雙核與單核鎳-硫錯合物：鎳-鐵氫化酵素生物擬態模型化合物

Dinuclear and Mononuclear Nickel-Thiolate Complexes:Model Compounds of [NiFe] Hydrogenases

邱宗文(Tzung-Wen Chiou)

指導教授 ： 廖文峯

國立清華大學/理學院/化學系/碩士(2007年)

摘要

取等當量的[NiIII(P(o-C6H3-3-SiMe3-2-S)3)]2和NaBEt3H以及過量的18-crown- 6-ether溶於THF中，可得到[Na-18-crown-6-ether][Ni2(P(o-C6H3-3-SiMe3 -2-S)3)2] (1)，再者以1：4的比例將[PPN]2[NiCl4]和NaSEt溶於CH3CN中，再加入一當量的P(o-C6H3-3-SiMe3-2-SH)3 ligand，即可得到[PPN]2[Ni2(P(o-C6H3-3-SiMe3- 2-S)3)2] (2)。化合物1及2的陰離子部分，中心部份分別是mixed-valence [Ni(II)- Ni(III)]及[Ni(II)-Ni(II)]，以及起始物[NiIII(P(o-C6H3-3-SiMe3-2-S)3)]2的[Ni(III)- Ni(III)]，我們可以從這三個化合物中心金屬隨著電子數的增加，比較這三者的配位結構、光譜，以及兩個Nickel距離的變化，來印証鐵鎳氫化酵素([NiFe] Hydrogenase)在其氧化態改變時，中心位置[NiS2Fe] core的組態變化。
[NiIII(PPh3)(P(o-C6H4S)3)]、KC8及18-crown-6-ether以1：1：2的比例溶在THF溶液中，還原成[K-18-crown-6][NiII(PPh3)(P(C6H4-2-S)3)] (3)。化合物3是Ni二價五配位的結構，由於金屬中心電子密度過高，導致陽離子與Ligand上其中一個硫原子有些許的作用，使得Ni-S配位距離拉長許多，使整個五配位環境能夠穩定。
以1：3的比例將[PPN][NiIII(Cl)(P(o-C6H3-3-SiMe3-2-S)3)]和[Na][O-C6H5]溶於THF-CH3CN中，可得到[PPN][NiIII(O-C6H5)(P(o-C6H3-3-SiMe3-2-S)3)] (4)，再者以相同的手法，將等當量的[PPN][NiIII(Cl)(P(o-C6H3-3-SiMe3-2-S)3)]和[Na][S-C6H5]溶於THF-CH3CN中，可得到[PPN][NiIII(S-C6H5)(P(o-C6H3-3-SiMe3-2-S)3)] (5)。化合物4和5皆是Ni三價五配位結構，其中化合物4是目前第一個NiIII-thiolate- OR complex，對於鐵鎳氫化酵素([NiFe] Hydrogenase)氧化態擬態化合物是一大突破。再者化合物4和5以及實驗室之前所合成的[PPN][NiIII(Se-C6H5)(P(o-C6H3- 3-SiMe3-2-S)3)]，這三者的晶體結構、反應性質和光譜性質皆可做一系列的比較，來探討O、S、Se這三個原子對於Ni的配位性質有何差異。

關鍵字

氫化酵素 ； 鎳鐵-氫化酵素 ； 鎳 ； 鎳硫錯合物 ； 生物擬態模型化合物

並列摘要

The reaction of [NiIII(P(o-C6H3-3-SiMe3-2-S)3)]2 and NaBEt3H in 1:1 molar ratio and excess 18-crown-6-ether in THF led to the formation of complex [Na-18-crown-6 -ether][Ni2(P(o-C6H3-3-SiMe3-2-S)3)2] (1). The [PPN]2[NiCl4] and NaSEt in 1:4 molar ratio were dissolved in CH3CN and then added the P(o-C6H3-3-SiMe3-2-SH)3 ligand into solution to yield [PPN]2[Ni2(P(o-C6H3-3-SiMe3-2-S)3)2] (2). The core of complexes 1 and 2 were mixed-valence [Ni(II)-Ni(III)] and localized [Ni(II)-Ni(II)], respectively.
The reaction of [NiIII(PPh3)(P(o-C6H4S)3)], KC8, and 18-crown-6-ether in 1:1:2 molar ratio in THF yielded the five-coordinated complex, [K-18-crown-6][NiII(PPh3) (P(C6H4-2-S)3)] (3). The interaction between potassium and sulfur decreasing electronic density of metal center may play a key role in stabilizing complex 3.
The five-coordinated complex [PPN][NiIII(O-C6H5)(P(o-C6H3-3-SiMe3-2-S)3)] (4) was prepared by the reaction of [PPN][NiIII(Cl)(P(o-C6H3-3-SiMe3-2-S)3)] and [Na][O-C6H5] in 1:3 molar ratio in THF-CH3CN. In a similar fashion, the reaction of [PPN][NiIII(Cl)(P(o-C6H3-3-SiMe3-2-S)3)] and [Na][S-C6H5] in 1:1 molar ratio in THF-CH3CN produced the five-coordinated complex [PPN][NiIII(S-C6H5)(P(o-C6H3 -3-SiMe3-2-S)3)] (5). Complex 4 was the first nickel(III)-thiolate-OR model compound mimicking the oxidized-state active site structure of the [NiFe] hydrogenase. The series of structural and spectral data were compared among those NiIII-X (X = O, S, Se) bond lengths of complexes 4, 5 and [PPN][NiIII(Se-C6H5)(P(o -C6H3-3-SiMe3-2-S)3)].

並列關鍵字

Hydrogenase ； [NiFe] hydrogenase ； Nickel ； Nickel-thiolate complexes ； Model compounds

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