生物擬態{Fe(NO)2}9雙亞硝基鐵含[S,S]/ [O,O]/ [N,O]/ [S,O]配位基化合物:化合物結構、穩定性、反應性與相互轉換的探討

The Biomimetic {Fe(NO)2}9 Dinitrosyl Iron Complexes (DNICs) with [S,S]/ [O,O]/ [N,O]/ [S,O] Ligations: Structure, Stability, Reactivity and its Interconversion

蔡銘哲(Ming-Che Tsai)

指導教授 ： 廖文峰

國立清華大學/理學院/化學系/博士(2008年)

https://doi.org/10.6843/NTHU.2008.00125

摘要

藉由[Fe(CO)2(NO)2]加入不同含phosphorus/nitrogen的配位基做反應，例如：
PPh3, ethylenediamine, TMEDA與sparteine，分別可以得到neutral {Fe(NO)2}10 [(PPh3)2Fe(NO)2] (3)、[(ethylenediamine)Fe(NO)2] (5)、[(TMEDA)Fe(NO)2] (4)與[(sparteine)Fe(NO)2] (15)，利用化合物3加入thiol與thiolate在溫度為45 ℃的情況下可以合成anionic {Fe(NO)2}9 [(SPh)2Fe(NO)2]- (1)與 [(4-ClC6H4S)2Fe(NO)2]- (2)，亦可利用所合成的化合物1與2加入PPh3與還原劑sodium biphenyl將之轉換為化合物3，了解{Fe(NO)2}10與{Fe(NO)2}9之間可以相互轉換生成；而化合物4與5分別加入PPh3在室溫下經由配位基交換亦可轉換為化合物3，推測為{Fe(NO)2}10 motif 的一氧化氮傾向NO+而鐵的價數為Fe-2，根據HSAB理論Fe-2為soft acid而PPh3相較TMEDA與ethylenediamine為soft base，所以容易被置換形成化合物3而穩定；化合物4加入ethylenediamine可以置換成化合物5，乃由於ethylenediamine的立體效應小於TMEDA造成配位基取代而生成化合物5。
利用化合物[PPN]2[S5Fe(μ-S)2FeS5] (6)加入不同碳鏈數的bidentate alkyl
thiolate與thiol可以得到不同碳鏈數的生化擬態[2Fe-2S] cluster [PPN]2[(S(CH2)nS)Fe(μ-S)2Fe(S(CH2)nS)] (( n = 2(7), 3(8), 4(9), 6(10))，由不同的碳鏈數所形成的生化擬態ferredoxin 其在UV-Vis吸收位置相似但穩定性卻有差異，一般而言，鍵結在Fe上配位基含有較長碳鏈數的thiolate則愈穩定，反之若是較短碳鏈數則愈不穩定。合成含有bidentate alkyl thiolate DNICs [S(CH2)nSFe(NO)2]- (( n = 2(11), 3(12), 4(13), 6(14))可以使用化合物7, 8, 9,與10加入PPh3與NO(g)來合成，或是利用先前合成出來的化合物15，將之氧化形成化合物[(sparteine)Fe(NO)2]+ (16)，再加入不同碳鏈數的thiolate而生成化合物11, 12, 13,與14，另外化合物16與化合物1反應可以得到雙核的RRE [Fe2(μ-SPh)2(NO)4] (17)，由上述得知化合物16可視為一個{Fe(NO)2}的提供者。化合物2, 8, 12,與15經由紅外線/紫外線-可見光光譜儀及單晶X光繞射結構的鑑定。
Anionic {Fe(NO)2}9 [(Cl)(p-FPhO)Fe(NO)2]- (21)、[(p-FPhO)2Fe(NO)2]- (26)
與[(OPh)2Fe(NO)2]- (23)的成功合成證實含tyrosine之protein-bound DNICs存在的可能性。藉由化合物[Fe(Cl)3(NO)]- (18)加入三倍量的[Na][p-FOPh]可以合成化合物21；利用化合物21加入[Na][NO2]與[Na][p-FOPh]反應生成化合物26，乃因[Na]+與[Cl]-結合力較佳，使得[Na][NO2]先與化合物21的Cl-反應生成[(NO2)(p-FOPh)Fe(NO)2]-的中間產物，此時加入的[Na][p-FOPh]較[NO2]-為強的σ-donor與π-donor配位基，因而產生化合物26，且化合物23合成的方式與化合物26相同。將所合成的化合物23加入電子提供能力較強的thiolate如[SPh]-及[-SC4H3S]-，可以置換化合物23成為不對稱的[(PhO)(SPh)Fe(NO)2]- (27)與 [(-SC4H3S)(OPh)Fe(NO)2]- (28)，另外若將化合物23加入較強的σ-donor與π-donor配位基如[C3H3N2]-，可以產生化合物[(PhO)(C3H3N2)Fe(NO)2]- (25)與[(C3H3N2)2Fe(NO)2]- (29)。所得到化合物21, 23, 26, 27,與28在電子順磁共振光譜(EPR)中都出現清楚的五根分裂，而化合物25與29在EPR訊號中出現九根分裂，且其gav約在2.03 ± 0.004範圍內。對於一系列化合物的穩定度做比較得知化合物1為最穩定，其次為[(SPh)(C3H3N2)Fe(NO)2]-、29、27、25、23、[(NO2)2Fe(NO)2]- (22)。化合物21, 23, 26, 27與28經由紅外線/紫外線-可見光光譜儀及單晶X光繞射結構的鑑定。從X-ray data比較化合物1, 23, 26與[(SePh)2Fe(NO)2]-間Fe-S, Fe-O,與Fe-Se間的鍵長得知，化合物26 Fe-O間的鍵長最短而Fe-Se間的鍵長最長，此現象可能與電子提供能力的強弱有關。就NO stretching frequency separation (△νNO)而言，以O/Cl, O/O或N/O做配位的化合物21, 23, 25與26 DNICs其△νNO 約為65 cm-1；以S/S或是Se/Se做配位的化合物1與[(SePh)2Fe(NO)2]- DNICs其△νNO 約為45 cm-1；而以S/O做配位的化合物27與28 DNICs其△νNO 約為55 cm-1。

