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  • 學位論文

鎳-硫化合物之合成與反應性:鎳/鐵氫化酵素之鎳活化中心之生化擬態模型化合物

Synthesis and reactivity of Nickel(III)-thiolate complexes: relevance to the Nickel site of [NiFe] Hydrogenase

指導教授 : 廖文峯
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摘要


取等比例的[PPN][Ni(CO)(2-S-C4H3S)3]和P(C6H3-3-SiMe3-2-SH)3在THF溶液中反應,可形成[PPN][NiII(2-S-C4H3S)P((C6H3-3-SiMe3-2-S)2(C6H3-3-SiMe3-2- SH))] (1),而取等比例的NiCl2(PPh3)2和P(C6H3-3-SiMe3-2-SH)3在THF溶液中反應,則可得到[NiII(PPh3)P((C6H3-3-SiMe3-2-S)2(C6H3-3-SiMe3-2-SH))] (3)。這兩個NiII化合物為四配位,扭曲平面四邊形結構。其中,pendant thiol與Ni和Ni上的S原子會產生分子內交互作用力。經由X-ray單晶繞射鑑定結構和光譜分析,證實化合物1具有[Ni…H-S](1a)/ [Ni-S…H-S](1b)分子內的交互作用力,而化合物3的分子內作用力則屬於[Ni…H-S]交互作用力。 化合物1、3 通入O2後,會分別形成[PPN][NiIII(2-S-C4H3S)P((C6H3-3-SiMe3- 2-S)3)] (2)和[NiIII(PPh3)(P((C6H3-3-SiMe3-2-S)3)] (4),皆為五配位,扭曲雙三角錐結構。化合物2在CH2Cl2溶液時,CH2Cl2會行dechlorination反應,化合物2會轉換成[PPN][NiIII(Cl)P((C6H3-3-SiMe3-2-S)3)]。在CO的環境下,化合物2會行reductive elimination,產生[PPN][NiII(CO)P((C6H3-3-SiMe3-2-S)3)]。而因為化合物4的terminal ligand是PPh3,是中性且是一個供給電子能力較弱的ligand,使其在CH2Cl2溶液中無法轉變成[PPN][NiIII(Cl)P((C6H3-3-SiMe3-2-S)3)],且在CO的環境下也無法行reductive elimination,產生[PPN][NiII(CO)P((C6H3-3-SiMe3-2- S)3)]。利用環電位儀(Cyclic Voltammetry)測化合物2、4的NiIII/II氧化還原電位分別為-1.16 V、-0.83 V (vs Cp2Fe/Cp2Fe+),皆為可逆的反應。對於這幾個化合物的幾何結構、光譜特性與反應機制可以對鎳鐵-氫化酵素做有意義的解釋。

關鍵字

金屬酵素 氫化酵素

並列摘要


The reaction of [PPN][Ni(CO)(2-S-C4H3S)3] with 1 equiv of P(C6H3-3-SiMe3-2- SH)3 in THF leads to form the four-coordinated complex, [PPN][NiII(2-S-C4H3S)P- ((C6H3-3-SiMe3-2-S)2(C6H3-3-SiMe3-2-SH))] (1). In the same preparation way, the reaction of NiCl2(PPh3)2 with 1 equiv of P(C6H3-3-SiMe3-2-SH)3 in THF leads to yield another four-coordinated complex, [NiII(PPh3)P((C6H3-3-SiMe3-2-S)2(C6H3-3- SiMe3-2-SH))] (3). Complexes 1 and 3 display a similar structural geometry, distorted square planar with a S-H proton interacting with both nickel center and sulfur atom. The presence of intramolecular [Ni…H-S]/[Ni-S…H-S] interactions in complexes 1 and 3 were verified in the solid state by the observation of the lower IR vS-H band and further confirmed by X-ray study. Oxidation of complexes 1 and 3 by O2 results in the formation of a mononuclear, distorted triganol bipyramidal [PPN][NiIII(2-S-C4H3S)- P((C6H3-3-SiMe3-2-S)3)] (2) and [NiIII(PPh3)(P((C6H3-3-SiMe3-2-S)3)] (4), respectively. Complex 2 undergoes dechlorination of CH2Cl2 solution to generate [PPN][NiIII(Cl)P((C6H3-3-SiMe3-2-S)3)]. In addition, complex 2 reacts with exogenous CO to produce [PPN][NiII(CO)P((C6H3-3-SiMe3-2-S)3)]. In contrast to complex 2, complex 4 is inert in the presence of CH2Cl2 and CO. This results imply that PPh3 is a weaker donating ligand than thiolate ligand (2-S-C4H3S). This result is further confirmed by the result of the cyclic voltammograms of complex 2 and 4. Complexes 2 and 4 display a reversible NiIII/II redox processes with E1/2 = -1.16 V, -0.83 V (vs Cp2Fe/ Cp2Fe+), respectively. The structure, activity, and spectroscopic properties of these complexes may show some insight about the nickel site in bimetallic Ni-Fe active site of [NiFe] Hydrogenase.

並列關鍵字

metalloenzyme hydrogenase

參考文獻


1. (a) Adams, M. W. W.; Stiefel, E. I. Curr. Opin. Chem. Biol. 2000, 4, 214-220. (b) Casalot, L; Rousset, M. TRENDS in Microbiol. 2001, 9, 228-237.
2. (a)Volbeda, A.; Charon, M. H.; Piras, C.; Hatchikian, E. C.; Frey, M.; Fontecilla-
Camps, J. C. Nature 1995, 373, 580-587. (b) Happe, R. P.; Roseboom, W.; Pierik,
A. J.; Albracht, S. P. J Nature 1997, 385, 126.
3. (a) Higuchi, Y.; Yagi, T.; Yasuoka, N. Structure 1997, 5, 1671-1680. (b) Higuchi, Y.; Ogata, H.; Miki, K.; Yasuoka, N.; Yagi, T. Structure 1999, 7, 549-556.

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