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Affiliation(s)
- Charles G. Young
- Department of Chemistry and PhysicsLa Trobe Institute for Molecular ScienceLa Trobe University3086MelbourneVictoriaAustralia
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2
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Paul T, Rodehutskors PM, Schmidt J, Burzlaff N. Oxygen Atom Transfer Catalysis with Homogenous and Polymer-Supported N,N- and N,N,O-Heteroscorpionate Dioxidomolybdenum(VI) Complexes. Eur J Inorg Chem 2016. [DOI: 10.1002/ejic.201600026] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Tobias Paul
- Inorganic Chemistry; Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM); University of Erlangen-Nürnberg; Egerlandstr. 1 91058 Erlangen Germany
| | - Philipp M. Rodehutskors
- Inorganic Chemistry; Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM); University of Erlangen-Nürnberg; Egerlandstr. 1 91058 Erlangen Germany
| | - Jochen Schmidt
- Inorganic Chemistry; Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM); University of Erlangen-Nürnberg; Egerlandstr. 1 91058 Erlangen Germany
| | - Nicolai Burzlaff
- Inorganic Chemistry; Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM); University of Erlangen-Nürnberg; Egerlandstr. 1 91058 Erlangen Germany
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3
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Pimkov IV, Serli-Mitasev B, Peterson AA, Ratvasky SC, Hammann B, Basu P. Designing the Molybdopterin Core through Regioselective Coupling of Building Blocks. Chemistry 2015; 21:17057-72. [DOI: 10.1002/chem.201502845] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Indexed: 01/08/2023]
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4
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Heinze K. Bioinspired functional analogs of the active site of molybdenum enzymes: Intermediates and mechanisms. Coord Chem Rev 2015. [DOI: 10.1016/j.ccr.2015.04.010] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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5
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Majumdar A. Structural and functional models in molybdenum and tungsten bioinorganic chemistry: description of selected model complexes, present scenario and possible future scopes. Dalton Trans 2015; 43:8990-9003. [PMID: 24798698 DOI: 10.1039/c4dt00631c] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A brief description about some selected model complexes in molybdenum and tungsten bioinorganic chemistry is provided. The synthetic strategies involved and their limitations are discussed. Current status of molybdenum and tungsten bioinorganic modeling chemistry is presented briefly and synthetic problems associated therein are analyzed. Possible future directions which may expand the scope of modeling chemistry are suggested.
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Affiliation(s)
- Amit Majumdar
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India.
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6
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Sparacino-Watkins C, Stolz JF, Basu P. Nitrate and periplasmic nitrate reductases. Chem Soc Rev 2014; 43:676-706. [PMID: 24141308 DOI: 10.1039/c3cs60249d] [Citation(s) in RCA: 186] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The nitrate anion is a simple, abundant and relatively stable species, yet plays a significant role in global cycling of nitrogen, global climate change, and human health. Although it has been known for quite some time that nitrate is an important species environmentally, recent studies have identified potential medical applications. In this respect the nitrate anion remains an enigmatic species that promises to offer exciting science in years to come. Many bacteria readily reduce nitrate to nitrite via nitrate reductases. Classified into three distinct types--periplasmic nitrate reductase (Nap), respiratory nitrate reductase (Nar) and assimilatory nitrate reductase (Nas), they are defined by their cellular location, operon organization and active site structure. Of these, Nap proteins are the focus of this review. Despite similarities in the catalytic and spectroscopic properties Nap from different Proteobacteria are phylogenetically distinct. This review has two major sections: in the first section, nitrate in the nitrogen cycle and human health, taxonomy of nitrate reductases, assimilatory and dissimilatory nitrate reduction, cellular locations of nitrate reductases, structural and redox chemistry are discussed. The second section focuses on the features of periplasmic nitrate reductase where the catalytic subunit of the Nap and its kinetic properties, auxiliary Nap proteins, operon structure and phylogenetic relationships are discussed.