關鍵字

一氧化氮 ； 雙亞硝基鐵化合物 ； 化合物穩定度 ； 化合物反應性 ； 化合物相互轉換機制

並列摘要

Reaction of complex [Fe(CO)2(NO)2] with phosphorus or
nitrogen-containing ligands such as PPh3, ethylenediamine, TMEDA and sparteine, led to the formation of the neutral {Fe(NO)2}10 [(PPh3)2Fe(NO)2] (3)、[(ethylenediamine)Fe(NO)2] (5)、[(TMEDA)Fe(NO)2] (4) and [(sparteine)Fe(NO)2] (15). Reaction of complex 3 with thiol and thiolate at 45 ℃ lead to the formation of the anionic {Fe(NO)2}9 DNICs [(SPh)2Fe(NO)2]- (1) and [(4-ClC6H4S)2Fe(NO)2]- (2). These two complexes can be converted to the complex 3 by addition of PPh3 and sodium biphenyl. This study demonstrates that the anionic {Fe(NO)2}9 and the neutral {Fe(NO)2}10 DNICs are interconvertable. Furthermore, the neutral {Fe(NO)2}10 complex 4 or 5 can also be converted to the neutral {Fe(NO)2}10 complex 3 under the presence of 2 equiv of PPh3 at ambient temperature. Presumably, the electronic configuration of the neutral {Fe(NO)2}10 DNICs could be described as {Fe-2(NO+)2}10. According to HSAB rule, triphenylphosphine (compared to TMEDA and ethylenediamine) tends to be softer ligand favorably binding to {Fe(NO)2}10 motif. The neutral {Fe(NO)2}10 complex 5 can be generated from reaction of the neutral {Fe(NO)2}10 complex 4 with 1 equiv of ethylenediamine ligand. The driving force of the ligand substitution reaction might be due to the fact that the steric hindrance of ethylenediamine ligand is less than TMEDA.
The biomimetic [2Fe-2S] cluster [PPN]2[(S(CH2)nS)Fe(μ-S)2Fe(S(CH2)nS)] (n
= 2(7), 3(8), 4(9), 6(10)) were synthesized by reaction of [PPN]2[S5Fe(μ-S)2FeS5] (6) and 2 equiv of different chain-length thiolates and 8 equiv of thiol. Compared to the other [PPN]2[(S(CH2)nS)Fe(μ-S)2Fe(S(CH2)nS)] (n = 2, 3, 4, 6), complex [PPN]2[(S(CH2)6S)Fe(μ-S)2Fe(S(CH2)6S)] is the most stable. The bidentate alkyl DNICs (( n = 2(11), 3(12), 4(13), 6(14)) are synthesized from either reaction of complex 7, 8, 9 and 10 with PPh3 and NO(g) or the reaction of cationic [(sparteine)Fe(NO)2]+ (16) (the complex 16 was synthesized by adding one equiv of oxidant agent [NO][BF4] to the complex 15) with 1 equiv of [S(CH2)nS]2–. RRE [Fe2(μ-SPh)2(NO)4] (17) could be synthesized by reaction of complex 1 and complex 16 serving as {Fe(NO)2}9-donor reagent. Complexes 2, 8, 12, 15 were characterized by IR, UV-vis, and single-crystal X-ray diffraction.
The presence of the anionic {Fe(NO)2}9 [(Cl)(p-FPhO)(Fe(NO)2]- (21)、
