1
|
Small BL, Rios R, Fernandez ER, Gerlach DL, Halfen JA, Carney MJ. Oligomerization of Ethylene Using New Tridentate Iron Catalysts Bearing α-Diimine Ligands with Pendant S and P Donors. Organometallics 2010. [DOI: 10.1021/om1007743] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Brooke L. Small
- Chevron Phillips Chemical Company, 1862 Kingwood Drive, Kingwood, Texas 77339, United States
| | - Ray Rios
- Chevron Phillips Chemical Company, 1862 Kingwood Drive, Kingwood, Texas 77339, United States
| | - Eric R. Fernandez
- Chevron Phillips Chemical Company, 1862 Kingwood Drive, Kingwood, Texas 77339, United States
| | - Deidra L. Gerlach
- Department of Chemistry, University of Wisconsin−Eau Claire, 105 Garfield Avenue, Eau Claire, Wisconsin 54702, United States
| | - Jason A. Halfen
- Department of Chemistry, University of Wisconsin−Eau Claire, 105 Garfield Avenue, Eau Claire, Wisconsin 54702, United States
| | - Michael J. Carney
- Department of Chemistry, University of Wisconsin−Eau Claire, 105 Garfield Avenue, Eau Claire, Wisconsin 54702, United States
| |
Collapse
|
2
|
Grubel K, Rudzka K, Arif AM, Klotz KL, Halfen JA, Berreau LM. Correction to Synthesis, Characterization, and Ligand Exchange Reactivity of a Series of First Row Divalent Metal 3-Hydroxyflavonolate Complexes. Inorg Chem 2010. [DOI: 10.1021/ic1020115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
3
|
McDonald AR, Bukowski MR, Farquhar ER, Jackson TA, Koehntop KD, Seo MS, De Hont RF, Stubna A, Halfen JA, Münck E, Nam W, Que L. Sulfur versus iron oxidation in an iron-thiolate model complex. J Am Chem Soc 2010; 132:17118-29. [PMID: 21070030 DOI: 10.1021/ja1045428] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In the absence of base, the reaction of [Fe(II)(TMCS)]PF6 (1, TMCS = 1-(2-mercaptoethyl)-4,8,11-trimethyl-1,4,8,11-tetraazacyclotetradecane) with peracid in methanol at -20 °C did not yield the oxoiron(IV) complex (2, [Fe(IV)(O)(TMCS)]PF6), as previously observed in the presence of strong base (KO(t)Bu). Instead, the addition of 1 equiv of peracid resulted in 50% consumption of 1. The addition of a second equivalent of peracid resulted in the complete consumption of 1 and the formation of a new species 3, as monitored by UV-vis, ESI-MS, and Mössbauer spectroscopies. ESI-MS showed 3 to be formulated as [Fe(II)(TMCS) + 2O](+), while EXAFS analysis suggested that 3 was an O-bound iron(II)-sulfinate complex (Fe-O = 1.95 Å, Fe-S = 3.26 Å). The addition of a third equivalent of peracid resulted in the formation of yet another compound, 4, which showed electronic absorption properties typical of an oxoiron(IV) species. Mössbauer spectroscopy confirmed 4 to be a novel iron(IV) compound, different from 2, and EXAFS (Fe═O = 1.64 Å) and resonance Raman (ν(Fe═O) = 831 cm(-1)) showed that indeed an oxoiron(IV) unit had been generated in 4. Furthermore, both infrared and Raman spectroscopy gave indications that 4 contains a metal-bound sulfinate moiety (ν(s)(SO2) ≈ 1000 cm (-1), ν(as)(SO2) ≈ 1150 cm (-1)). Investigations into the reactivity of 1 and 2 toward H(+) and oxygen atom transfer reagents have led to a mechanism for sulfur oxidation in which 2 could form even in the absence of base but is rapidly protonated to yield an oxoiron(IV) species with an uncoordinated thiol moiety that acts as both oxidant and substrate in the conversion of 2 to 3.
Collapse
Affiliation(s)
- Aidan R McDonald
- Department of Chemistry and Center for Metals in Biocatalysis, 207 Pleasant Street SE, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
4
|
Grubel K, Rudzka K, Arif AM, Klotz KL, Halfen JA, Berreau LM. Synthesis, Characterization, and Ligand Exchange Reactivity of a Series of First Row Divalent Metal 3-Hydroxyflavonolate Complexes. Inorg Chem 2009; 49:82-96. [DOI: 10.1021/ic901405h] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Katarzyna Grubel
- Department of Chemistry & Biochemistry, Utah State University, Logan, Utah 84322-0300
| | - Katarzyna Rudzka
- Department of Chemistry & Biochemistry, Utah State University, Logan, Utah 84322-0300
| | - Atta M. Arif
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850
| | - Katie L. Klotz
- Department of Chemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin 54702
| | - Jason A. Halfen
- Department of Chemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin 54702
| | - Lisa M. Berreau
- Department of Chemistry & Biochemistry, Utah State University, Logan, Utah 84322-0300
| |
Collapse
|
5
|
Klotz KL, Slominski LM, Riemer ME, Phillips JA, Halfen JA. Mechanism of the iron-mediated alkene aziridination reaction: experimental and computational investigations. Inorg Chem 2009; 48:801-3. [PMID: 19102690 DOI: 10.1021/ic8020244] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Combined experimental and computational studies suggest that the iron-mediated aziridination of cis-1-phenylpropene proceeds along two mechanistic pathways that share a common imidoiron(IV) intermediate. One pathway involves a second species, proposed to be an azametallacyclobutane intermediate, which collapses to provide the syn-aziridine product. A second, parallel pathway is responsible for the formation of an anti-aziridine.
