非血基質酵素之N3O2五牙配位基二價鐵擬態化合物之合成、性質及反應性探討
Abstract
本研究沿用之前所設計的N3O2五牙配位基H2BDPP，為一個 C2對稱並具有掌性中心與羥基的吡咯啶。將去質子化的配位基BDPP2-與FeCl2反應，能成功地得到二價鐵錯合物FeIIBDPP (1)，若於室溫下將[Fe(CH3CN)6](OTf)2與BDPP2-反應並加入氧氣可得到三價鐵錯合物[FeIIIBDPP](OTf) (2)。錯合物1、2也藉由X-ray單晶繞射解析法、紫外光-可見光光譜儀(UV/vis)、循環伏安法(CV) 以及電子順磁共振光譜(EPR)進行鑑定與探討。錯合物1與氧氣於-80˚C下反應時，溶液呈現茶色且在UV/vis圖譜上可以觀察到330 nm的特徵吸收峰，當溫度升至-50˚C，可以觀察到溶液呈紫色，且具有330 nm、525 nm 兩個特徵吸收峰，與文獻中FeIII-OOH相似，最後，於0˚C時可得到黃色溶液，與錯合物2有相似的UV/vis特徵吸收峰(λmax = 310 nm)，而反應後的溶液可由氣相層析-質譜儀(GC-MS)偵測到二苯基甲酮的產生。若以三苯基磷為反應物，於-80˚C下與氧氣反應後的錯合物1溶液反應，可由GC-MS偵測到主產物三苯基氧化磷(33%) 以及副產物二苯基甲酮(12%)。我們預測二苯基甲酮的生成應該是反應中進行了BDPP2-上的氫原子轉移並伴隨著碳-碳鍵的斷裂。
A previously synthesized C2-symmetric N3O2 pentadentate ligand, H2BDPP, containing two hydroxyl group attached pyrrolidines, was employed in this study. The mononuclear FeII complex, Fe(BDPP) (1), was successfully synthesized from the reaction of FeCl2 with deprotonated ligand, BDPP2-. Reaction of [Fe(CH3CN)6](OTf)2 with BDPP2- in the presence of dioxygen gave a FeIII complex, [FeBDPP](OTf) (2), at ambient temperature. Complexes 1 and 2 were characterized by X-ray crystallography, cyclic voltammetry, UV/vis and EPR spectroscopies. Reaction of complex 1 with dioxygen at -80 ˚C resulted in a pale brown species with an absorption at 330 nm. As the temperature of the reaction solution rose to -50 ˚C, the purple species was observed with an electronic absorption spectrum (λmax = 320, 525 nm) similar to that of FeIII-OOH. Finally, a yellow FeIII species was obtained at 0 ˚C, whose UV/vis pattern was similar to that of complex 2. Importantly, benzophenone was observed from the resulting solution at ambient temperature and determined by GC-MS. When triphenylphosphine was applied as a substrate to the dioxygen-bubbled solution of complex 1, triphenylphosphine oxide (33% yield) was produced as a major product and benzophenone (12% yield) was also observed as a side-product. Formation of benzophenone was suspected as a result of the hydrogen atom abstraction accompanying the C-C bond cleavage of BDPP2-.
A previously synthesized C2-symmetric N3O2 pentadentate ligand, H2BDPP, containing two hydroxyl group attached pyrrolidines, was employed in this study. The mononuclear FeII complex, Fe(BDPP) (1), was successfully synthesized from the reaction of FeCl2 with deprotonated ligand, BDPP2-. Reaction of [Fe(CH3CN)6](OTf)2 with BDPP2- in the presence of dioxygen gave a FeIII complex, [FeBDPP](OTf) (2), at ambient temperature. Complexes 1 and 2 were characterized by X-ray crystallography, cyclic voltammetry, UV/vis and EPR spectroscopies. Reaction of complex 1 with dioxygen at -80 ˚C resulted in a pale brown species with an absorption at 330 nm. As the temperature of the reaction solution rose to -50 ˚C, the purple species was observed with an electronic absorption spectrum (λmax = 320, 525 nm) similar to that of FeIII-OOH. Finally, a yellow FeIII species was obtained at 0 ˚C, whose UV/vis pattern was similar to that of complex 2. Importantly, benzophenone was observed from the resulting solution at ambient temperature and determined by GC-MS. When triphenylphosphine was applied as a substrate to the dioxygen-bubbled solution of complex 1, triphenylphosphine oxide (33% yield) was produced as a major product and benzophenone (12% yield) was also observed as a side-product. Formation of benzophenone was suspected as a result of the hydrogen atom abstraction accompanying the C-C bond cleavage of BDPP2-.
Description
Keywords
氧氣, 三苯基磷, 三苯基氧化磷, dioxygen, triphenylphosphine, triphenylphosphine oxide