Chemical and electrochemical redox transformations of oxomolybdenum and oxotungsten tetrathiolate complexes

Soong, S.-L.; Chebolu, Venkat; Koch, Stephen A.; O'sullivan, T.; Millar, Michelle

doi:10.1021/ic00243a001

Cited by 29 publications

(20 citation statements)

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“…The Mo-oxo distance in 1 [1.684(8) ] is identical within error to other Mo V (O)S 4 complexes [39,40,41,42,43,44,45,46,47] and is typical for a terminal Mo=O [71]. Essentially the same metal-oxygen distances (1.6±1.8 ) have been found for the Mo(IV) and Mo(VI) oxo-containing enzyme sites by X-ray crystallography [18,21,22,23,24,25] and X-ray absorption spectroscopy [72,73,74 190.59 (13) The Mo ion in 1 sits 0.703 out of the S 4 basal plane, which is on the low end of those reported for other Mo V (O)S 4 structures (0.687±0.82 ) [39,41,42,43,44,45,46,47], as well as when compared to the crystallographically characterized Mo(IV) and Mo(VI) enzyme sites with two dithiolene groups (0.4±1.7 ) [20,21,23,24,26].…”

Section: Resultsmentioning

confidence: 57%

“…The addition of 2.5 equiv of H 2 L (as required by the reaction stoichiometry) results in a higher yield of 1, typically with isolation of 65±70% of 1. The synthesis of Mo(V) complexes from Mo(VI) precursors via thiol-induced reduction has been seen in other systems [40,45,52,53,54]. The Et 4 N + , PPh 4 + , and Bu 4 N + salts of [Mo(O)L 2 ] ± have also been prepared.…”

Section: Resultsmentioning

confidence: 95%

“…Thiolate-to-metal transitions are observed in other Mo(V)-oxo-tetrathiolate complexes from 436 to 729 nm [43,44,45,47,56,57,58,59,60,61,62]. The Mo(V) tetrathiolate complexes that give the highest energy bands have alkylthiolate or amide-substituted thiophenolate ligands; the lowest energy bands are seen for complexes with benzenedithiolate ligands.…”

Section: Resultsmentioning

confidence: 96%

“…Although this band occurs near the lower end of the 920±1050 cm ±1 range seen for Mo=O complexes [67], it is typical for Mo V (O)S 4 complexes, which absorb from 910 to 950 cm ±1 [42,43,44,45,46,47,56,57,58,59,60,61]. Resonance Raman (RR) data for this region of the relevant enzymes' Mo(V) states have not been reported, presumably owing to the difficulty in generating a Mo(V) enzyme free of significant Mo(IV) and Mo(VI) impurities.…”

Section: Resultsmentioning

confidence: 99%

“…Nearly all of the handful of crystallographically characterized Mo V (O)S 4 complexes [39,40,41,42,43,44,45,46,47] have ligands that direct their steric bulk primarily away from the metal center. Here we report the synthesis and characterization of a unique Mo(V) complex, with dithiolate ligands that incorporate a biphenyl framework which also provides some steric protection that may inhibit the undesirable dimer formation.…”

Section: Introductionmentioning

confidence: 99%

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A mononuclear molybdenum(V) mono-oxo biphenyl-2,2′-dithiolate complex in which the metal resides within a cleft formed by the ligands and that exhibits N-H...S hydrogen bonding in the solid state

Conry

Tipton

2001

J. Biol. Inorg. Chem.

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The reaction of Mo(O)2(acac)2, H2L (2,2'-dimercaptobiphenyl), and NEt3 produced the mononuclear Mo(V) complex Et3NH[Mo(O)(L)2] (1). Molybdenum mono-oxo tetrathiolate complexes such as 1 are studied as potential structural or functional models for pyranopterin-containing molybdoenzymes. Complex 1 has been crystallographically characterized. The solid-state structure reveals that the molybdenum ion sits within a cleft formed by the biphenyl backbone of the ligands, providing some steric protection. In addition, there is a hydrogen bond between the amine hydrogen of [Et3NH]+ and one of the thiolate sulfur atoms. A difference in solution reactivity between 1 and a derivative without a hydrogen-bonding counterion suggests that hydrogen bonding occurs in solution also. There are two short S-S contacts and small S-Mo-S angles in the structure of 1 that may reflect a slight bonding interaction. Such short S-S distances and small angles have been found in a couple of other Mo-thiolate complexes and in many of the molybdoenzyme crystal structures. Further characterization of 1 by EPR, IR, and UV-vis spectroscopies, as well as by cyclic voltammetry, is discussed and compared to known Mo(V)-oxo-tetrathiolate complexes as well as to relevant molybdoenzyme data. Reactions to generate Mo(VI) complexes from 1 resulted in net oxidation at the ligand to form its disulfide derivative, which dissociated from the metal center. This result suggests that modifications to the ligand to prevent this process are needed.

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Section: Resultsmentioning

confidence: 57%

Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A mononuclear molybdenum(V) mono-oxo biphenyl-2,2′-dithiolate complex in which the metal resides within a cleft formed by the ligands and that exhibits N-H...S hydrogen bonding in the solid state

Conry

Tipton

2001

J. Biol. Inorg. Chem.

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ChemInform Abstract: Chemical and Electrochemical Redox Transformations of Oxomolybdenum and Oxotungsten Tetrathiolate Complexes.

Soong¹,

Chebolu²,

Koch³

et al. 1987

ChemInform

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Why is the molybdenum-substituted tungsten-dependent formaldehyde ferredoxin oxidoreductase not active? A quantum chemical study

Liao

2012

J Biol Inorg Chem

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Formaldehyde ferredoxin oxidoreductase is a tungsten-dependent enzyme that catalyzes the oxidative degradation of formaldehyde to formic acid. The molybdenum ion can be incorporated into the active site to displace the tungsten ion, but is without activity. Density functional calculations have been employed to understand the incapacitation of the enzyme caused by molybdenum substitution. The calculations show that the enzyme with molybdenum (Mo-FOR) has higher redox potential than that with tungsten, which makes the formation of the Mo(VI)=O complex endothermic by 14 kcal/mol. Following our previously suggested mechanism for this enzyme, the formaldehyde substrate oxidation was also investigated for Mo-FOR using the same quantum-mechanics-only model, except for the displacement of tungsten by molybdenum. The calculations demonstrate that formaldehyde oxidation occurs via a sequential two-step mechanism. Similarly to the tungsten-catalyzed reaction, the Mo(VI)=O species performs the nucleophilic attack on the formaldehyde carbon, followed by proton transfer in concert with two-electron reduction of the metal center. The first step is rate-limiting, with a total barrier of 28.2 kcal/mol. The higher barrier is mainly due to the large energy penalty for the formation of the Mo(VI)=O species.

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Chemical and electrochemical redox transformations of oxomolybdenum and oxotungsten tetrathiolate complexes

Cited by 29 publications

References 1 publication

A mononuclear molybdenum(V) mono-oxo biphenyl-2,2′-dithiolate complex in which the metal resides within a cleft formed by the ligands and that exhibits N-H...S hydrogen bonding in the solid state

A mononuclear molybdenum(V) mono-oxo biphenyl-2,2′-dithiolate complex in which the metal resides within a cleft formed by the ligands and that exhibits N-H...S hydrogen bonding in the solid state

ChemInform Abstract: Chemical and Electrochemical Redox Transformations of Oxomolybdenum and Oxotungsten Tetrathiolate Complexes.

Why is the molybdenum-substituted tungsten-dependent formaldehyde ferredoxin oxidoreductase not active? A quantum chemical study

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