Collapse
Affiliation(s)
- Katie L Klotz
- Department of Chemistry, University of Wisconsin-Eau Claire, 105 Garfield Avenue, Eau Claire, Wisconsin 54702, USA
| | | | | | | | | |
Collapse
|
6
|
Grove LE, Hallman JK, Emerson JP, Halfen JA, Brunold TC. Synthesis, X-ray crystallographic characterization, and electronic structure studies of a di-azide iron(III) complex: implications for the azide adducts of iron(III) superoxide dismutase. Inorg Chem 2008; 47:5762-74. [PMID: 18533647 PMCID: PMC4316727 DOI: 10.1021/ic800073t] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have synthesized and characterized, using X-ray crystallographic, spectroscopic, and computational techniques, a six-coordinate diazide Fe (3+) complex, LFe(N 3) 2 (where L is the tetradentate ligand 7-diisopropyl-1,4,7-triazacyclononane-1-acetic acid), that serves as a model of the azide adducts of Fe (3+) superoxide dismutase (Fe (3+)SOD). While previous spectroscopic studies revealed that two distinct azide-bound Fe (3+)SOD species can be obtained at cryogenic temperatures depending on protein and azide concentrations, the number of azide ligands coordinated to the Fe (3+) ion in each species has been the subject of some controversy. In the case of LFe(N 3) 2, the electronic absorption and magnetic circular dichroism spectra are dominated by two broad features centered at 21 500 cm (-1) (approximately 4000 M (-1) cm (-1)) and approximately 30 300 cm (-1) (approximately 7400 M (-1) cm (-1)) attributed to N3 (-) --> Fe (3+) charge transfer (CT) transitions. A normal coordinate analysis of resonance Raman (RR) data obtained for LFe(N 3) 2 indicates that the vibrational features at 363 and 403 cm (-1) correspond to the Fe-N 3 stretching modes (nu Fe-N3) associated with the two different azide ligands and yields Fe-N 3 force constants of 1.170 and 1.275 mdyne/A, respectively. RR excitation profile data obtained with laser excitation between 16,000 and 22,000 cm (-1) reveal that the nu Fe-N3 modes at 363 and 403 cm (-1) are preferentially enhanced upon excitation in resonance with the N 3 (-) --> Fe (3+) CT transitions at lower and higher energies, respectively. Consistent with this result, density functional theory electronic structure calculations predict a larger stabilization of the molecular orbitals of the more strongly bound azide due to increased sigma-symmetry orbital overlap with the Fe 3d orbitals, thus yielding higher N 3 (-) --> Fe (3+) CT transition energies. Comparison of our data obtained for LFe(N 3) 2 with those reported previously for the two azide adducts of Fe (3+)SOD provides compelling evidence that a single azide is coordinated to the Fe (3+) center in each protein species.
Collapse
Affiliation(s)
- Laurie E. Grove
- Department of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706
| | - Jason K. Hallman
- Department of Chemistry, University of Wisconsin—Eau Claire, Eau Claire, Wisconsin 54702
| | - Joseph P. Emerson
- Department of Chemistry, University of Wisconsin—Eau Claire, Eau Claire, Wisconsin 54702
| | - Jason A. Halfen
- Department of Chemistry, University of Wisconsin—Eau Claire, Eau Claire, Wisconsin 54702
| | - Thomas C. Brunold
- Department of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706
| |
Collapse
|
7
|
Krogstad DA, Ellis GS, Gunderson AK, Hammrich AJ, Rudolf JW, Halfen JA. Two new water-soluble derivatives of 1,3,5-triaza-7-phosphaadamantane (PTA): Synthesis, characterization, X-ray analysis and solubility studies of 3,7-diformyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane and 1-pyridylmethyl-3,5-diaza-1-azonia-7-phosphatricyclo[3.3.1.1]decane bromide. Polyhedron 2007. [DOI: 10.1016/j.poly.2007.05.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
8
|
Schmiege BM, Carney MJ, Small BL, Gerlach DL, Halfen JA. Alternatives to pyridinediimine ligands: syntheses and structures of metal complexes supported by donor-modified α-diimine ligands. Dalton Trans 2007:2547-62. [PMID: 17563791 DOI: 10.1039/b702197f] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This report describes the synthesis and characterization of metal halide complexes (M = Mn, Fe, Co) supported by a new family of pendant donor-modified alpha-diimine ligands. The donor (N, O, P, S) substituent is linked to the alpha-diimine by a short hydrocarbon spacer forming a tridentate, mer-coordinating ligand structure. The tridentate ligands are assembled from monoimine precursors, the latter being synthesized by selective reaction with one carbonyl group of the alpha-dione. While attempts to separately isolate tridentate ligands in pure form were unsuccessful, metal complexes supported by the tridentate ligand are readily synthesized in-situ, by forming the ligand in the presence of the metal halide, resulting in a metal complex which subsequently crystallizes out of the reaction mixture. Metal complexes with NNN, NNO, NNP and NNS donor sets have been prepared and examples supported by NNN, NNP and NNS ligands have been structurally characterized. In the solid state, NNN and NNP ligands coordinate in a mer fashion and the metal complexes possess distorted square pyramidal structures and high spin (S = 2) electronic configurations. Compounds with NNS coordination environments display a variety of solid state structures, ranging from those with unbound sulfur atoms, including chloride bridged and solvent ligated species, to those with sulfur weakly bound to the metal center. The extent of sulfur ligation depends on the donor ability of the crystallization solvent and the substitution pattern of the arylthioether substituent.
