O(2) even at room temperature. Evaluation of the redox potentials of the nitrile adducts and the CO stretching frequencies of the carbon monoxide adducts revealed an incremental adjustment of the electronic environment at the copper center that correlated with the extent of ligand fluorination. Furthermore, theoretical calculations (DFT, CASPT2) predicted that an increasing extent of Cu(ii)-superoxo character and end-on coordination of the O(2) moiety in the Cu/O(2) product (L(2) > L(1) > L) are accompanied by increases in the free energy for the oxygenation reaction, with L(2) unable to support a Cu/O(2) intermediate. Calculations also predict the 1 : 1 Cu/O(2) adducts to be unreactive with respect to hydrogen atom abstraction from hydrocarbon substrates on the basis of their stability towards both reduction and protonation.
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Affiliation(s)
- Lyndal M R Hill
- Department of Chemistry, Center for Metals in Biocatalysis, and Supercomputer Institute, University of Minnesota, 207 Pleasant St. SE, Minneapolis, 55455-0431, USA
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