Synthesis of a S-bonded sulfinic acid complex of cobalt(III) by an oxidative route.  A structural trans effect in (2-sulfinatoethylamine-N,S)bis(ethylenediamine)cobalt(III) perchlorate nitrate

Lange, Bruce A.; Libson, Karen; Deutsch, Edward; Elder, R. C.

doi:10.1021/ic50166a007

Cited by 72 publications

(35 citation statements)

References 8 publications

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“…4) and their hypothetical LS Fe III counterparts, where X is a thiolate, sulfenate, sulfenic acid, or sulnate group. [24][25][26] These results provide insight into the relative energy ordering of the LMCT transitions for the different sulfur ligands. We use the subsequently assigned experimental data to calibrate DFT models of the butyrate bound and active forms of NHase and to extend these computational models to examine potential mechanisms for nitrile hydrolysis.…”

Section: Introductionmentioning

confidence: 92%

“…There has been an interesting study of the UV-Vis absorption spectra of a series of LS Co III complexes [(en) 2 Co(XCH 2 CH 2 -NH 2 )-N,S] 2+/3+ , where X is S À , S-coordinated SO À , S-coordinated SOH, and S-coordinated SO 2 À . [24][25][26] This series provides a complete set of spectroscopic data for the thiolate-based ligands of interest for which the computational extension to the hypothetical LS Fe III forms is straightforward. The observed LMCT's are given in Table 2.…”

Section: Ls Co III and Fe Iii Models: Bonding Interactions And Their ...mentioning

confidence: 99%

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Spectroscopic and computational studies of nitrile hydratase: insights into geometric and electronic structure and the mechanism of amide synthesis

et al. 2015

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Nitrile hydratases (NHases) are mononuclear nonheme enzymes that catalyze the hydration of nitriles to amides. NHase is unusual in that it utilizes a low-spin (LS) FeIII center and a unique ligand set comprised of two deprotonated backbone amides, cysteine-based sulfenic acid (RSO(H)) and sulfinic acid (RSO2−), and an unmodified cysteine trans to an exogenous ligand site. Electron paramagnetic resonance (EPR), magnetic circular dichroism (MCD) and low-temperature absorption (LT-Abs) spectroscopies are used to determine the geometric and electronic structures of butyrate-bound (NHaseBA) and active (NHaseAq) NHase. These data calibrate DFT models, which are then extended to explore the mechanism of nitrile hydration by NHase. In particular, the nitrile is activated by coordination to the LS FeIII and the sulfenate group is found to be deprotonated and a significantly better nucleophile than water that can attack the coordinated nitrile to form a cyclic species. Attack at the sulfenate S atom of the cyclic species is favorable and leads to a lower kinetic barrier than attack by water on coordinated, uncyclized nitrile, while attack at the C of the cyclic species is unfavorable. The roles of the unique ligand set and low-spin nature of the NHase active site in function are also explored. It is found that the oxidized thiolate ligands are crucial to maintaining the LS state, which is important in the binding and activation of nitrile susbtrates. The dominant role of the backbone amidate ligands appears to be as a chelate in keeping the sulfenate properly oriented for nucleophilic attack on the coordinated substrate.

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Section: Introductionmentioning

confidence: 92%

Section: Ls Co III and Fe Iii Models: Bonding Interactions And Their ...mentioning

confidence: 99%

Spectroscopic and computational studies of nitrile hydratase: insights into geometric and electronic structure and the mechanism of amide synthesis

et al. 2015

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“…The axial positions are occupied by two deprotonated amide nitrogen atoms (Co–N(1) = 1.942(2), Co–N(2) = 1.928(2) Å). The Co–S(2) bond (2.1329(6) Å) of 2 is somewhat shorter than Co–S bonds of other six-coordinate complexes with sulfinyl S-coordination (2.164–2.232 Å) ,,,− as well as the Co–S(O 2 ) bond length (2.118(1) Å) in [Co(III)((η 2 -SO)(S O2 )N 3 (Pr,Pr))] + . The inclined coordination of the sulfenyl oxygen (Co–O(3) = 2.044(2) Å) by η 2 -coordination may have the effect of shortening the Co–S(O 2 ) bond.…”

Section: Resultsmentioning

confidence: 98%

Co(III) Complexes with N₂S₃-Type Ligands as Structural/Functional Models for the Isocyanide Hydrolysis Reaction Catalyzed by Nitrile Hydratase