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7
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van Stipdonk MJ, Basu P, Dille SA, Gibson JK, Berden G, Oomens J. Infrared multiple photon dissociation spectroscopy of a gas-phase oxo-molybdenum complex with 1,2-dithiolene ligands. J Phys Chem A 2014; 118:5407-18. [PMID: 24988369 PMCID: PMC4338922 DOI: 10.1021/jp503222v] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
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Electrospray
ionization (ESI) in the negative ion mode was used
to create anionic, gas-phase oxo-molybdenum complexes with dithiolene
ligands. By varying ESI and ion transfer conditions, both doubly and
singly charged forms of the complex, with identical formulas, could
be observed. Collision-induced dissociation (CID) of the dianion generated
exclusively the monoanion, while fragmentation of the monoanion involved
decomposition of the dithiolene ligands. The intrinsic structure of
the monoanion and the dianion were determined by using wavelength-selective
infrared multiple-photon dissociation (IRMPD) spectroscopy and density
functional theory calculations. The IRMPD spectrum for the dianion
exhibits absorptions that can be assigned to (ligand) C=C,
C–S, C—C≡N, and Mo=O stretches. Comparison
of the IRMPD spectrum to spectra predicted for various possible conformations
allows assignment of a pseudo square pyramidal structure with C2v symmetry, equatorial coordination
of MoO2+ by the S atoms of the dithiolene ligands, and
a singlet spin state. A single absorption was observed for the oxidized
complex. When the same scaling factor employed for the dianion is
used for the oxidized version, theoretical spectra suggest that the
absorption is the Mo=O stretch for a distorted square pyramidal
structure and doublet spin state. A predicted change in conformation
upon oxidation of the dianion is consistent with a proposed bonding
scheme for the bent-metallocene dithiolene compounds [Lauher, J. W.; Hoffmann, R. 1976, 98, 1729−1742], where a large
folding of the dithiolene moiety along the S···S vector
is dependent on the occupancy of the in-plane metal d-orbital.
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Affiliation(s)
- Michael J van Stipdonk
- Department of Chemistry and Biochemistry, Duquesne University , 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
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8
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Affiliation(s)
- Russ Hille
- Department of Biochemistry, University of California, Riverside, Riverside, California 92521, United States
| | - James Hall
- Department of Biochemistry, University of California, Riverside, Riverside, California 92521, United States
| | - Partha Basu
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282, United States
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9
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Basu P, Kail BW, Adams AK, Nemykin VN. Quantitation of the ligand effect in oxo-transfer reactions of dioxo-Mo(VI) trispyrazolyl borate complexes. Dalton Trans 2012; 42:3071-81. [PMID: 23212540 DOI: 10.1039/c2dt32349d] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The oxygen atom transfer reactivity (OAT) of dioxo-Mo(VI) complexes of hydrotrispyrazolyl borate (hydrotris(3,5-dimethylpyrazolyl)borate, Tp(Me2); hydrotris(3-isopropylpyrazol-1-yl)borate, Tp(iPr)) with tertiary phosphines (PMe(3), PMe(2)Ph, PEt(3), PEt(2)Ph, PBu(n)(3), PMePh(2), or PEtPh(2)) has been investigated. In acetonitrile, these reactions proceed via the formation of a phosphoryl intermediate complex that undergoes a solvolysis reaction. We report the synthesis and characterization of several phosphoryl complexes. The rates of formation of phosphoryl complexes and their solvation were determined by spectrophotometry. The rates of the reactions and the properties of the phosphoryl species were investigated using the Quantitative Analysis of Ligand Effect (QALE) methodology. The results show that, at least in this system, the first step of the reaction is controlled primarily by the steric factor, and in the second step, both electronic and steric factors are important. We also analyzed the effect of ligands on the reaction rate i.e., Tp(Me2)vs. Tp(iPr).
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Affiliation(s)
- Partha Basu
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, PA 15228, USA.
