Zinc Thiolate Complexes [ZnLn(SR)]+ with Azamacrocyclic Ligands, Part II: Mechanism of the Reaction with CS2

Notni, Johannes; Schenk, Stephan; Roth, Arne; Plass, Winfried; Görls, Helmar; Uhlemann, Ute; Walter, Axel; Schmitt, Michael; Popp, Jürgen; Chatzipapadopoulos, Susana; Emmler, Thomas; Breitzke, Hergen; Leppert, Jörg; Buntkowsky, Gerd; Kempe, Kristian; Anders, Ernst

doi:10.1002/ejic.200500948

Cited by 11 publications

(17 citation statements)

References 31 publications

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“…Attack of the zinc‐bound hydroxide occurs exclusively at the CS bond and results in a four‐centre transition structure, whereby a zinc‐bound thiocarbonate [(NH 3 ) 3 Zn{S‐C(O)‐OH}] + is formed. Although this structure could not be observed in an experimental investigation until now, there is more than circumstantial evidence for its intermediate existence from the detailed calculations and related structures observed in experiments 10b. CO 2 is formed by a water‐assisted proton transfer, then expelled, and the zinc hydrosulfide complex [(NH 3 ) 3 ZnSH] + is obtained.…”

Section: Introductionmentioning

confidence: 89%

The Missing Link in COS Metabolism: A Model Study on the Reactivation of Carbonic Anhydrase from its Hydrosulfide Analogue

et al. 2007

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Carbonic anhydrase (CA) is known to react with carbonyl sulfide, an atmospheric trace gas, whereby H(2)S is formed. It has been shown that, in the course of this reaction, the active catalyst, the His(3)ZnOH structural motif, is converted to its hydrosulfide form: His(3)ZnOH+COS-->His(3)ZnSH+CO(2). In this study, we elucidate the mechanism of reactivation of carbonic anhydrase (CA) from its hydrosulfide analogue by using density functional calculations, a model reaction and in vivo experimental investigation. The desulfuration occurs according to the overall equation His(3)ZnSH+H(2)O right harpoon over left harpoon His(3)ZnOH+H(2)S. The initial step is a protonation equilibrium at the zinc-bound hydrosulfide. The hydrogen sulfide ligand thus formed is then replaced by a water molecule, which is subsequently deprotonated to yield the reactivated catalytic centre of CA. Such a mechanism is thought to enable a plant cell to expel H(2)S or rapidly metabolise it to cysteine via the cysteine synthase complex. The proposed mechanism of desulfuration of the hydrosulfide analogue of CA can thus be regarded as the missing link between COS consumption of plants and their sulfur metabolism.

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Section: Introductionmentioning

confidence: 89%

The Missing Link in COS Metabolism: A Model Study on the Reactivation of Carbonic Anhydrase from its Hydrosulfide Analogue

et al. 2007

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“…30 As an example, Scheme 4 shows the molecular structures of a thiolate complex and the corresponding trithiocarbonate complex resulting from the insertion of CS 2 . 30 As an example, Scheme 4 shows the molecular structures of a thiolate complex and the corresponding trithiocarbonate complex resulting from the insertion of CS 2 .…”

Section: Heterocumulene Reactions Of the Zinc-bound Sulfurmentioning

confidence: 99%

Carbon dioxide and related heterocumulenes at zinc and lithium cations: bioinspired reactions and principles

et al. 2006

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This Perspective starts with the discussion of the properties of an interesting metalloenzyme (carbonic anhydrase, CA) that performs extremely successfully the activation of carbon dioxide. Conclusions from that are important for many synthetic procedures and include experimental and theoretical investigation (DFT calculations) of such metal mediated processes in the condensed and in the gas phase in which the zinc cation plays a dominant role. This is extended to the bio-analogue activation of further heterocumulenes such as COS, an important atmospheric trace gas, and CS(2). Novel metal complexes which serve as useful catalysts for the reactions (copolymerisations and cyclisation) of CO(2) and oxiranes are discussed subject to the inclusion of recently published DFT calculations. We continue with the discussion of the very general aspect of the insertion of CO(2) into metal-nitrogen bonds (formation of carbamates). This again is closely related to many biological or bio-analogue processes. We describe the synthesis and mechanistic aspects of characteristic metal carbamates of a wide variety of metals and include a discussion of the mechanistic aspects, especially for the formation of Mg(2+) and Li(+) carbamates and the formation of related cyclic products after addition of the heterocumulenes CO(2), Ph-NCO or CS(2) to novel ligands, the 4H-pyridin-1-ides which finally result in the formation of e.g. 1,3-thiazole-5(2H)-thiones.