Collapse
Affiliation(s)
- Benjamin M Schmiege
- Department of Chemistry, University of Wisconsin-Eau Claire, 105 Garfield Avenue, Eau Claire, WI 54702, USA
| | | | | | | | | |
Collapse
|
9
|
Klotz KL, Slominski LM, Hull AV, Gottsacker VM, Mas-Ballesté R, Que L, Halfen JA. Non-heme iron(ii) complexes are efficient olefin aziridination catalysts. Chem Commun (Camb) 2007:2063-5. [PMID: 17713079 DOI: 10.1039/b700493a] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Iron(II) complexes of polydentate nitrogen donor ligands catalyze the rapid aziridination of olefins by PhINTs.
Collapse
Affiliation(s)
- Katie L Klotz
- Department of Chemistry, University of Wisconsin-Eau Claire, 105 Garfield Avenue, Eau Claire, WI 54702, USA
| | | | | | | | | | | | | |
Collapse
|
10
|
Krogstad DA, Cho J, DeBoer AJ, Klitzke JA, Sanow WR, Williams HA, Halfen JA. Platinum (II) and palladium (II) 1,3,5-triaza-7-phosphaadamantane (PTA) complexes as intramolecular hydroamination catalysts in aqueous and organic media. Inorganica Chim Acta 2006. [DOI: 10.1016/j.ica.2005.08.028] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
11
|
Phillips JA, Halfen JA, Wrass JP, Knutson CC, Cramer CJ. Large Gas−Solid Structural Differences in Complexes of Haloacetonitriles with Boron Trifluoride. Inorg Chem 2005; 45:722-31. [PMID: 16411708 DOI: 10.1021/ic051491x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The structural properties of the singly halogenated derivatives of CH(3)CN-BF(3) (X-CH(2)CN-BF(3): X = F, Cl, Br, I) have been investigated via single-crystal X-ray crystallography, solid-state infrared spectroscopy, and correlated electronic-structure theory. Taken together, these data illustrate large differences between the gas-phase and solid-state structures of these systems. Calculated gas-phase structures (B3PW91/aug-cc-pVTZ) of FCH(2)CN-BF(3), ClCH(2)CN-BF(3), and BrCH(2)CN-BF(3) indicate that the B-N dative bonds in these systems are quite weak, with distances of 2.422, 2.374, and 2.341 A, respectively. However, these distances, as well as other calculated structural parameters and normal-mode vibrational frequencies, indicate that the dative interactions do become slightly stronger in proceeding from F- to Br-CH(2)CN-BF(3). In contrast, solid-state structures for FCH(2)CN-BF(3), ClCH(2)CN-BF(3), and ICH(2)CN-BF(3) from X-ray crystallography all have B-N distances that are quite short, about 1.65 A. Thus, the B-N distances of the F- and Cl-containing derivatives contract by over 0.7 A upon crystallization. Large shifts in the vibrational modes involving motions of the BF(3) subunit parallel these structural changes. An X-ray crystal structure could not be determined for BrCH(2)CN-BF(3)(s), but the solid-state IR spectrum is consistent with those obtained previously for related complexes and suggests that the solid-state structure resembles those of the others, and in turn, implicates a large gas-solid structural difference for this species as well.
Collapse
Affiliation(s)
- James A Phillips
- Department of Chemistry, University of Wisconsin-Eau Claire, 105 Garfield Avenue, Eau Claire, WI 54701, USA.
| | | | | | | | | |
Collapse
|
12
|
Krogstad DA, DeBoer AJ, Ortmeier WJ, Rudolf JW, Halfen JA. 1,3,5-Triaza-7-phosphaadamantane (PTA) ligated iridium(I) complexes as catalysts for the intramolecular hydroamination of 4-pentyn-1-amine in water. INORG CHEM COMMUN 2005. [DOI: 10.1016/j.inoche.2005.09.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
13
|
Bukowski MR, Koehntop KD, Stubna A, Bominaar EL, Halfen JA, Münck E, Nam W, Que L. A Thiolate-Ligated Nonheme Oxoiron(IV) Complex Relevant to Cytochrome P450. Science 2005; 310:1000-2. [PMID: 16254150 DOI: 10.1126/science.1119092] [Citation(s) in RCA: 219] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Thiolate-ligated oxoiron(IV) centers are postulated to be the key oxidants in the catalytic cycles of oxygen-activating cytochrome P450 and related enzymes. Despite considerable synthetic efforts, chemists have not succeeded in preparing an appropriate model complex. Here we report the synthesis and spectroscopic characterization of [FeIV(O)(TMCS)]+ where TMCS is a pentadentate ligand that provides a square pyramidal N4(SR)apical, where SR is thiolate, ligand environment about the iron center, which is similar to that of cytochrome P450. The rigidity of the ligand framework stabilizes the thiolate in an oxidizing environment. Reactivity studies suggest that thiolate coordination favors hydrogen-atom abstraction chemistry over oxygen-atom transfer pathways in the presence of reducing substrates.