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10
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Volpe M, Mösch-Zanetti NC. Molybdenum(VI) Dioxo and Oxo-Imido Complexes of Fluorinated β-Ketiminato Ligands and Their Use in OAT Reactions. Inorg Chem 2012; 51:1440-9. [DOI: 10.1021/ic201681u] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Manuel Volpe
- Institut für Chemie, Bereich Anorganische
Chemie, Karl-Franzens-Universität, Graz Stremayrgasse
16, A-8010 Graz, Austria
| | - Nadia C. Mösch-Zanetti
- Institut für Chemie, Bereich Anorganische
Chemie, Karl-Franzens-Universität, Graz Stremayrgasse
16, A-8010 Graz, Austria
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11
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Affiliation(s)
- Carola Schulzke
- School of Chemistry, Trinity College Dublin, Dublin 2, Ireland
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12
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Sugimoto H, Tano H, Miyake H, Itoh S. Generation of bis(dithiolene)dioxomolybdenum(vi) complexes from bis(dithiolene)monooxomolybdenum(iv) complexes by proton-coupled electron transfer in aqueous media. Dalton Trans 2011; 40:2358-65. [DOI: 10.1039/c0dt00763c] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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13
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Perera E, Basu P. Synthesis, characterization and structure of a low coordinate desoxomolybdenum cluster stabilized by a dithione ligand. Dalton Trans 2009:5023-8. [PMID: 19662295 PMCID: PMC2894468 DOI: 10.1039/b904113c] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Using an oxidized state of a dithiolene ligand, diisopropylpiperazine-2,3-dithione (i-Pr(2)Pipdt), two monooxo-molybdenum complexes have been synthesized. From one of them, a desoxomolybdenum cluster, [(i-Pr(2)Pipdt)Mo](4)[BF(4)](4) has been prepared. The molecular structure of this cluster reveals metal-metal interactions and weak coordination by the BF(4) anion.
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Affiliation(s)
- Eranda Perera
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, PA 15282, USA
| | - Partha Basu
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, PA 15282, USA
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14
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Basu P, Nemykin VN, Sengar RS. Substituent Effect on Oxygen Atom Transfer Reactivity from Oxomolybdenum Centers: Synthesis, Structure, Electrochemistry, and Mechanism. Inorg Chem 2009; 48:6303-13. [DOI: 10.1021/ic900579s] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Partha Basu
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282
| | - Victor N. Nemykin
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282
| | - Raghvendra S. Sengar
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282
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15
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Sugimoto H, Tsukube H. Chemical analogues relevant to molybdenum and tungsten enzyme reaction centres toward structural dynamics and reaction diversity. Chem Soc Rev 2008; 37:2609-19. [PMID: 19020675 DOI: 10.1039/b610235m] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Recent characterisation of molybdenum and tungsten enzymes revealed novel structural types of reaction centres, as well as providing new subjects of interest as synthetic chemical analogues. This tutorial review highlights the structure/reactivity relationships of the enzyme reaction centres and chemical analogues. Chemical analogues for the oxygen atom transfer enzymes have been well expanded in structure and reactivity. Other types of chemical analogues that exhibit different coordination chemistry have recently been presented for reaction centres of the hydroxylation and dehydrogenation enzymes and others.
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Affiliation(s)
- Hideki Sugimoto
- Department of Chemistry, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, 558-8585, Japan.
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16
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Studies on a new dinuclear CoII–pterin complex exhibiting reactivity towards phenylalanine and bromobenzene. TRANSIT METAL CHEM 2007. [DOI: 10.1007/s11243-007-0237-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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17
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Tran BL, Carrano CJ. Oxo−Molybdenum(VI,V,IV) Complexes of the Facially Coordinating Tris(mercaptoimidazolyl)borate Ligand: Synthesis, Characterization, and Oxygen Atom Transfer Reactivity. Inorg Chem 2007; 46:5429-38. [PMID: 17521186 DOI: 10.1021/ic7005259] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A series of monooxo-Mo(IV,V) and dioxo-Mo(VI) complexes of the "soft" tripodal ligand, sodium tris(mercaptoimidazolyl)borate (NaTm(Me)), have been synthesized as potential oxygen atom transfer (OAT) models for sulfite oxidase. Complexes have been characterized by X-ray crystallography, cyclic voltammetry, and EPR, where appropriate. Oxygen atom transfer kinetics of Tm(Me)MoO(2)Cl, both stoichiometric and catalytic, have been studied by a combination of UV-vis and (31)P NMR spectroscopies under a variety of conditions. OAT rates are consistent with previously established relationships between redox potential/reactivity and mechanistic studies. The analysis of these complexes as potential structural and functional analogues of relevance to molybdoenzymes is further discussed.
