金屬蛋白在生物體中可以當成一氧化氮(NO)的儲存池，像是血紅蛋白和亞硝酸還原酶。在缺氧的情況下，脫氧的血紅蛋白可以接上亞硝酸鹽並促使亞硝酸鹽還原產生一氧化氮。一氧化氮可以提高血液和氧氣的結合率。不過確切的反應機制到現在依然沒有被確定。為了想要瞭解金屬蛋白如何進行，我們藉由[FeIII(PS3”)(CH3CN)] (1) 和 NBu4NO2反應去合成FeIII-NO2-的錯合物， [NBu4][FeIII(PS3”)(NO2)] (2)。 重要的是，錯合物2與TEMPOH的反應可以產生{FeNO}7的物種，[Fe(PS3”)(NO)] (3的陰離子)。亞硝酸根透過氫原子抓取還原成硝酸根。相反地，錯合物2和酸反應產生一個五配位的{FeNO}6物種，[Fe(PS3”)(NO)] (4)。錯合物1-4藉由X-ray晶體學和數種光譜學鑑定。
此外，[PPh4][FeIII(PS3”)(O2)] (5)和數種酸的反應也被探討。錯合物5先前被我們實驗室發表過是一個side-on的Fe(III)-O2-物種。在-85oC下加入不同質子來源到5的THF溶液，產生一個沒有EPR訊號的紫色中間體，被推測是Fe(IV)-OOH物種，[FeIV(PS3”)(OOH)]。這個紫色的溶液僅能穩定幾秒鐘然後快速變成另一個紅棕色的中間體，這個中間體有S = 1/2的EPR訊號。不幸的是，企圖去分離出這些亞穩狀態的物種最後還是失敗了。

Metalloproteins such as hemoglobin (Hb) and nitrite reductase (NiR), could act as reservoirs for nitric oxide (NO) in vivo. Under hypoxic conditions, deoxygenated hemoglobin (deoxyHb) is able to bind nitrite and promote nitrite reduction to generate nitric oxide. Nitric oxide could enhance oxygenation in blood. However, the detail mechanism of nitrite reduction in metalloproteins is still not well-defined. In order to understand how metalloproteins proceed nitrite reduction, at this work, we synthesized an Fe(III)-NO2- complex, [NBu4][FeIII(PS3”)(NO2)] (2), by treating [FeIII(PS3”)(CH3CN)] (1) with NBu4NO2 (PS3”3- = P(C6H3-3-SiMe3-2-S)33-). Importantly, the reaction of complex 2 with TEMPOH (TEMPOH=2,2,6,6-tetramethylpiperidine-1-oxyl) generated an {FeNO}7 species, [Fe(PS3”)(NO)]- (anion of 3). The bound nitrito group was reduced to a nitrosyl group via a hydrogen atom abstraction from TEMPOH. In contrast, complex 2 reacting with acid yielded a five-coordinate {FeNO}6 species, [Fe(PS3”)(NO)] (4). Complexes 1-4 were well characterized by X-ray crystallography and various spectroscopies.
In addition, the reaction of [PPh4][FeIII(PS3”)(O2)] (5) with various acid was explored at this work. Complex 5 previously reported by our laboratory is a side-on Fe(III)-O2- species. Adding different proton source to a THF solution of 5 at -85oC resulted in an EPR-silent purple intermediate that is proposed as a Fe(IV)-hydroperoxo species, [FeIV(PS3”)(OOH)]. This purple solution is only stable for a few seconds and immediately changed to another red-brown intermediate that showed a S = 1/2 EPR signal. Unfortunately, attempts to isolate these metastable species ended in failure.

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