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“…Recently, we introduced a series of novel zinc thiolate complexes [1] that are ideally suited for these investigations for several reasons: 11 different compounds meeting the experimental requirements are currently available; they fea- [21] ) were found to occur cleanly and on a convenient time scale; they comprise a sufficiently small number of non-hydrogen atoms to be suited for investigation by high-level density functional calculations. The latter instance offers the possibility to reveal the effect especially of electronic parameters that are only accessible by computation, for example, orbital energies and partial charges.…”

Section: Introductionmentioning

confidence: 99%

Zinc Thiolate Complexes [ZnL_n(SR)]⁺ with Azamacrocyclic Ligands, Part III: The Influence of the Ligand L_n on the Reactivity of Zinc‐Bound Thiolate

2007

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In this study, we focus on the structure-reactivity relationship of cationic zinc thiolate complexes with the general formula [Zn(L n )(SR)]ClO 4 (L n : n-dentate azamacrocyclic ligand; R = phenylmethyl). The complexes feature macrocyclic ligands with ring sizes varying from 11 to 16 atoms and possess three or four nitrogen donors (three of them containing one tertiary nitrogen). Thiol methylations with methyl iodide have been performed in order to determine the relative reactivities, because this reaction has been used before to investigate zinc thiolate reactivity and therefore allows comparison of our results with literature data. The kinetic behaviour was investigated in nitromethane and dichloromethane and was found to be second order in all cases. The observed rate constants vary in the range of k 2 = 2.46-55.28ϫ10 -1 in dichloromethane at 300 K. Furthermore, the structures of all thiolate complexes were optimised at the B3LYP/6-311+G(d) level of theory. Natural bond orbital (NBO) analyses were performed to obtain information on partial charges of the heteroatoms

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Zinc Thiolate Complexes [ZnL_n(SR)]⁺ with Azamacrocyclic Ligands, Part II: Mechanism of the Reaction with CS₂

Abstract: The thiolate complexes [Zn([15]

Cited by 11 publications

References 31 publications

The Missing Link in COS Metabolism: A Model Study on the Reactivation of Carbonic Anhydrase from its Hydrosulfide Analogue

The Missing Link in COS Metabolism: A Model Study on the Reactivation of Carbonic Anhydrase from its Hydrosulfide Analogue

Carbon dioxide and related heterocumulenes at zinc and lithium cations: bioinspired reactions and principles

Zinc Thiolate Complexes [ZnL_n(SR)]⁺ with Azamacrocyclic Ligands, Part III: The Influence of the Ligand L_n on the Reactivity of Zinc‐Bound Thiolate

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Zinc Thiolate Complexes [ZnLn(SR)]+ with Azamacrocyclic Ligands, Part II: Mechanism of the Reaction with CS2

Abstract: The thiolate complexes [Zn([15]

Cited by 11 publications

References 31 publications

The Missing Link in COS Metabolism: A Model Study on the Reactivation of Carbonic Anhydrase from its Hydrosulfide Analogue

The Missing Link in COS Metabolism: A Model Study on the Reactivation of Carbonic Anhydrase from its Hydrosulfide Analogue

Carbon dioxide and related heterocumulenes at zinc and lithium cations: bioinspired reactions and principles

Zinc Thiolate Complexes [ZnLn(SR)]+ with Azamacrocyclic Ligands, Part III: The Influence of the Ligand Ln on the Reactivity of Zinc‐Bound Thiolate

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Zinc Thiolate Complexes [ZnL_n(SR)]⁺ with Azamacrocyclic Ligands, Part II: Mechanism of the Reaction with CS₂

Zinc Thiolate Complexes [ZnL_n(SR)]⁺ with Azamacrocyclic Ligands, Part III: The Influence of the Ligand L_n on the Reactivity of Zinc‐Bound Thiolate