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Affiliation(s)
- Ba L Tran
- Department of Chemistry and Biochemistry, San Diego State University, San Diego, California 92182-1030, USA
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18
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Tran BL, Carrano CJ. Synthesis and characterization of heteroscorpionate dioxo-tungsten(VI) complexes. Inorganica Chim Acta 2007. [DOI: 10.1016/j.ica.2006.10.024] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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19
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Sugimoto H, Tarumizu M, Miyake H, Tsukube H. Bis(dithiolene) Molybdenum Complex that Promotes Combined Coupled Electron–Proton Transfer and Oxygen Atom Transfer Reactions: A Water-Active Model of the Arsenite Oxidase Molybdenum Center. Eur J Inorg Chem 2006. [DOI: 10.1002/ejic.200600785] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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20
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Kail BW, Pérez LM, Zarić SD, Millar AJ, Young CG, Hall MB, Basu P. Mechanistic Investigation of the Oxygen-Atom-Transfer Reactivity of Dioxo-molybdenum(VI) Complexes. Chemistry 2006; 12:7501-9. [PMID: 16865754 DOI: 10.1002/chem.200600269] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The oxygen-atom-transfer (OAT) reactivity of [LiPrMoO2(OPh)] (1, LiPr=hydrotris(3-isopropylpyrazol-1-yl)borate) with the tertiary phosphines PEt3 and PPh2Me in acetonitrile was investigated. The first step, [LiPrMoO2(OPh)]+PR3-->[LiPrMoO(OPh)(OPR3)], follows a second-order rate law with an associative transition state (PEt3, DeltaH not equal=48.4 (+/-1.9) kJ mol-1, DeltaS not equal=-149.2 (+/-6.4) J mol-1 K-1, DeltaG not equal=92.9 kJ mol-1; PPh2Me, DeltaH not equal=73.4 (+/-3.7) kJ mol-1, DeltaS not equal=-71.9 (+/-2.3) J mol-1 K-1, DeltaG not equal=94.8 kJ mol-1). With PMe3 as a model substrate, the geometry and the free energy of the transition state (TS) for the formation of the phosphine oxide-coordinated intermediate were calculated. The latter, 95 kJ mol-1, is in good agreement with the experimental values. An unexpectedly large O-P-C angle calculated for the TS suggests that there is significant O-nucleophilic attack on the P--C sigma* in addition to the expected nucleophilic attack of the P on the Mo==O pi*. The second step of the reaction, that is, the exchange of the coordinated phosphine oxide with acetonitrile, [LiPrMoO(OPh)(OPR3)]+MeCN-->[LiPrMoO(OPh)(MeCN)]+OPR3, follows a first-order rate law in MeCN. A dissociative interchange (Id) mechanism, with activation parameters of DeltaH not equal=93.5 (+/-0.9) kJ mol-1, DeltaS not equal=18.2 (+/-3.3) J mol-1 K-1, DeltaG not equal=88.1 kJ mol-1 and DeltaH not equal=97.9 (+/-3.4) kJ mol-1, DeltaS not equal=47.3 (+/-11.8) J mol-1 K-1, DeltaG not equal=83.8 kJ mol-1, for [LiPrMoO(OPh)(OPEt3)] (2 a) and [LiPrMoO(OPh)(OPPh2Me)] (2 b), respectively, is consistent with the experimental data. Although gas-phase calculations indicate that the Mo--OPMe3 bond is stronger than the Mo--NCMe bond, solvation provides the driving force for the release of the phosphine oxide and formation of [LiPrMoO(OPh)(MeCN)] (3).