et al. 2018

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It has been before reported that, in addition to hydration of nitriles, the Fe-type nitrile hydratase (NHase) also catalyzes the hydrolysis of tert-butylisocyanide ( tBuNC). In order to investigate the unique isocyanide hydrolysis by NHase, we prepared three related Co(III) model complexes, PPh[Co(L)] (1), PPh[Co(L-O)] (2), and PPh[Co(L-O)] (3), where L is bis( N-(2-mercapto-2-methylpropionyl)aminopropyl)sulfide. The suffixes L-O and L-O indicate ligands with a sulfenate and a sulfinate and with two sulfinates, respectively, instead of the two thiolates of L. The X-ray analyses of 1 and 3 reveal trigonal bipyramidal and square pyramidal structures, respectively. Complex 2, however, has five-coordinate trigonal-bipyramidal geometry with η-type S-O coordination by a sulfenyl group. Addition of tBuNC to 1, 2, and 3 induces an absorption spectral change as a result of formation of an octahedral Co(III) complex. This interpretation is also supported by the crystal structures of PPh[Co(L-O)( tBuNC)] (4) and (PPh)[Co(L-O)(CN)] (5). A water molecule interacts with 3 but cannot be activated as reported previously, as demonstrated by the lack of absorption spectral change in the pH range of 5.5-10.2. Interestingly, the coordinated tBuNC is hydrolyzed by 2 and 3 at pH 10.2 to produce tBuNH and CO molecule, but 1 does not react. These findings provide strong evidence that hydrolysis of tBuNC by NHase proceeds not by activation of the coordinated water molecule but by coordination of the substrate. The mechanism of the hydrolysis reaction of tBuNC is explained with support provided by DFT calculations; a positively polarized C atom of tBuNC on the Co(III) center is nucleophilically attacked by a hydroxide anion activated through an interaction of the sulfenyl/sulfinyl oxygen with the nucleophile.

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“…The absorption at 2500 cm −1 for the S-H stretching vibration for the free L-sys ligand is absent in 1, which indicates the that L-cysteine has coordinated to cobalt(III) ion via the S donor atom. 9,10 The electronic absorption spectra are particularly helpful in determining whether the sulfur atom is coordinated or uncoordinated. 4,[11][12][13] The absorption spectrum of 1 (Figure 2) shows the λmax in the A 1g→ T 1g (O h ) region at 576 nm which is expected for a CoN 3 O 2 S system, [14][15][16][17][18][19] indicating that coordination of L-cysteine has taken place through nitrogen and sulfur donor atoms in 1.…”

Section: Resultsmentioning

confidence: 99%

L-Cysteinesulfenato and L-Cysteinesulfinato Cobalt(Ⅲ) Complexes of N,N'-Dimethylethylenediamine-N,N'-diacetic Acid

Park¹,

Yang²,

Jun³

2002

Bulletin of the Korean Chemical Society

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Synthesis of a S-bonded sulfinic acid complex of cobalt(III) by an oxidative route. A structural trans effect in (2-sulfinatoethylamine-N,S)bis(ethylenediamine)cobalt(III) perchlorate nitrate

Abstract: Die Behandlung des 2‐Aminoäthanthiolato‐Co(III)‐ Komplexes (I) mit H2O, führt zur Oxidation des koordinierten S‐Atoms unter Bildung des Sulfinato‐Co(III)‐perchlorats (IIa), das durch Metathese in die entsprechenden Salze (IIb) und (II c) umwandelbar ist.

Cited by 72 publications

References 8 publications

Spectroscopic and computational studies of nitrile hydratase: insights into geometric and electronic structure and the mechanism of amide synthesis

Spectroscopic and computational studies of nitrile hydratase: insights into geometric and electronic structure and the mechanism of amide synthesis

Co(III) Complexes with N₂S₃-Type Ligands as Structural/Functional Models for the Isocyanide Hydrolysis Reaction Catalyzed by Nitrile Hydratase

L-Cysteinesulfenato and L-Cysteinesulfinato Cobalt(Ⅲ) Complexes of N,N'-Dimethylethylenediamine-N,N'-diacetic Acid

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Synthesis of a S-bonded sulfinic acid complex of cobalt(III) by an oxidative route. A structural trans effect in (2-sulfinatoethylamine-N,S)bis(ethylenediamine)cobalt(III) perchlorate nitrate

Abstract: Die Behandlung des 2‐Aminoäthanthiolato‐Co(III)‐ Komplexes (I) mit H2O, führt zur Oxidation des koordinierten S‐Atoms unter Bildung des Sulfinato‐Co(III)‐perchlorats (IIa), das durch Metathese in die entsprechenden Salze (IIb) und (II c) umwandelbar ist.

Cited by 72 publications

References 8 publications

Spectroscopic and computational studies of nitrile hydratase: insights into geometric and electronic structure and the mechanism of amide synthesis

Spectroscopic and computational studies of nitrile hydratase: insights into geometric and electronic structure and the mechanism of amide synthesis

Co(III) Complexes with N2S3-Type Ligands as Structural/Functional Models for the Isocyanide Hydrolysis Reaction Catalyzed by Nitrile Hydratase

L-Cysteinesulfenato and L-Cysteinesulfinato Cobalt(Ⅲ) Complexes of N,N'-Dimethylethylenediamine-N,N'-diacetic Acid

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Co(III) Complexes with N₂S₃-Type Ligands as Structural/Functional Models for the Isocyanide Hydrolysis Reaction Catalyzed by Nitrile Hydratase