Asymmetric Oxygenation of a Ruthenium Dithiolate Mimics the Mixed Sulfenato/Sulfinato Donor Sets of Nitrile Hydratase and Thiocyanate Hydrolase

Masitas, César A.; Mashuta, Mark S.; Grapperhaus, Craig A.

doi:10.1021/ic100414c

Cited by 27 publications

(38 citation statements)

References 24 publications

(43 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The precatalysts L 1 RuPPh 3 , L 2 RuPPh 3 , and L 3 RuPPh 3 were synthesized using the established protocols as reported earlier. 18,19 The purity of each complex was confirmed using square wave voltammetry.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Kinetic Effects of Sulfur Oxidation on Catalytic Nitrile Hydration: Nitrile Hydratase Insights from Bioinspired Ruthenium(II) Complexes

2014

Self Cite

View full text Add to dashboard Cite

Kinetic investigations inspired by the metalloenzyme nitrile hydratase were performed on a series of ruthenium(II) complexes to determine the effect of sulfur oxidation on catalytic nitrile hydration. The rate of benzonitrile hydration was quantified as a function of catalyst, nitrile, and water concentrations. Precatalysts L(n)RuPPh3 (n = 1-3; L(1) = 4,7-bis(2'-methyl-2'-mercapto-propyl)-1-thia-4,7-diazacyclononane; L(2) = 4-(2'-methyl-2'-sulfinatopropyl)-7-(2'-methyl-2'-mercapto-propyl)-1-thia-4,7-diazacyclononane; L(3) = 4-(2'-methyl-2'-sulfinatopropyl)-7-(2'-methyl-2'-sulfenato-propyl)-1-thia-4,7-diazacyclononane) were activated by substitution of triphenylphosphine with substrate in hot dimethylformamide solution. Rate measurements are consistent with a dynamic equilibrium between inactive aqua (L(n)Ru-OH2) and active nitrile (L(n)Ru-NCR) derivatives with K = 21 ± 1, 9 ± 0.9, and 23 ± 3 for L(1) to L(3), respectively. Subsequent hydration of the L(n)Ru-NCR intermediate yields the amide product with measured hydration rate constants (k's) of 0.37 ± 0.01, 0.82 ± 0.07, and 1.59 ± 0.12 M(-1) h(-1) for L(1) to L(3), respectively. Temperature dependent studies reveal that sulfur oxidation lowers the enthalpic barrier by 27 kJ/mol, but increases the entropic barrier by 65 J/(mol K). Density functional theory (DFT) calculations (B3LYP/LanL2DZ (Ru); 6-31G(d) (all other atoms)) support a nitrile bound catalytic cycle with lowering of the reaction barrier as a consequence of sulfur oxidation through enhanced nitrile binding and attack of the water nucleophile through a highly organized transition state.

show abstract

Section: ■ Experimental Sectionmentioning

confidence: 99%

Kinetic Effects of Sulfur Oxidation on Catalytic Nitrile Hydration: Nitrile Hydratase Insights from Bioinspired Ruthenium(II) Complexes

2014

Self Cite

View full text Add to dashboard Cite

show abstract

“…Model studies have found stable S-oxygenates of both Fe and Co analogues as well as those of ruthenium. [39][40][41] Air-Sensitivity Studies of [FeFe]H 2 ases As [FeFe]H 2 ases are the most active of the hydrogenases for proton reduction to H 2 , it is reasonable that they should be the most air-sensitive. Thus considerable effort has been expended on understanding the source of their O 2 sensitivity, especially in the photosynthetic green algal organism Chlamydomonas reinhardtii.…”

Section: Nickel Sulfoxygenates As Models Of Oxygendamaged [Nife]h 2 Asementioning

confidence: 99%

Sulfoxygenation of Active Site Models of [NiFe] and [FeFe] Hydrogenases – A Commentary on Possible Chemical Models of Hydrogenase Enzyme Oxygen Sensitivity

Darensbourg

Weigand

2011

Eur J Inorg Chem

View full text Add to dashboard Cite

The organometallic active sites in [NiFe]-and [FeFe]H 2 ases are sensitive to oxygen in varying degrees. The microorganisms that utilize these enzymes for their hydrogen metabolism, and the enzymes themselves, have evolved from a reducing to an oxidizing environment in ways to avoid competition with oxygen, primarily by burying the active site machinery deeply within the protein matrix. In the case of [NiFe]H 2 ase, biological studies indicate that repair mechanisms exist for reversible O 2 -inhibition processes. This Microreview

show abstract

“…The thiolato/sulfinato (2) and sulfenato/sulfinato (3) derivatives display Ru III/II couples at more positive potentials, -0.39 and -0.26 V, respectively, due to the ligand-centered oxidations. [17,18] The Ru(III) derivatives 4 -6 can be prepared by addition of ferrocenium hexafluorophosphate (FcPF 6 ) to the corresponding Ru(II) derivative.…”

Section: Textmentioning

confidence: 99%

Metal-centered oxidation decreases nitrile hydration activity of bioinspired (N2S3)Ru-PPh3 precatalysts

Kumar

Mashuta

Grapperhaus

2015

Inorganic Chemistry Communications

Self Cite

View full text Add to dashboard Cite

A series of ruthenium(II) nitrile hydration catalysts based on the pentadentate ligand 4,7-bis(2'methyl-2'-mercaptopropyl)-1-thia-4,7-diazacyclononane and its sulfur-oxidized derivatives have been oxidized at the metal center yielding the ruthenium(III) counterparts. Metal-centered oxidation results in complete loss of nitrile hydration activity for the dithiolato (RS-/RS-) parent complex. The sulfuroxidized thiolato/sulfinato (RS-,RSO 2-) derivative displays a decrease in turnover number from 238 ± 23 to 3 ± 1 upon oxidation of Ru(II) to Ru(III). A similar decrease in turnover number from 242 ± 23 to 7 ± 3 is observed upon metal-centered oxidation of the sulfenato/sulfinato (RSO-,RSO 2-) derivative. The inactive complex [(4,7-bis(2'-methyl-2'-mercaptopropyl)-1-thia-4,7-diazacyclononane)(triphenylphosphine)ruthenium(III)]hexafluorophosphate has been synthesized and characterized by electronic spectroscopy, electron paramagnetic resonance, and single crystal x-ray diffraction studies.

show abstract

Asymmetric Oxygenation of a Ruthenium Dithiolate Mimics the Mixed Sulfenato/Sulfinato Donor Sets of Nitrile Hydratase and Thiocyanate Hydrolase

Cited by 27 publications

References 24 publications

Kinetic Effects of Sulfur Oxidation on Catalytic Nitrile Hydration: Nitrile Hydratase Insights from Bioinspired Ruthenium(II) Complexes

Kinetic Effects of Sulfur Oxidation on Catalytic Nitrile Hydration: Nitrile Hydratase Insights from Bioinspired Ruthenium(II) Complexes

Sulfoxygenation of Active Site Models of [NiFe] and [FeFe] Hydrogenases – A Commentary on Possible Chemical Models of Hydrogenase Enzyme Oxygen Sensitivity

Metal-centered oxidation decreases nitrile hydration activity of bioinspired (N2S3)Ru-PPh3 precatalysts

Contact Info

Product

Resources

About