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Affiliation(s)
- Brian W Kail
- Department of Chemistry and Biochemistry, Duquesne University, Mellon Hall, Pittsburgh, PA 15282, USA
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21
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Cervilla A, Pérez-Pla F, Llopis E, Piles M. Unusual Oxidation of Phosphines Employing Water as the Oxygen Atom Source and Tris(benzene-1,2-dithiolate)molybdenum(VI) as the Oxidant. A Functional Molybdenum Hydroxylase Analogue System. Inorg Chem 2006; 45:7357-66. [PMID: 16933938 DOI: 10.1021/ic052161f] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The kinetics of the reaction of Mo(VI)(S2C6H4)3 with organic phosphines to produce the anionic Mo(V) complex, Mo(V)(S2C6H4)3-, and phosphine oxide have been investigated. Reaction rates, monitored by UV-vis stopped-flow spectrophotometry, were studied in THF/H2O media as a function of the concentration of phosphine, molybdenum complex, pH, and water concentration. The reaction exhibits pH-dependent phosphine saturation kinetics and is first-order in complex concentration. The water concentration strongly enhances the reaction rate, which is consistent with the formation of Mo(VI)(S2C6H4)3(H2O) adduct as a crucial intermediate. The observed pH dependence of the reaction rate would arise from the distribution between acid and basic forms of this adduct. Apparently, the electrophilic attack by the phosphine at the oxygen requires the coordinated water to be in the unprotonated hydroxide form, Mo(VI)(S2C6H4)3(HO)-. This is followed by the concerted abstraction of 2e-, H+ by the Mo(VI) center to give Mo(IV)(S2C6H4)3(2-), H+, and the corresponding phosphine oxide. However, this Mo(IV) complex product is oxidized rapidly to Mo(V)(S2C6H4)3- via comproportionation with unreacted Mo(VI)(S2C6H4)3. The Mo(V) complex thus formed can be oxidized to the starting Mo(VI) complex upon admission of O2. Consequently, Mo(VI)(S2C6H4)3 is a catalyst for the autoxidation of phosphines in the presence of water. Additionally, there was a detectable variation in the reactivity for a series of tertiary phosphines. The rate of Mo(VI) complex reduction increases as does the phosphine basicity: (p-CH3C6H4)3P > (C6H5)3P > (p-ClC6H4)3P. Oxygen isotope tracing confirms that water rather than dioxygen is the source of the oxygen atom which is transferred to the phosphine. Such reactivity parallels oxidase activity of xanthine enzyme with phosphine as oxygen atom acceptor and Mo(VI)(S2C6H4)3 as electron acceptor.
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Affiliation(s)
- Antonio Cervilla
- ICMUV, P.O. Box 2085, Polígono La Coma, Paterna, Valencia, Spain.
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22
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Hoffman JT, Tran BL, Carrano CJ. Oxidation-state and metal-ion dependent stereoisomerization in oxo molybdenum and tungsten complexes of a bulky alkoxy heteroscorpionate ligand. Dalton Trans 2006:3822-30. [PMID: 16883409 DOI: 10.1039/b604751c] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Monooxo Mo(V) complexes of a N2O heteroscorpionate ligand designated (L10O) are found to exist as isolable cis and trans isomers. We have been able to trap the kinetically labile cis isomer and follow its isomerization to the thermodynamically more stable trans form. We have also followed the kinetics of isomerization between the cis and trans isomers of the corresponding dioxo Mo(VI) and W(VI) species. Here the trans is the labile isomer that spontaneously converts to the thermodynamically more stable cis. It is observed that at 60 degrees C in DMSO the Mo(VI) complex isomerizes approximately 6.5 times faster than the Mo(V) and nearly 5 times faster than the corresponding W(VI) analogs. The temperature dependence to the kinetics of the Mo(V) and Mo(VI) isomerizations give activation parameters that are similar for both oxidation states and consistent with those previously observed in [(L1O)MoOCl2] suggesting a similar twist mechanism is operating in all cases. Thus there are oxidation state, metal ion and donor atom dependent differences in isomeric stability that could have significant implications for understanding the mechanisms of both enzymatic and nonenzymatic oxo atom transfer reactions catalyzed by complexes of Mo, W and Re.
