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Halfen JA, Young VG. Efficient preparation of 1,4,8-trimethylcyclam and its conversion into a thioalkyl-pendant pentadentate chelate. Chem Commun (Camb) 2003:2894-5. [PMID: 14680228 DOI: 10.1039/b311520h] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A facile synthesis of 1,4,8-trimethylcyclam and a thioalkyl-pendant derivative are reported, and the X-ray crystal structure of a nickel(II) complex illustrates structural consequences of appending the thiolate donor onto the macrocycle.
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Halfen JA, Moore HL, Fox DC. Synthetic models of the reduced active site of superoxide reductase. Inorg Chem 2002; 41:3935-43. [PMID: 12132918 DOI: 10.1021/ic025517l] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report the synthesis, structural and spectroscopic characterization, and magnetic and electrochemical studies of a series of iron(II) complexes of the pyridyl-appended diazacyclooctane ligand L(8)py(2), including several that model the square-pyramidal [Fe(II)(N(his))(4)(S(cys))] structure of the reduced active site of the non-heme iron enzyme superoxide reductase. Combination of L(8)py(2) with FeCl(2) provides [L(8)py(2)FeCl(2)] (1), which contains a trigonal-prismatic hexacoordinate iron(II) center, whereas a parallel reaction using [Fe(H(2)O)(6)](BF(4))(2) provides [L(8)py(2)Fe(FBF(3))]BF(4) (2), a novel BF(4)(-)-ligated square-pyramidal iron(II) complex. Substitution of the BF(4)(-) ligand in 2 with formate or acetate ions affords distorted pentacoordinate [L(8)py(2)Fe(O(2)CH)]BF(4) (3) and [L(8)py(2)Fe(O(2)CCH(3))]BF(4) (4), respectively. Models of the superoxide reductase active site are prepared upon reaction of 2 with sodium salts of aromatic and aliphatic thiolates. These model complexes include [L(8)py(2)Fe(SC(6)H(4)-p-CH(3))]BF(4) (5), [L(8)py(2)Fe(SC(6)H(4)-m-CH(3))]BF(4) (6), and [L(8)py(2)Fe(SC(6)H(11))]BF(4) (7). X-ray crystallographic studies confirm that the iron(II)-thiolate complexes model the square-pyramidal geometry and N(4)S donor set of the reduced active site of superoxide reductase. The iron(II)-thiolate complexes are high spin (S = 2), and their solutions are yellow in color because of multiple charge-transfer transitions that occur between 300 and 425 nm. The ambient temperature cyclic voltammograms of the iron(II)-thiolate complexes contain irreversible oxidation waves with anodic peak potentials that correlate with the relative electron donating abilities of the thiolate ligands. This electrochemical irreversibility is attributed to the bimolecular generation of disulfides from the electrochemically generated iron(III)-thiolate species.
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Mahapatra S, Halfen JA, Wilkinson EC, Que L, Tolman WB. Modeling Copper-Dioxygen Reactivity in Proteins: Aliphatic C-H Bond Activation by a New Dicopper(II)-Peroxo Complex. J Am Chem Soc 2002. [DOI: 10.1021/ja00100a068] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Halfen JA, Tolman WB. Synthetic Model of the Substrate Adduct to the Reduced Active Site of Copper Nitrite Reductase. J Am Chem Soc 2002. [DOI: 10.1021/ja00091a064] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Mahapatra S, Halfen JA, Wilkinson EC, Pan G, Cramer CJ, Que LJ, Tolman WB. A New Intermediate in Copper Dioxygen Chemistry: Breaking the O-O Bond To Form a {Cu2(.mu.