Collapse
Affiliation(s)
- Michael R Bukowski
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN 55455, USA
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Phillips JA, Giesen DJ, Wells NP, Halfen JA, Knutson CC, Wrass JP. Condensed-Phase Effects on the Structural Properties of C6H5CN−BF3 and (CH3)3CCN−BF3: IR Spectra, Crystallography, and Computations. J Phys Chem A 2005; 109:8199-208. [PMID: 16834206 DOI: 10.1021/jp052495q] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Condensed-phase effects on the structure and bonding of C(6)H(5)CN-BF(3) and (CH(3))(3)CCN-BF(3) are illustrated by a variety of results, and these are compared to analogous data for the closely related complex CH(3)CN-BF(3). For the most part, the structural properties of C(6)H(5)CN-BF(3) and (CH(3))(3)CCN-BF(3) are quite similar, not only in the gas phase but also in the solid state and in argon matrices. However, the structures do change significantly from medium to medium, and these changes are reflected in the data presented below. Specifically, the measured crystallographic structure of C(6)H(5)CN-BF(3) (s) has a B-N distance that is 0.17 A shorter than that in the equilibrium gas-phase structure obtained via B3LYP calculations. Notable differences between calculated gas-phase frequencies and measured solid-state frequencies for both C(6)H(5)CN-BF(3) and (CH(3))(3)CCN-BF(3) were also observed, and in the case of (CH(3))(3)CCN-BF(3), these data implicate a comparable difference between solid-state and gas-phase structure, even in the absence of crystallographic results. Frequencies measured in argon matrices were found to be quite similar for both complexes and also very near those measured previously for CH(3)CN-BF(3), suggesting that all three complexes adopt similar structures in solid argon. For C(6)H(5)CN-BF(3) and (CH(3))(3)CCN-BF(3), matrix IR frequencies differ only slightly from the computed gas-phase values, but do suggest a slight compression of the B-N bond. Ultimately, it appears that the varying degree to which these systems respond to condensed phases stems from subtle differences in the gas-phase species, which are highlighted through an examination of B-N distance potentials from B3LYP calculations. The larger organic substituents appear to stabilize the potential near 1.8 A, so that the structures are more localized in that region prior to any condensed-phase interactions. As a result, the condensed-phase effects on the structural properties of C(6)H(5)CN-BF(3) and (CH(3))(3)CCN-BF(3) are much less pronounced than those for CH(3)CN-BF(3).
Collapse
Affiliation(s)
- J A Phillips
- Department of Chemistry, University of Wisconsin-Eau Claire, 105 Garfield Avenue, Eau Claire, WI 54701, USA.
| | | | | | | | | | | |
Collapse
|
15
|
Fiedler AT, Halfen HL, Halfen JA, Brunold TC. Synthesis, Structure Determination, and Spectroscopic/Computational Characterization of a Series of Fe(II)−Thiolate Model Complexes: Implications for Fe−S Bonding in Superoxide Reductases. J Am Chem Soc 2005; 127:1675-89. [PMID: 15701002 DOI: 10.1021/ja046939s] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A combined synthetic/spectroscopic/computational approach has been employed to prepare and characterize a series of Fe(II)-thiolate complexes that model the square-pyramidal [Fe(II)(N(His))(4)(S(Cys))] structure of the reduced active site of superoxide reductases (SORs), a class of enzymes that detoxify superoxide in air-sensitive organisms. The high-spin (S = 2) Fe(II) complexes [(Me(4)cyclam)Fe(SC(6)H(4)-p-OMe)]OTf (2) and [FeL]PF(6) (3) (where Me(4)cyclam = 1,4,8,11-tetramethylcyclam and L is the pentadentate monoanion of 1-thioethyl-4,8,11-trimethylcyclam) were synthesized and subjected to structural, magnetic, and electrochemical characterization. X-ray crystallographic studies confirm that 2 and 3 possess an N(4)S donor set similar to that found for the SOR active site and reveal molecular geometries intermediate between square pyramidal and trigonal bipyramidal for both complexes. Electronic absorption, magnetic circular dichroism (MCD), and variable-temperature variable-field MCD (VTVH-MCD) spectroscopies were utilized, in conjunction with density functional theory (DFT) and semiemperical INDO/S-CI calculations, to probe the ground and excited states of complexes 2 and 3, as well as the previously reported Fe(II) SOR model [(L(8)py(2))Fe(SC(6)H(4)-p-Me)]BF(4) (1) (where L(8)py(2) is a tetradentate pyridyl-appended diazacyclooctane macrocycle). These studies allow for a detailed interpretation of the S-->Fe(II) charge transfer transitions observed in the absorption and MCD spectra of complexes 1-3 and provide significant insights into the nature of Fe(II)-S bonding in complexes with axial thiolate ligation. Of the three models investigated, complex 3 exhibits an absorption spectrum that is particularly similar to the one reported for the reduced SOR enzyme (SOR(red)), suggesting that this model accurately mimics key elements of the electronic structure of the enzyme active site; namely, highly covalent Fe-S pi- and sigma-interactions. These spectral similarities are shown to arise from the fact that 3 contains an alkyl thiolate tethered to the equatorial cyclam ring, resulting in a thiolate orientation that is very similar to the one adopted by the Cys residue in the SOR(red) active site. Possible implications of our results with respect to the electronic structure and reactivity of SOR(red) are discussed.