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Affiliation(s)
- Justin T Hoffman
- Department of Chemistry and Biochemistry, San Diego State University, San Diego, CA 82182-1030, USA
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23
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Doonan CJ, Millar AJ, Nielsen DJ, Young CG. cis-Dioxomolybdenum(VI) and oxo(phosphine oxide)molybdenum(IV) complexes: steric and electronic fine-tuning of cis-[MoOS]2+ precursors. Inorg Chem 2005; 44:4506-14. [PMID: 15962957 DOI: 10.1021/ic050052v] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The complexes cis-Tp(iPr)Mo(VI)O2(OAr) (Tp(iPr) = hydrotris(3-isopropylpyrazol-1-yl)borate, -OAr = phenolate or naphtholate derivative) are formed upon metathesis of Tp(iPr)MoO2Cl and HOAr/NEt3 in dichloromethane. The orange, diamagnetic dioxo-Mo(VI) complexes exhibit strong nu(MoO2) IR bands at ca. 930 and 905 cm(-1) and NMR spectra indicative of C(s) symmetry. They undergo electrochemically reversible, one-electron reductions at potentials in the range -0.714 to -0.855 V vs SCE (in MeCN) and react with PEt3 to produce Tp(iPr)Mo(IV)O(OAr)(OPEt3). The green, diamagnetic oxo-Mo(IV) complexes display a single nu(MoO) IR band at ca. 950 cm(-1) and exhibit NMR spectra indicative of C1 symmetry. The crystal structures of eight dioxo-Mo(VI) complexes have been determined to assess the degree of frontal (O3-donor face) steric congestion at the Mo center, to identify complexes amenable to conversion into monomeric oxosulfido-Mo(VI) derivatives. The complexes display distorted octahedral geometries, with a cis arrangement of terminal oxo ligands, with d(Mo=O)av = 1.694 A and angle(MoO2)av = 103.4 degrees. Maximal frontal steric congestion is observed in the 2-phenolate derivatives, and these are identified as precursors for strictly monomeric(solid and solution state) oxosulfido-Mo(VI) counterparts.
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Hanna TA, Ghosh AK, Ibarra C, Zakharov LN, Rheingold AL, Watson WH. Facile Formation of Molybdenum(VI) Monooxo Aryloxides MoO(OAr)4-nCln from Molybdenum Dioxo Dichloride. Inorg Chem 2004; 43:7567-9. [PMID: 15554614 DOI: 10.1021/ic048976q] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Molybdenum monooxo compoundsMoO(OAr)4-nCln (n=0-2, Ar=2,6-Me2C6H3 or 2,6-i-Pr2C6H3) have been synthesized starting from the dioxo precursor MoO2Cl2. The complexes are characterized spectroscopically and by X-ray diffraction. The formation mechanism likely involves phenol precoordination followed by addition across the Mo=O bond.
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Affiliation(s)
- Tracy A Hanna
- Department of Chemistry, Texas Christian University, Box 298860, Fort Worth, Texas 76129, USA.
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25
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Hoffman JT, Einwaechter S, Chohan BS, Basu P, Carrano CJ. Isomerization and Oxygen Atom Transfer Reactivity in Oxo−Mo Complexes of Relevance to Molybdoenzymes. Inorg Chem 2004; 43:7573-5. [PMID: 15554616 DOI: 10.1021/ic048775m] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Both dioxo Mo(VI) and mono-oxo Mo(V) complexes of a sterically restrictive N2O heteroscorpionate ligand are found to exist as cis and trans isomers. The thermodynamically stable isomer differs for the two oxidation states, but in each case, we have isolated the kinetically labile isomer and followed its isomerization to the thermodynamically stable form. The Mo(VI) complex is more stable in the cis geometry and isomerizes more than 6 times faster than the Mo(V) complex, which prefers the trans geometry. In OAT reactions with PPh3, the trans isomer of the dioxo-Mo(VI) reacts approximately 20 times faster than the cis isomer. Thus, there are both oxidation state and donor atom dependent differences in isomeric stability and reactivity that could have significant functional implications for molybdoenzymes such as DMSO reductase.
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Affiliation(s)
- Justin T Hoffman
- Department of Chemistry, San Diego State University, San Diego, California 92182-1030, USA
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Hammes BS, Chohan BS, Hoffman JT, Einwächter S, Carrano CJ. A Family of Dioxo−Molybdenum(VI) Complexes of N2X Heteroscorpionate Ligands of Relevance to Molybdoenzymes. Inorg Chem 2004; 43:7800-6. [PMID: 15554645 DOI: 10.1021/ic049130p] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Four new Mo(VI)-dioxo complexes of a family of N2X heteroscorpionate ligands are reported which, together with data already available for (TpR)-, provide a unique example of a comprehensive set of isostructural, isoelectronic complexes differing only in one biologically relevant donor atom. A study of these complexes allows for a direct comparison of structural, spectroscopic, and oxygen atom transfer reactivity properties of the Mo(VI)-dioxo center (of relevance to various families of molybdoenzymes) as a function of donor atom identity.
