CS2 Fixation by Carbonic Anhydrase Model Systems-A New Substrate in the Catalytic Cycle

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• 作者：Sebastian Sinnecker ; Michael Brä ; uer ; Wolfram Koch ; and Ernst Anders
• 刊名：Inorganic Chemistry
• 出版年：2001
• 出版时间：February 26, 2001
• 年：2001
• 卷：40
• 期：5
• 页码：1006 - 1013
• 全文大小：127K
• 年卷期：v.40,no.5(February 26, 2001)
• ISSN：1520-510X

文摘

The conversion of CS₂ with common carbonic anhydrase model systems has been studied using Hartree-Fockand density-functional theory methods employing the 6-311+G* basis set. The calculated geometries and energeticalparameters for [L₃ZnOH]⁺/CS₂ model systems (L = NH₃, imidazole) are compared with those obtained previouslyfor the CO₂ hydration. While the same reaction mechanism applies for both heterocumulenes, the hypotheticalconversion of CS₂ to give [L₃ZnSC(O)SH]⁺ is characterized by a higher barrier and is much more exothermicthan the corresponding CO₂ reaction cascade. Due to the increased number of heteroatoms, additional intermediatesand product structures (compared with those involved in the CO₂ conversion) must be taken into account andhave been analyzed in detail. The smaller electrophilicity of CS₂ is the reason for the higher activation energies,while the significantly increased exothermicity is due to the strong zinc(II)/sulfur interaction. The reversibilityand therefore the existence of a catalytic cycle which could allow comparable CS₂ transformations must bequestioned. Nevertheless, an interesting field of stoichiometric zinc-mediated CS₂ transformations is conceivable.