-O)2}2+ Core. J Am Chem Soc 2002. [DOI: 10.1021/ja00139a026] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Halfen JA, Mahapatra S, Olmstead MM, Tolman WB. Synthetic Analogs of Nitrite Adducts of Copper Proteins: Characterization and Interconversion of Dicopper(I,I) and -(I,II) Complexes Bridged Only by NO2-. J Am Chem Soc 2002. [DOI: 10.1021/ja00084a079] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Houser RP, Halfen JA, Young VG, Blackburn NJ, Tolman WB. Structural Characterization of the First Example of a Bis(.mu.-thiolato)dicopper(II) Complex. Relevance to Proposals for the Electron Transfer Sites in Cytochrome c Oxidase and Nitrous Oxide Reductase. J Am Chem Soc 2002. [DOI: 10.1021/ja00148a018] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Vyvyan JR, Rubens CA, Halfen JA. Synthesis of the napalilactone and pathylactone A spirocyclic skeleton. Tetrahedron Lett 2002. [DOI: 10.1016/s0040-4039(01)02141-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Halfen JA, Fox DC, Mehn MP, Que L. Enhanced reactivity of copper catalysts for olefin aziridination by manipulation of ligand denticity. Inorg Chem 2001; 40:5060-1. [PMID: 11559056 DOI: 10.1021/ic015551k] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Cutland AD, Halfen JA, Kampf JW, Pecoraro VL. Chiral 15-metallacrown-5 complexes differentially bind carboxylate anions. J Am Chem Soc 2001; 123:6211-2. [PMID: 11414869 DOI: 10.1021/ja015610t] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Krogstad DA, Halfen JA, Terry TJ, Young VG. Synthesis and characterization of iridium 1,3,5-triaza-7-phosphaadamantane (PTA) complexes. X-ray crystal and molecular structures of [Ir(PTA)4(CO)]Cl and [Ir(PTAH)3(PTAH2)(H)2]Cl6. Inorg Chem 2001; 40:463-71. [PMID: 11209602 DOI: 10.1021/ic000501l] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The first 1,3,5-triaza-7-phosphaadamantane (PTA) ligated iridium compounds have been synthesized. The reaction of PTA with [Ir(COD)Cl]2 (COD = 1,5-cyclooctadiene) under a CO atmosphere produces an inseparable mixture of [Ir(PTA)3(CO)Cl] (1) and the PTA analogue of Vaska's compound, [Ir(PTA)2(CO)Cl] (2). Compound 1 and [Ir(PTA)4(CO)]Cl (3) were prepared via ligand substitution reactions of PTA with Vaska's compound, trans-Ir(PPh3)2(CO)Cl, in absolute and 95% ethanol, respectively. Complex 3 crystallizes in the orthorhombic space group Pbca with a = 20.3619(4) A, b = 14.0345(3) A, c = 24.1575(5) A, and Z = 8. Single-crystal X-ray diffraction studies show that 3 has a trigonal bipyramidal structure in which the CO occupies an axial position. This is the first crystallographically characterized [IrP4(CO)]+ complex in which the CO is axially ligated. Compound 1 was converted into 3 by ligand substitution with 1 equiv of PTA in water. Interestingly, the reaction of 3 with excess NaCl did not result in the production of 1, but instead the formation of the dichloro species, [Ir(PTAH)2(PTA)2Cl2]Cl3 (4) (PTAH = protonated PTA). Dissolution of 1 or 3 in dilute HCl produced 4 and a dihydrido species, [Ir(PTAH)4(H)2]Cl5 (5), which were readily separated by inspection due to their different crystal habits. Compound 5 crystallizes in the triclinic space group P1 with a = 12.4432(9) A, b = 12.5921(9) A, c = 16.3231(12) A, alpha = 76.004(1) degrees, beta = 71.605(1) degrees, gamma = 69.177(1) degrees, and Z = 2. Complex 5 exhibits a distorted octahedral geometry with two hydride ligands in a cis configuration. A rationale consistent with these reactions is presented by consideration of the steric and electronic properties of the PTA ligand.