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Affiliation(s)
- Brian S Hammes
- Department of Chemistry and Biochemistry, San Diego State University, San Diego, California 92182-1030, USA
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Shan X, Ellern A, Guzei IA, Espenson JH. Ligand Displacement and Oxidation Reactions of Methyl(oxo)rhenium(V) Complexes. Inorg Chem 2004; 43:3854-62. [PMID: 15206866 DOI: 10.1021/ic049772c] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Compounds that contain the anion [MeReO(edt)(SPh)](-) (3-) were synthesized with the countercations 2-picolinium (PicH+3-) and 2,6-lutidinium (LutH+3-), where edt is 1,2-ethanedithiolate. Both PicH+3- and MeReO(edt)(tetramethylthiourea) (4) were crystallographically characterized. The rhenium atom in each of these compounds exists in a five-coordinate distorted square pyramid. In the solid state, PicH+3- contains an anion with a short (d(SH) = 232 pm) and nearly linear hydrogen-bonded (N-H.S) interaction to the cation. Ligand substitution reactions were studied in chloroform. Displacement of PhSH by PPh(3) follows second-order kinetics, d[MeReO(edt)(PPh(3))]/dt = k[PicH+3-][PPh3], whereas with pyridines an unusual form was found, d[MeReO(edt)(Py)]/dt = k[PyH+3-][Py](2), in which the conversion of PicH+3- to PyH+3- has been incorporated. Further, added Py accelerates the formation of [MeReO(edt)(PPh3)], v = k.[PicH+3-].[PPh3].[Py]. Compound 4, on the other hand, reacts with both PPh(3) and pyridines, L, at a rate given by d[MeReO(edt)(L)]/dt = k.[4].[L]. When PicH+3- reacts with pyridine N-oxides, a three-stage reaction was observed, consistent with ligand replacement of SPh(-) by PyO, N-O bond cleavage of the PyO assisted by another PyO, and eventual decomposition of MeRe(O)(edt)(OPy) to MeReO(3). Each of first two steps showed a large substituent effect; Hammett analysis gave rho(1) = -5.3 and rho(2) = -4.3.
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Affiliation(s)
- Xiaopeng Shan
- Ames Laboratory and Department of Chemistry, Iowa State University, Ames, IA 50011, USA
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Enemark JH, Cooney JJA, Wang JJ, Holm RH. Synthetic Analogues and Reaction Systems Relevant to the Molybdenum and Tungsten Oxotransferases. Chem Rev 2003; 104:1175-200. [PMID: 14871153 DOI: 10.1021/cr020609d] [Citation(s) in RCA: 424] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- John H Enemark
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA
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Carrano CJ, Chohan BS, Hammes BS, Kail BW, Nemykin VN, Basu P. Donor atom dependent geometric isomers in mononuclear oxo-molybdenum(V) complexes: implications for coordinated endogenous ligation in molybdoenzymes. Inorg Chem 2003; 42:5999-6007. [PMID: 12971770 DOI: 10.1021/ic0262785] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have previously demonstrated that the complex [(L1O)MoOCl(2)], where L1OH = (2-hydroxy-3-tert-butyl-5-methylphenyl)bis(3,5-dimethylpyrazolyl)methane, exists as both cis and trans isomers (Kail, B.; Nemykin, V. N.; Davie, S. R.; Carrano, C. J.; Hammes, B. S.; Basu, P. Inorg. Chem. 2002, 41, 1281-1291). Here, the cis isomer is defined as the geometry with the heteroatom in the equatorial position, and the trans isomer is designated as the geometry with the heteroatom positioned trans to the terminal oxo group. The trans isomer represents the thermodynamically more stable geometry as indicated by its spontaneous formation from the cis isomer. In this report, we show that for complexes of [(LO)MoOCl(2)], where LOH is the sterically less restrictive (2-hydroxyphenyl)bis(3,5-dimethylpyrazolyl)methane, only the trans isomer could be isolated, while in the corresponding thiolate containing ligand (2-dimethylethanethiol)bis(3,5-dimethylpyrazolyl)methane (L3SH) only the cis isomer could be observed. In addition, we have isolated and structurally characterized the complex [(L1O)MoO(OPh)(Cl)], a rare example of a species possessing both cis and trans phenolates. Using DFT calculations, we have investigated