三氮二氧配位基鈷金屬超氧錯合物之反應性探討

Abstract

本研究使用參考文獻(Tetrahedron: Asymmetry 2004, 15, 177.)之三氮二氧五牙基(簡稱H2BDPP)，合成二價鈷錯合物CoII(BDPP)(1)，本實驗室王俊傑學長經研究證實，此二價鈷錯合物於低溫下有活化氧氣的反應性，經過實驗驗證可以得到CoIII(BDPP)(O2)(2)，並且得知CoIII(BDPP)(O2)(2) 可以對較弱的氫氧鍵受質進行奪氫反應，例如 : TEMPO-H、azadol，得到 CoIII(BDPP)(OOH)。本研究則針對CoIII(BDPP)(O2)(2) 的質子化以及質子化後還原的過程進行研究，將CoIII(BDPP)(O2)(2) 質子化後可以得到在 -90⁰C 穩定的質子化中間體CoIII(BDPP)(O2)(H+)(C₂HF₃O₂-)(3) / CoIII(BDPP)(O2)(H+)( OTf-)(3')，並透過UV-Vis 光譜、EPR光譜、rRaman光譜鑑定此中間體的性質，將CoIII(BDPP)(O2)(H+)( OTf -)(3') 在 -120 ⁰C 加上還原劑加以還原，可以在UV-Vis光譜上發現類似CoIII(BDPP)(OOH) 的訊號，推測可能有 CoIII(BDPP)(OOH) 的生成。於此同時也以兩種路易士酸 Sc(OTf)3 、 B(C6F5)3 作為質子類比試劑，與CoIII(BDPP)(O2)(2)反應後可觀測到與質子光譜相同的UV-Vis光譜以及相同的EPR 光譜，將 CoIII(BDPP)(O2)(Sc3+)(OTf-)3(4) ，在 – 90 ⁰C 下再加入還原劑，可以在UV-Vis光譜上觀察到類似CoIII(BDPP)(OOH)的光譜訊號，推測產物為CoIII(BDPP)(OOSc)2+。透過此研究，可以了解超氧化物經質子化的性質變化，以及質子化後的還原反應機制。In previous study, N3O2 pentadentate ligand H2BDPP, published on Tetrahedron(Tetrahedron: Asymmetry 2004, 15, 177.), was deprotonated and employed to react with CoCl2 to form a CoII(BDPP)(1) complex. Senior researcher Chun-Chieh Wang had found that CoII(BDPP)(1) could react with dioxygen and formed CoIIIBDPP(O2)(2) intermediate only under low temperature . CoIIIBDPP(O2)(2) was well-characterized by UV-Vis spectrum, EPR spectrum and rRaman spectrum. CoIIIBDPP(O2)(2) was found to be able to conduct HAT with substrates with weak O-H bond, like TEMPO-H, Azadol, and formed the bio-relative intermediate CoIIIBDPP(OOH). CoIIIBDPP(OOH) was crystallized under -20⁰C and well-characterized by UV-Vis spectrum, rRaman spectrum and XRD. To understand the reactivity of superoxide, especially the protonation and electron transfer process. We protonated CoIIIBDPP(O2)(2) and got a low-temp stable intermediate. The protonated superoxo, CoIII(BDPP)(O2)(H+)(C₂HF₃O₂-)(3) / CoIII(BDPP)(O2)(H+)(OTf-)(3') was well-characterized by UV-Vis spectrum, EPR spectrum and rRaman spectrum. When CoIII(BDPP)(O2)(H+)(OTf-)(3') was reacted with decamethylferrocene under -120 ⁰C , we could get a UV-Vis spectrum was similar to CoIII(BDPP)(OOH). In addition, we took two Lewis Acids, Sc(OTf)3, B(C6F5)3 , as analogues of proton. We could get almost identical UV-Vis signals and EPR signals with the protonated one after CoIIIBDPP(O2)(2) was reacted with Sc(OTf)3 and B(C6F5)3. The reaction with Sc(OTf)3 was further reduced by decamethylferrocene under -90 ⁰C. The UV-Vis spectrum shared two feature peaks with CoIII(BDPP)(OOH). The hypothetical CoIIIBDPP(OOSc)2+ was likely formed. Through this study, we believed to establish a new cobalt superoxo model to understand the protonation and electron transfer process which was still rare in bioinorganic region.