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Chenier PJ, Halfen JA, Raguse TL, Rich AE, Splan KE, Yoshioka K, Hoye TR. SYNTHESIS AND X-RAY CRYSTALLOGRAPHY OF CHIRAL TROPOCORONANDS. SYNTHETIC COMMUN 2001. [DOI: 10.1081/scc-100000574] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Halfen JA, Uhan JM, Fox DC, Mehn MP, Que L. Copper(II) complexes of pyridyl-appended diazacycloalkanes: synthesis, characterization, and application to catalytic olefin aziridination. Inorg Chem 2000; 39:4913-20. [PMID: 11196971 DOI: 10.1021/ic000664+] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
As part of an ongoing effort to rationally design new copper catalysts for olefin aziridination, a family of copper(II) complexes derived from new tetradentate macrocyclic ligands are synthesized, characterized both in the solid state and in solution, and screened for catalytic nitrene transfer reactivity with a representative set of olefins. The pyridylmethyl-appended diazacycloalkane ligands L6(py)2, L7(py)2, and L8(py)2 are prepared by alkylation of the appropriate diazacycloalkane (piperazine, homopiperazine, or diazacyclooctane) with picolyl chloride in the presence of triethylamine. The ligands are metalated with Cu(ClO4)(2).6H2O to provide the complexes [(L6(py)2)Cu(OClO3)]ClO4 (1), [(L7(py)2)Cu(OClO3)]ClO4 (2), and [(L8(py)2)Cu](ClO4)2 (3), which, after metathesis with NH4PF6 in CH3CN, afford [(L6(py)2)Cu(CH3CN)](PF6)2 (4), [(L7(py)2)Cu(CH3CN)](PF6)2 (5), and [(L8(py)2)Cu](PF6)2 (6). All six complexes are characterized by X-ray crystallography, which reveals that complexes supported by L6(py)2 and L7(py)2 (1, 2, 4, 5) adopt square-pyramidal geometries, while complexes 3 and 6, ligated by L8(py)2 feature tetracoordinate, distorted-square-planar copper ions. Tetragonal geometries in solution and d(x2 - y2), ground states are confirmed for the complexes by a combination of UV-visible and EPR spectroscopies. The divergent flexibility of the three supporting ligands influences the Cu(II)/Cu(I) redox potentials within the family, such that the complexes supported by the larger ligands L7(py)2 and L8(py)2 (5 and 6) exhibit quasi-reversible electron transfer processes (E1/2 approximately -0.2 V vs Ag/AgCl), while the complex supported by L6(py)2 (4), which imposes a rigid tetragonal geometry upon the central copper(II) ion, is irreversibly reduced in CH3CN solution. Complexes 4-6 are efficient catalysts (in 5 mol % amounts) for the aziridination of styrene with the iodinane PhINTs (in 80-90% yields vs PhINTs), while only 4 exhibits significant catalytic nitrene transfer reactivity with 1-hexene and cyclooctene.
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Lam BM, Halfen JA, Young VG, Hagadorn JR, Holland PL, Lledós A, Cucurull-Sánchez L, Novoa JJ, Alvarez S, Tolman WB. Ligand macrocycle structural effects on copper-dioxygen reactivity. Inorg Chem 2000; 39:4059-72. [PMID: 11198861 DOI: 10.1021/ic000248p] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
With the goal of understanding how the nature of the tridentate macrocyclic supporting ligand influences the relative stability of isomeric mu-eta 2:eta 2-peroxo- and bis(mu-oxo)dicopper complexes, a comparative study was undertaken of the O2 reactivity of Cu(I) compounds supported by the 10- and 12-membered macrocycles, 1,4,7-R3-1,4,7-triazacyclodecane (R3TACD; R = Me, Bn, iPr) and 1,5,9-triisopropyl-1,5,9-triazacyclododecane (iPr3TACDD). While the 3-coordinate complex [(iPr3TACDD)Cu]SbF6 was unreactive with O2, oxygenation of [(R3TACD)Cu(CH3CN)]X (R = Me or Bn; X = ClO4- or SbF6-) at -80 degrees C yielded bis(mu-oxo) species [(R3TACD)2Cu2(mu O)2]X2 as revealed by UV-vis and resonance Raman spectroscopy. Interestingly, unlike the previously reported system supported by 1,4,7-triisopropyl-1,4,7-triazacyclononane (iPr3TACN), which yielded interconverting mixtures of peroxo and bis(mu-oxo) compounds (Cahoy, J.; Holland, P. L.; Tolman, W. B. Inorg. Chem. 1999, 38, 2161), low-temperature oxygenation of [(iPr3TACD)Cu(CH3CN)]SbF6 in a variety of solvents cleanly yielded a mu-eta 2:eta 2-peroxo product, with no trace of the bis(mu-oxo) isomer. The peroxo complex was characterized by UV-vis and resonance Raman spectroscopy, as well as an X-ray crystal structure (albeit of marginal quality due to disorder problems). Intramolecular attack at the alpha C-H bonds of the substituents was indicated as the primary decomposition pathway of the oxygenated compounds through examination of the decay kinetics and the reaction products, which included bis(mu-hydroxo)- and mu-carbonato-dicopper complexes that were characterized by X-ray diffraction. A rationale for the varying results of the oxygenation reactions was provided by analysis of (a) the X-ray crystal structures and electrochemical behavior of the Cu(I) precursors and (b) the results of theoretical calculations of the complete oxygenated complexes, including all ligand atoms, using combined quantum chemical/molecular mechanics (integrated molecular orbital molecular mechanics, IMOMM) methods. The size of the ligand substituents was shown to be a key factor in controlling the relative stabilities of the peroxo and bis(mu-oxo) forms, and the nature of this influence was shown by both theory and experiment to depend on the ligand macrocycle ring size.