Collapse
Affiliation(s)
- Adam T Fiedler
- University of Wisconsin-Eau Claire, Department of Chemistry, 105 Garfield Avenue, Eau Claire, WI 54702, USA
| | | | | | | |
Collapse
|
16
|
Bukowski MR, Halfen HL, van den Berg TA, Halfen JA, Que L. Spin-State Rationale for the Peroxo-Stabilizing Role of the Thiolate Ligand in Superoxide Reductase. Angew Chem Int Ed Engl 2005; 44:584-7. [PMID: 15602754 DOI: 10.1002/anie.200461527] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Michael R Bukowski
- Center for Metals in Biocatalysis and Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA
| | | | | | | | | |
Collapse
|
17
|
Bukowski MR, Halfen HL, van den Berg TA, Halfen JA, Que L. Spin-State Rationale for the Peroxo-Stabilizing Role of the Thiolate Ligand in Superoxide Reductase. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200461527] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
18
|
Carney MJ, Robertson NJ, Halfen JA, Zakharov LN, Rheingold AL. Octahedral Chromium(III) Complexes Supported by Bis(2-pyridylmethyl)amines: Ligand Influence on Coordination Geometry and Ethylene Polymerization Activity. Organometallics 2004. [DOI: 10.1021/om0494162] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Michael J. Carney
- Department of Chemistry, University of Wisconsin−Eau Claire, Eau Claire, Wisconsin 54702, and Department of Chemistry and Biochemistry, University of California−San Diego, La Jolla, California 92093-0358
| | - Nicholas J. Robertson
- Department of Chemistry, University of Wisconsin−Eau Claire, Eau Claire, Wisconsin 54702, and Department of Chemistry and Biochemistry, University of California−San Diego, La Jolla, California 92093-0358
| | - Jason A. Halfen
- Department of Chemistry, University of Wisconsin−Eau Claire, Eau Claire, Wisconsin 54702, and Department of Chemistry and Biochemistry, University of California−San Diego, La Jolla, California 92093-0358
| | - Lev N. Zakharov
- Department of Chemistry, University of Wisconsin−Eau Claire, Eau Claire, Wisconsin 54702, and Department of Chemistry and Biochemistry, University of California−San Diego, La Jolla, California 92093-0358
| | - Arnold L. Rheingold
- Department of Chemistry, University of Wisconsin−Eau Claire, Eau Claire, Wisconsin 54702, and Department of Chemistry and Biochemistry, University of California−San Diego, La Jolla, California 92093-0358
| |
Collapse
|
19
|
Horner O, Mouesca JM, Oddou JL, Jeandey C, Nivière V, Mattioli TA, Mathé C, Fontecave M, Maldivi P, Bonville P, Halfen JA, Latour JM. Mössbauer Characterization of an Unusual High-Spin Side-On Peroxo−Fe3+ Species in the Active Site of Superoxide Reductase from Desulfoarculus baarsii. Density Functional Calculations on Related Models. Biochemistry 2004; 43:8815-25. [PMID: 15236590 DOI: 10.1021/bi0498151] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Superoxide reductase (SOR) is an Fe protein that catalyzes the reduction of superoxide to give H(2)O(2). Recently, the mutation of the Glu47 residue into alanine (E47A) in the active site of SOR from Desulfoarculus baarsii has allowed the stabilization of an iron-peroxo species when quickly reacted with H(2)O(2) [Mathé et al. (2002) J. Am. Chem. Soc. 124, 4966-4967]. To further investigate this non-heme peroxo-iron species, we have carried out a Mössbauer study of the (57)Fe-enriched E47A SOR from D. baarsii reacted quickly with H(2)O(2). Considering the Mössbauer data, we conclude, in conjunction with the other spectroscopic data available and with the results of density functional calculations on related models, that this species corresponds to a high-spin side-on peroxo-Fe(3+) complex. This is one of the first examples of such a species in a biological system for which Mössbauer parameters are now available: delta(/Fe) = 0.54 (1) mm/s, DeltaE(Q) = -0.80 (5) mm/s, and the asymmetry parameter eta = 0.60 (5) mm/s. The Mössbauer and spin Hamiltonian parameters have been evaluated on a model from the side-on peroxo complex (model 2) issued from the oxidized iron center in SOR from Pyrococcus furiosus, for which structural data are available in the literature [Yeh et al. (2000) Biochemistry 39, 2499-2508]. For comparison, similar calculations have been carried out on a model derived from 2 (model 3), where the [CH(3)-S](1)(-) group has been replaced by the neutral [NH(3)](0) group [Neese and Solomon (1998) J. Am. Chem. Soc. 120, 12829-12848]. Both models 2 and 3 contain a formally high-spin Fe(3+) ion (i.e., with empty minority spin orbitals). We found, however, a significant fraction ( approximately 0.6 for 2, approximately 0.8 for 3) of spin (equivalently charge) spread over two occupied (minority spin) orbitals. The quadrupole splitting value for 2 is found to be negative and matches quite well the experimental value. The computed quadrupole tensors are rhombic in the case of 2 and axial in the case of 3. This difference originates directly from the presence of the thiolate ligand in 2. A correlation between experimental isomer shifts for Fe(3+) mononuclear complexes with computed electron densities at the iron nucleus has been built and used to evaluate the isomer shift values for 2 and 3 (0.56 and 0.63 mm/s, respectively). A significant increase of isomer shift value is found upon going from a methylthiolate to a nitrogen ligand for the Fe(3+) ion, consistent with covalency effects due to the presence of the axial thiolate ligand. Considering that the isomer shift value for 3 is likely to be in the 0.61-0.65 mm/s range [Horner et al. (2002) Eur. J. Inorg. Chem., 3278-3283], the isomer shift value for a high-spin eta(2)-O(2) Fe(3+) complex with an axial thiolate group can be estimated to be in the 0.54-0.58 mm/s range. The occurrence of a side-on peroxo intermediate in SOR is discussed in relation to the recent data published for a side-on peroxo-Fe(3+) species in another biological system [Karlsson et al. (2003) Science 299, 1039-1042].