[(p-FPhO)2(Fe(NO)2]- (26) and [(OPh)2Fe(NO)2]- (23) implicated the possible existence of the protein-bound tyrosine-coordinate DNICs. Reaction of [Fe(Cl)3(NO)]- with 3 equiv of [Na][p-FOPh] led to the formation of complex 21. Reaction of complex 21 with [Na][NO2] and [Na][p-FOPh] gives rise to complex 26. It is presumed that the better binding ability between [Na]+ and [Cl]- promotes the formation of intermediate [(NO2)(p-FOPh)Fe(NO)2]-. Addition of theσ-donor and π-donor [Na][p-FOPh] ligand triggers the ligand substitution reaction of [(NO2)(p-FOPh)Fe(NO)2]- yielding the complex 26. The synthetic process of the complex 23 is similar to that of complex 26. Addition of the strong electron-donating thiolate groups such as [SPh]- and [-SC4H3S]- to complex 23 led to the formation of [(OPh)(SPh)FeNO)2]- (27) and [(OPh)(-SC4H3S)Fe(NO)2]- (28), respectively. However, addition of the strongσ-donor and π-donor [C3H3N2]- ligand to complex 23 in 1:1 and 1:2 via ligand substitution led to the formation of complex [(OPh)(C3H3N2)FeNO)2]- (25) and [(C3H3N2)2FeNO)2]- (29), respectively. EPR spectrum of complexes 21, 23, 26, 27,and 28 exhibit the well-resolved five-line EPR signal, and complexes 25and 29 exhibit the well-resolved nine-line EPR signal at gav = 2.03 ± 0.004. Compared to the thermodynamical stability of the series of complexes 1, 23, 25, 27, 29, [(SPh)(C3H3N2)Fe(NO)2]- and [(NO2)2Fe(NO)2]-, this study shows that complex 1 is the most thermodynamically stable, followed by complexes [(SPh)(C3H3N2)Fe(NO)2]-、29、27、25、23 and complex [(NO2)2Fe(NO)2]- (22). Complexes 21, 23, 26, 27 and 28 were characterized by IR, UV-vis, and single-crystal X-ray diffraction. On the basis of the electron-donating ability, we can conclude that the bond distance decreases in the trend of Fe-Se, Fe-S, and Fe-O from the X-ray data of complexes 1, 23, 26 and [(SePh)2Fe(NO)2]-. The separation in NO stretching frequency (△νNO is 65 cm-1, 45 cm-1, and 55 cm-1) could be used to distinguish the O/Cl, O/O or N/O ligation modes of complexes 21, 23, 25 and 26； S/S or Se/Se coordinated to {Fe(NO)2}9 core of complex 1/[(SePh)2Fe(NO)2]-； and the S/O coordination of complexes 27/28.

並列關鍵字

Nitric Oxide ； Dinitrosyl iron complex ； Stability of model complex ； reactivity of model complex ； Interconversion of model complex

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