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Berreau LM, Halfen JA, Young VG, Tolman WB. Heterocyclic donor influences on the binding and activation of CO, NO, and O2 by copper complexes of hybrid triazacyclononane–pyridyl ligands. Inorganica Chim Acta 2000. [DOI: 10.1016/s0020-1693(99)00292-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Halfen JA, Hallman JK, Schultz JA, Emerson JP. Remarkably Efficient Olefin Aziridination Mediated by a New Copper(II) Complex. Organometallics 1999. [DOI: 10.1021/om9908579] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Berreau LM, Mahapatra S, Halfen JA, Houser RP, Young VG, Tolman WB. Reaktivität von Peroxo- und Di-μ-oxo-dikupferkomplexen gegenüber Brenzcatechinen. Angew Chem Int Ed Engl 1999. [DOI: 10.1002/(sici)1521-3757(19990115)111:1/2<180::aid-ange180>3.0.co;2-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Berreau LM, Mahapatra S, Halfen JA, Houser RP, Young, Jr. VG, Tolman WB. Reactivity of Peroxo- and Bis(μ-oxo)dicopper Complexes with Catechols. Angew Chem Int Ed Engl 1999. [DOI: 10.1002/(sici)1521-3773(19990115)38:1/2<207::aid-anie207>3.0.co;2-u] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Halfen JA, Bodwin JJ, Pecoraro VL. Preparation and Characterization of Chiral Copper 12-Metallacrown-4 Complexes, Inorganic Analogues of Tetraphenylporphyrinatocopper(II). Inorg Chem 1998; 37:5416-5417. [PMID: 11670682 DOI: 10.1021/ic9807386] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Halfen JA, Young VG, Tolman WB. An Unusual Ligand Oxidation by a (&mgr;-eta(2):eta(2)-Peroxo)dicopper Compound: 1 degrees > 3 degrees C-H Bond Selectivity and a Novel Bis(&mgr;-alkylperoxo)dicopper Intermediate. Inorg Chem 1998; 37:2102-2103. [PMID: 11670360 DOI: 10.1021/ic971216d] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Keyes MC, Chamberlain BM, Caltagirone SA, Halfen JA, Tolman WB. A New Set of Structurally Related Enantiopure Polypyrazolyl Ligands of Varying Rotational Symmetry: Synthesis, Metal Complexation, and Comparison of Asymmetric Induction. Organometallics 1998. [DOI: 10.1021/om9801047] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Berreau LM, Halfen JA, Young VG, Tolman WB. Synthesis and Copper Coordination Chemistry of Hindered 1,4,7-Triazacyclononane Ligands with Amide Appendages. Inorg Chem 1998. [DOI: 10.1021/ic971115f] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Schneider JL, Halfen JA, Young, Jr. VG, Tolman WB. Mono- versus bidentate coordination of the NONOate [Et2N(N2O2)]- to copper(II) complexes of tetradentate ligands. NEW J CHEM 1998. [DOI: 10.1039/a800561c] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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50
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Mahapatra S, Kaderli S, Llobet A, Neuhold YM, Palanché T, Halfen JA, Young, VG, Kaden TA, Que, L, Zuberbühler AD, Tolman WB. Binucleating Ligand Structural Effects on (μ-Peroxo)- and Bis(μ-oxo)dicopper Complex Formation and Decay: Competition between Arene Hydroxylation and Aliphatic C−H Bond Activation. Inorg Chem 1997. [DOI: 10.1021/ic970718o] [Citation(s) in RCA: 122] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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