Collapse
Affiliation(s)
- Olivier Horner
- Département Réponse et Dynamique Cellulaires, Laboratoire de Physicochimie des Métaux en Biologie, UMR CEA/CNRS/Université Joseph Fourier 5155, France
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Fox DC, Fiedler AT, Halfen HL, Brunold TC, Halfen JA. Electronic Structure Control of the Nucleophilicity of Transition Metal−Thiolate Complexes: An Experimental and Theoretical Study. J Am Chem Soc 2004; 126:7627-38. [PMID: 15198611 DOI: 10.1021/ja039419q] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
New metal(II)-thiolate complexes supported by the tetradentate ligand 1,5-bis(2-pyridylmethyl)-1,5-diazacyclooctane (L(8)py(2)) have been synthesized and subjected to physical, spectroscopic, structural, and computational characterization. The X-ray crystal structures of these complexes, [L(8)py(2)M(S-C(6)H(4)-p-CH(3))]BPh(4) (M = Co, Ni, Zn), reveal distorted square-pyramidal divalent metal ions with four equatorial nitrogen donors from L(8)py(2) and axial p-toluenethiolate ligands. The reactions of the complexes with benzyl bromide produce isolable metal(II)-bromide complexes (in the cases of Co and Ni) and the thioether benzyl-p-tolylsulfide. This reaction is characterized by a second-order rate law (nu = k(2)[L(8)py(2)M(SAr)(+)][PhCH(2)Br]) for all complexes (where M = Fe, Co, Ni, or Zn). Of particular significance is the disparity between k(2) for M = Fe and Co versus k(2) for M = Ni and Zn, in that k(2) for M = Ni and Zn is ca. 10 times larger (faster) than k(2) for M = Fe and Co. An Eyring analysis of k(2) for [L(8)py(2)Co(SAr)](+) and [L(8)py(2)Ni(SAr)](+) reveals that the reaction rate differences are not rooted in a change in mechanism, as the reactions of these complexes with benzyl bromide exhibit comparable activation parameters (M = Co: DeltaH() = 45(2) kJ mol(-)(1), DeltaS() = -144(6) J mol(-)(1) K(-)(1); M = Ni: DeltaH() = 43(3) kJ mol(-)(1), DeltaS() = -134(8) J mol(-)(1) K(-)(1)). Electronic structure calculations using density functional theory (DFT) reveal that the enhanced reaction rate for [L(8)py(2)Ni(SAr)](+) is rooted in a four-electron repulsion (or a "filled/filled interaction") between a completely filled nickel(II) d(pi) orbital and one of the two thiolate frontier orbitals, a condition that is absent in the Fe(II) and Co(II) complexes. The comparable reactivity of [L(8)py(2)Zn(SAr)](+) relative to that of [L(8)py(2)Ni(SAr)](+) arises from a highly ionic zinc(II)-thiolate bond that enhances the negative charge density on the thiolate sulfur. DFT calculations on putative thioether-coordinated intermediates reveal that the Co(II)- and Zn(II)-thioethers exhibit weaker M-S bonding than Ni(II). These combined results suggest that while Ni(II) may serve as a competent replacement for Zn(II) in alkyl group transfer enzymes, turnover may be limited by slow product release from the Ni(II) center.
Collapse
Affiliation(s)
- Derek C Fox
- Department of Chemistry, University of Wisconsin-Madison, 1101 West University Avenue, Madison, Wisconsin 53706, USA
| | | | | | | | | |
Collapse
|
21
|
Small BL, Carney MJ, Holman DM, O'Rourke CE, Halfen JA. New Chromium Complexes for Ethylene Oligomerization: Extended Use of Tridentate Ligands in Metal-Catalyzed Olefin Polymerization. Macromolecules 2004. [DOI: 10.1021/ma035554b] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Brooke L. Small
- Chevron Phillips Chemical Company, LP, 1862 Kingwood Drive, Kingwood, Texas 77339, and Department of Chemistry, University of WisconsinEau Claire, 105 Garfield Avenue, Eau Claire, Wisconsin 54702
| | - Michael J. Carney
- Chevron Phillips Chemical Company, LP, 1862 Kingwood Drive, Kingwood, Texas 77339, and Department of Chemistry, University of WisconsinEau Claire, 105 Garfield Avenue, Eau Claire, Wisconsin 54702
| | - Danah M. Holman
- Chevron Phillips Chemical Company, LP, 1862 Kingwood Drive, Kingwood, Texas 77339, and Department of Chemistry, University of WisconsinEau Claire, 105 Garfield Avenue, Eau Claire, Wisconsin 54702
| | - Colleen E. O'Rourke
- Chevron Phillips Chemical Company, LP, 1862 Kingwood Drive, Kingwood, Texas 77339, and Department of Chemistry, University of WisconsinEau Claire, 105 Garfield Avenue, Eau Claire, Wisconsin 54702
| | - Jason A. Halfen
- Chevron Phillips Chemical Company, LP, 1862 Kingwood Drive, Kingwood, Texas 77339, and Department of Chemistry, University of WisconsinEau Claire, 105 Garfield Avenue, Eau Claire, Wisconsin 54702
| |
Collapse
|
22
|
Coue L, Cuesta L, Morales D, Halfen JA, Pérez J, Riera L, Riera V, Miguel D, Connelly NG, Boonyuen S. A Neutral Organometallic Fluoro Complex Can Be a Good Ligand. Chemistry 2004; 10:1906-12. [PMID: 15079829 DOI: 10.1002/chem.200305706] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The reaction of the complex [Mo(OTf)(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)] (1) (OTf = trifluoromethylsulfonate; phen = 1,10-phenanthroline) with tetrabutylammonium fluoride trihydrate afforded the fluoride complex [MoF(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)] (2). The IR spectrum and the oxidation potential of 2 reflect the fact that its metal center is more electron-rich than that of the chloro analogue [MoCl(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)]. Compound 2 reacted with 1 affording the homobinuclear complex [[Mo(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)](2)(mu-F)][OTf] (3), with a fluoride bridge. Compound 2 also reacts with the species generated in situ by triflate abstraction from [M(OTf)(CO)(3)('N-N')] (M = Mn, Re; 'N-N' = 2,2'-bipyridine (bipy), phen) using NaBAr'(4) (Ar' = 3,5-bis(trifluoromethyl)phenyl), affording the heterobinuclear complexes [[Mo(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)](mu-F)[M(CO)(3)('N--N')]][BAr'(4)] (M = Mn, 'N-N' = bipy (4); M = Re, 'N-N' = phen (5)). All new compounds have been characterized by spectroscopic methods (IR and NMR) and, in the case of 1, 2, 3, and 4, also by means of X-ray diffraction analysis.
