Studies of the protonation and oxidation of sulfido ligands in dinuclear molybdenum complexes

Birnbaum, Jerome C.; Godziela, Gregory M.; Maciejewski, Mariusz; Tonker, T. L.; Haltiwanger, R. C.; Dubois, Maxime

doi:10.1021/om00116a015

Cited by 27 publications

(22 citation statements)

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“…However, it is unclear if the S center is a sufficiently strong hydride acceptor. In model complexes, the formation of MoSH groups appears to be dominated by protonation reactions, − and although [Cp* 2 Mo 2 S 4 ]-type complexes containing bridging sulfides have been tuned to be thermodynamically capable hydride donors or acceptors, their kinetic behavior has not been investigated. The mechanism in Figure A is consistent with the mechanism of catalysis by metal-independent FDHs, which demonstrate the possibility of a Mo-independent hydride-transfer reaction.…”

Section: Discussionmentioning

confidence: 99%

Oxidation-State-Dependent Binding Properties of the Active Site in a Mo-Containing Formate Dehydrogenase

et al. 2017

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Molybdenum-containing formate dehydrogenase H from Escherichia coli (EcFDH-H) is a powerful model system for studies of the reversible reduction of CO2 to formate. However, the mechanism of FDH catalysis is currently under debate, and whether the primary Mo coordination sphere remains saturated or one of the ligands dissociates to allow direct substrate binding during turnover is disputed. Herein, we describe how oxidation-state-dependent changes at the active site alter its inhibitor binding properties. Using protein film electrochemistry, we show that formate oxidation by EcFDH-H is inhibited strongly and competitively by N3–, OCN–, SCN–, NO2–, and NO3–, whereas CO2 reduction is inhibited only weakly and not competitively. During catalysis, the Mo center cycles between the formal Mo(VI)=S and Mo(IV)—SH states, and by modeling chronoamperometry data recorded at different potentials and substrate and inhibitor concentrations, we demonstrate that both formate oxidation and CO2 reduction are inhibited by selective inhibitor binding to the Mo(VI)=S state. The strong dependence of inhibitor-binding affinity on both Mo oxidation state and inhibitor electron-donor strength indicates that inhibitors (and substrates) bind directly to the Mo center. We propose that inhibitors bind to the Mo following dissociation of a selenocysteine ligand to create a vacant coordination site for catalysis and close by considering the implications of our data for the mechanisms of formate oxidation and CO2 reduction.

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Section: Discussionmentioning

confidence: 99%

Oxidation-State-Dependent Binding Properties of the Active Site in a Mo-Containing Formate Dehydrogenase

et al. 2017

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“…A second facile hydrogen addition reaction has been observed for the one-electron oxidation product of the Mo(IV)/(IV) methanedithiolate bridged complex, which exists as a dimer of dimers linked by a bond at the μ-sulfido ligands (Structure A, Cp' = MeCp) (33). Addition of hydrogen proceeds rapidly at room temperature to form the hydrosulfido cation, equation 4.…”

Section: Hs-mentioning

confidence: 99%

Syntheses, Structures, and Reactions of Cyclopentadienyl Metal Complexes with Bridging Sulfur Ligands