the origins of the differences in stability between the cis and trans isomers in these complexes and suggest that they are related to the trans influence of the oxo-group. Crystal data for [(LO)MoOCl(2)] (1) include that it crystallizes in the triclinic space group P(-)1 with cell dimensions a = 8.9607 (12) A, b = 10.596 (4) A, c = 13.2998 (13) A, alpha = 98.03 (2) degrees, beta = 103.21 (2) degrees, gamma = 110.05(2) degrees, and Z = 2. [(L1O)MoO(OPh)Cl].2CH(2)Cl(2) (2.2CH(2)Cl(2)) crystallizes in the triclinic space group P(-)1 with cell dimensions a = 12.2740 (5) A, b = 13.0403 (5) A, c = 13.6141 (6) A, alpha = 65.799 (2) degrees, beta = 64.487 (2) degrees, gamma = 65.750 (2) degrees, and Z = 2. [(L3S)Mo(O)Cl(2)] (3) crystallizes in the orthorhombic space group Pna2(1), with cell dimensions a = 13.2213 (13) A, b = 8.817 (2) A, c = 15.649 (4) A, and Z = 4. The implications of these results on the function of mononuclear molybdoenzymes such as sulfite oxidase, and the DMSO reductase, are discussed.
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Affiliation(s)
- Carl J Carrano
- Department of Chemistry and Biochemistry, Southwest Texas State University, San Marcos, TX 78666, USA
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Kail B, Nemykin VN, Davie SR, Carrano CJ, Hammes B, Basu P. Synthesis, characterization, electrochemistry, electronic structure, and isomerization of mononuclear oxo-molybdenum(V) complexes: the serine gate hypothesis in the function of DMSO reductases. Inorg Chem 2002; 41:1281-91. [PMID: 11874366 DOI: 10.1021/ic011169w] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Crystal structures of DMSO reductases isolated from two different sources and the crystal structure of related trimethylamine-N-oxide reductase indicate that the angle between the terminal oxo atom on the molybdenum and the serinato oxygen varies significantly. To understand the significance of this angular variation, we have synthesized two isomeric compounds of the heteroscorpionato ligand (L1OH) (cis- and trans-(L1O)Mo(V)OCl(2)), where the phenolic oxygen mimics the serinato oxygen donor. Density functional and semiempirical calculations indicate that the trans isomer is more stable than the cis. The lower stability of the cis isomer can be attributed to two factors. First, a strong antibonding interaction between the phenolic oxygen with molybdenum d(xy) orbital raises the energy of this orbital. Second, the strong trans influence of the terminal oxo group in the trans isomer places the phenol ring, and hence the bulky tertiary butyl group, in a less sterically hindered position. In solution, the cis isomer spontaneously converts to the thermodynamically favorable trans isomer. This geometric transformation follows a first-order process, with an enthalpy of activation of 20 kcal/mol and an entropy of activation of -9 cal/mol K. Computational analysis at the semiempirical level supports a twist mechanism as the most favorable pathway for the geometric transformation. The twist mechanism is further supported by detailed mass spectral data collected in the presence of excess tetraalkylammonium salts. Both the cis and trans isomers exhibit well-defined one-electron couples due to the reduction of molybdenum(V) to molybdenum(IV), with the cis isomer being more difficult to reduce. Both isomers also exhibit oxidative couples because of the oxidation of molybdenum(V) to molybdenum(VI), with the cis isomer being easier to oxidize. This electrochemical behavior is consistent with a higher-energy redox orbital in the cis isomer, which has been observed computationally. Collectively, this investigation demonstrates that by changing the O(t)-Mo-O(p) angle, the reduction potential can be modulated. This geometrically controlled modulation may play a gating role in the electron-transfer process during the regeneration steps in the catalytic cycle.
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Affiliation(s)
- Brian Kail
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282, USA
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