Collapse
Affiliation(s)
- Laurent Coue
- Departamento de Química Orgánica e Inorgánica-IUQOEM, Facultad de Química, Universidad de Oviedo-CSIC, 33071 Oviedo, Spain
| | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Tubbs KJ, Szajna E, Bennett B, Halfen JA, Watkins RW, Arif AM, Berreau LM. Mononuclear nitrogen/sulfur-ligated cobalt(ii) methoxide complexes: Structural, EPR, paramagnetic 1H NMR, and electrochemical investigationsElectronic supplementary information (ESI) available: Experimental details, and Figs. S1 (EPR spectra of 1 and 2 in MeOH soln.), S2 and S4 (1H NMR spectra of 1 in CD3CN), S3 and S5 (1H NMR spectra of 2 in CD3CN), S6 (cyclic voltammetry of 1 and 2) and Table S1 (1H NMR features of 1 and 2 in CD3CN at 302 K). See http://www.rsc.org/suppdata/dt/b4/b408177c/. Dalton Trans 2004:2398-9. [PMID: 15303148 DOI: 10.1039/b408177c] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The first examples of mononuclear nitrogen/sulfur-ligated Co(II) alkoxide complexes, species of relevance to a reactive intermediate observed for Co(II)-substituted liver alcohol dehydrogenase, have been isolated and characterized by multiple methods including X-ray crystallography, EPR, paramagnetic (1)H NMR, and cyclic voltammetry.
Collapse
Affiliation(s)
- Kyle J Tubbs
- Department of Chemistry and Biochemistry, Utah State University, 0300 Old Main Hill, Logan, UT 84322-0300, USA
| | | | | | | | | | | | | |
Collapse
|
24
|
Makowska-Grzyska MM, Szajna E, Shipley C, Arif AM, Mitchell MH, Halfen JA, Berreau LM. First Row Divalent Transition Metal Complexes of Aryl-Appended Tris((pyridyl)methyl)amine Ligands: Syntheses, Structures, Electrochemistry, and Hydroxamate Binding Properties. Inorg Chem 2003; 42:7472-88. [PMID: 14606843 DOI: 10.1021/ic034810y] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Divalent manganese, cobalt, nickel, and zinc complexes of 6-Ph(2)TPA (N,N-bis((6-phenyl-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine; [(6-Ph(2)TPA)Mn(CH(3)OH)(3)](ClO(4))(2) (1), [(6-Ph(2)TPA)Co(CH(3)CN)](ClO(4))(2) (2), [(6-Ph(2)TPA)Ni(CH(3)CN)(CH(3)OH)](ClO(4))(2) (3), [(6-Ph(2)TPA)Zn(CH(3)CN)](ClO(4))(2) (4)) and 6-(Me(2)Ph)(2)TPA (N,N-bis((6-(3,5-dimethyl)phenyl-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine; [(6-(Me(2)Ph)(2)TPA)Ni(CH(3)CN)(2)](ClO(4))(2) (5) and [(6-(Me(2)Ph)(2)TPA)Zn(CH(3)CN)](ClO(4))(2) (6)) have been prepared and characterized. X-ray crystallographic characterization of 1A.CH(3)()OH and 1B.2CH(3)()OH (differing solvates of 1), 2.2CH(3)()CN, 3.CH(3)()OH, 4.2CH(3)()CN, and 6.2.5CH(3)()CN revealed mononuclear cations with one to three coordinated solvent molecules. In 1A.CH(3)()OH and 1B.2CH(3)()OH, one phenyl-substituted pyridyl arm is not coordinated and forms a secondary hydrogen-bonding interaction with a manganese bound methanol molecule. In 2.2CH(3)()CN, 3.CH(3)()OH, 4.2CH(3)()CN, and 6.2.5CH(3)()CN, all pyridyl donors of the 6-Ph(2)TPA and 6-(Me(2)Ph)(2)TPA ligands are coordinated to the divalent metal center. In the cobalt, nickel, and zinc derivatives, CH/pi interactions are found between a bound acetonitrile molecule and the aryl appendages of the 6-Ph(2)TPA and 6-(Me(2)Ph)(2)TPA ligands. (1)H NMR spectra of 4 and 6 in CD(3)NO(2) solution indicate the presence of CH/pi interactions, as an upfield-shifted methyl resonance for a bound acetonitrile molecule is present. Examination of the cyclic voltammetry of 1-3 and 5 revealed no oxidative (M(II)/M(III)) couples. Admixture of equimolar amounts of 6-Ph(2)TPA, M(ClO(4))(2).6H(2)O, and Me(4)NOH.5H(2)O, followed by the addition of an equimolar amount of acetohydroxamic acid, yielded the acetohydroxamate complexes [((6-Ph(2)TPA)Mn)(2)(micro-ONHC(O)CH(3))(2)](ClO(4))(2) (8), [(6-Ph(2)TPA)Co(ONHC(O)CH(3))](ClO(4))(2) (9), [(6-Ph(2)TPA)Ni(ONHC(O)CH(3))](ClO(4))(2) (10), and [(6-Ph(2)TPA)Zn(ONHC(O)CH(3))](ClO(4))(2) (11), all of which were characterized by X-ray crystallography. The Mn(II) complex 8.0.75CH(3)()CN.0.75Et(2)()O exhibits a dinuclear structure with bridging hydroxamate ligands, whereas the Co(II), Ni(II), and Zn(II) derivatives all exhibit mononuclear six-coordinate structures with a chelating hydroxamate ligand.