DuBois

Jagirdar

Noll

et al. 1996

ACS Symposium Series

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Homogeneous cyclopentadienyl complexes of molybdenum and rhenium that contain sulfido and/or disulfido ligands have been synthesized. The structures and reactivities of the complexes are compared, and reactions which are relevant to those of heterogeneous metal sulfide catalysts are discussed.An intriguing feature of the heterogeneous transition metal sufides is their ability to participate in organometallic chemistry by virtue of their reactivity with hydrogen and with organic substrates. The most prominent class of reactions catalyzed by metal sulfide surfaces is the commercially important hydrotreating process, in which the hydrogenolysis of C-S and C-N bonds in aromatic heterocycles is effected (1-8). While a molybdenum sufide based system is the catalyst used most widely in industry, other metal sulfides have been shown to be more active than the molybdenum system in this process (9). Additional reactions for metal sulfides have also been characterized, either as a part of the hydrotreating sequence or in independent studies (1,2). These include hydrogen activation and hydrogen/deuterium exchange, the hydrogénation and isomerization of olefins, and the dehydrogenation of alkanes. Reactions with carbon monoxide have been identified for molybdenum sulfide surfaces, including the reduction of CO to methane or to alcohols (10-13), and its conversion to C0 2 in the water gas shift reaction (14). Despite this extensive range of reactivity, examples of homogeneous metal complexes with sulfido ligands that react with dihydrogen and with organic molecules are still relatively rare (75). In this paper we focus on two of the metal sulfides, those of molybdenum and rhenium. We briefly compare characteristics of M0S2 and ReS 2 that contribute to their catalytic chemistry, and we describe molecular derivatives of molybdenum and rhenium that permit us to probe reactions related to those of the heterogeneous systems. Heterogeneous Molybdenum and Rhenium SulfidesBoth M0S2 and ReS 2 crystallize as layered sulfides, but there are significant 1

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“…In previous work we have shown that the one-electron oxidation of (Cp‘MoS) 2 S 2 CH 2 results in the formation of the diamagnetic tetranuclear dication 1 , which contains two dimers linked by a bond between bridging sulfido ligands (eq 1) . The sulfur−sulfur bond distance in 1 is relatively long (2.14 Å), and this appears to be a reactive electrophilic site in the molecule.…”

Section: Introductionmentioning

confidence: 96%

Electrophilic Substitution of Nitrogen Heterocycles by Molybdenum Sulfide Complexes

et al. 2000

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The electrophilic tetranuclear complex [(Cp′Mo(µ-S)) 2 (S 2 CH 2 )] 2 (BF 4 ) 2 (1: Cp′ ) C 5 H 5 (1a), C 5 H 4 Me (1b)), in which two dinuclear complexes are joined by a sulfur-sulfur bond, reacts with the electron-rich nitrogen heterocycles pyrroles and indoles at room temperature. The reactions involve heterolytic scission of the disulfide bond by the nucleophiles followed by proton transfer, and the products areThe reactions have been characterized for pyrrole, 1-methylpyrrole, 1,2,5-trimethylpyrrole, and 1-methylindole. The regiochemistry of the reactions depends on pyrrole substituents. Complex 1 also reacts readily with the coordinated pyrrolyl ligand in (PMe 2 Ph) 3 Cl 2 Re(NC 4 H 4 ). The electrophilic substitution occurs on the 3-position of the heterocycle to form [(Cp′Mo) 2 (S 2 CH 2 )(µ-S)(µ-SC 4 H 3 N)ReCl 2 (PMe 2 Ph) 3 ]BF 4 (7). Complex 7 undergoes a further reaction with 1 to give the hydrogen abstraction product [(Cp′Mo) 2 (S 2 CH 2 )(µ-S 2 C 4 H 2 N)ReCl 2 (PMe 2 Ph) 3 ]BF 4 ( 8). An X-ray diffraction study of 8b confirms that the 3-and 4-carbons of the pyrrolyl ligand are coordinated to the µ-sulfido ligands of the molybdenum dimer. The new products suggest that there are a number of ways in which electron-rich heterocycles might interact with a sulfided molybdenum catalyst in the hydrodenitrogenation reactions. Reactions of 1 with other nucleophiles have also been surveyed.

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Studies of the protonation and oxidation of sulfido ligands in dinuclear molybdenum complexes

Cited by 27 publications

References 0 publications

Oxidation-State-Dependent Binding Properties of the Active Site in a Mo-Containing Formate Dehydrogenase

Oxidation-State-Dependent Binding Properties of the Active Site in a Mo-Containing Formate Dehydrogenase

Syntheses, Structures, and Reactions of Cyclopentadienyl Metal Complexes with Bridging Sulfur Ligands

Electrophilic Substitution of Nitrogen Heterocycles by Molybdenum Sulfide Complexes

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