Collapse
|
25
|
Robertson NJ, Carney MJ, Halfen JA. Chromium(II) and Chromium(III) Complexes Supported by Tris(2-pyridylmethyl)amine: Synthesis, Structures, and Reactivity. Inorg Chem 2003; 42:6876-85. [PMID: 14552639 DOI: 10.1021/ic034530i] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This report describes the synthesis, structural characterization, and polymerization behavior of a series of chromium(II) and chromium(III) complexes ligated by tris(2-pyridylmethyl)amine (TPA), including chromium(III) organometallic derivatives. For instance, the combination of TPA with CrCl(2) yields monomeric (TPA)CrCl(2) (1). A similar reaction of CrCl(2) with TPA, followed by chloride abstraction with NaBPh(4) or NaBAr(F)(4) (Ar(F) = 3,5-(CF(3))(2)C(6)H(3)), provides the weakly associated cationic dimers [(TPA)CrCl](2)[BPh(4)](2) (2A) and [(TPA)CrCl](2)[BAr(F)(4)](2) (2B), respectively. X-ray crystallographic analysis reveals that each chromium(II) center in 1, 2A, and 2B is a tetragonally elongated octahedron; such Jahn-Teller distortions are consistent with the observed high spin (S = 2) electronic configurations for these chromium(II) complexes. Likewise, reaction of CrCl(3)(THF)(3) with TPA, followed by anion metathesis with NaBPh(4) or NaBAr(F)(4), yields the monomeric, cationic chromium(III) complexes [(TPA)CrCl(2)][BPh(4)] (4A) and [(TPA)CrCl(2)][BAr(F)(4)] (4B), respectively. Treatment of 4A with methyl and phenyl Grignard reagents produces the cationic chromium(III) organometallic derivatives [(TPA)Cr(CH(3))(2)][BPh(4)] (5) and [(TPA)CrPh(2)][BPh(4)] (6), respectively. Similar reactions of 4A with organolithium reagents leads to intractable solids, presumably due to overreduction of the chromium(III) center. X-ray crystallographic analysis of 4A, 5, and 6 confirms that each possesses a largely undistorted octahedral chromium center, consistent with the observed S = (3)/(2) electronic ground states. Compounds 1, 2A, 2B, 4A, 4B, 5, and 6 are all active polymerization catalysts in the presence of methylalumoxane, producing low to moderate molecular weight high-density polyethylene.
Collapse
Affiliation(s)
- Nicholas J Robertson
- Department of Chemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin 54702, USA
| | | | | |
Collapse
|
26
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- Jason A Halfen
- Department of Chemistry, University of Wisconsin-Eau Claire, Eau Claire, WI 54702, USA.
| | | |
Collapse
|
27
|
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.
Collapse
Affiliation(s)
- Jason A Halfen
- Department of Chemistry, University of Wisconsin-Eau Claire, 105 Garfield Avenue, Eau Claire, WI 54702, USA.
| | | | | |
Collapse
|
28
|
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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
29
|
|
30
|
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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
31
|
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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
32
|
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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
33
|
|
34
|
|
35
|
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] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- J A Halfen
- Department of Chemistry, University of Wisconsin-Eau Claire, Eau Claire, Wisconsin 54702, USA
| | | | | | | |
Collapse
|
36
|
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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
37
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- D A Krogstad
- Department of Chemistry, University of the South, Sewanee, Tennessee 37375, USA
| | | | | | | |
Collapse
|
38
|
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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
|
39
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- J A Halfen
- Department of Chemistry, University of Wisconsin-Eau Claire, 105 Garfield Avenue, Eau Claire, Wisconsin 54701, USA.
| | | | | | | | | |
Collapse
|
40
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
Affiliation(s)
- B M Lam
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
41
|
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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
42
|
Affiliation(s)
- Jason A. Halfen
- Department of Chemistry, The University of WisconsinEau Claire, Eau Claire, Wisconsin 54702
| | - Jason K. Hallman
- Department of Chemistry, The University of WisconsinEau Claire, Eau Claire, Wisconsin 54702
| | - John A. Schultz
- Department of Chemistry, The University of WisconsinEau Claire, Eau Claire, Wisconsin 54702
| | - Joseph P. Emerson
- Department of Chemistry, The University of WisconsinEau Claire, Eau Claire, Wisconsin 54702
| |
Collapse
|
43
|
|
44
|
|
45
|
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] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jason A. Halfen
- Department of Chemistry, The University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055
| | | | | |
Collapse
|
46
|
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] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jason A. Halfen
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| | | | | |
Collapse
|
47
|
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] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Michael C. Keyes
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| | - Bradley M. Chamberlain
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| | - Scott A. Caltagirone
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| | - Jason A. Halfen
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| | - William B. Tolman
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| |
Collapse
|
48
|
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] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Lisa M. Berreau
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| | - Jason A. Halfen
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| | - Victor G. Young
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| | - William B. Tolman
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455
| |
Collapse
|
49
|
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] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
50
|
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] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Samiran Mahapatra
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, and Institut für Anorganische Chemie, University of Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland
| | - Susan Kaderli
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, and Institut für Anorganische Chemie, University of Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland
| | - Antoni Llobet
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, and Institut für Anorganische Chemie, University of Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland
| | - Yorck-Michael Neuhold
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, and Institut für Anorganische Chemie, University of Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland
| | - Tania Palanché
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, and Institut für Anorganische Chemie, University of Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland
| | - Jason A. Halfen
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, and Institut für Anorganische Chemie, University of Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland
| | - Victor G. Young,
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, and Institut für Anorganische Chemie, University of Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland
| | - Thomas A. Kaden
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, and Institut für Anorganische Chemie, University of Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland
| | - Lawrence Que,
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, and Institut für Anorganische Chemie, University of Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland
| | - Andreas D. Zuberbühler
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, and Institut für Anorganische Chemie, University of Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland
| | - William B. Tolman
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, and Institut für Anorganische Chemie, University of Basel, Spitalstrasse 51, CH-4056 Basel, Switzerland
| |
Collapse
|