六配位三價鈷超氧錯合物之合成與反應性

Abstract

本研究參考王俊傑學長在2016年所發表的二價鈷金屬錯合物Co(BDPP)，將其配位基修飾成H2BDPtBuP，並合成出二價鈷錯合物Co(BDPtBuP) (1)，且進行鑑定及反應性探討。錯合物1與氧氣反應可形成三價鈷超氧化物Co(BDPtBuP)(O2˙) (2)，將其與強酸HOTf進行質子轉移反應，形成[Co(HBDPtBuP)(O2˙)](OTf)。若與具較弱O-H鍵的受質TEMPOH反應，會形成Co(BDPtBuP)(OOH) (3)。另外，可藉由TEA進行反滴定反應所求得pKa值和從循環伏安法得到的還原電位E1/2，使用 Bordwell方程式可求出錯合物3的OO-H鍵能。利用錯合物2與不同O-H鍵能的酚類反應，可觀察到大部分酚類只與錯合物2產生氫鍵作用力。而與對硝基苯酚反應會行質子轉移反應形成[Co(HBDPtBuP)(O2˙)]+。

In this study, a CoII complex, Co(BDPtBuP) (1), was synthesized by employing a new pentadentate ligand, H2BDPtBuP, modified from the previous reported H2BDPP ligand. Complex 1 was fully characterized and investigated regarding their reactivity. The reaction of 1 with dioxygen producted a CoIII superoxo complex, Co(BDPtBuP)(O2˙) (2), The reaction of 2 with the strong acid HOTf formed [Co(HBDPtBuP)(O2˙)](OTf). If complex 1 reacted with TEMPOH, which possessing a weaker O-H bond, resulting in a CoIII-hydroperoxo complex, Co(BDPtBuP)(OOH) (3). In addition, the reduction potential E1/2 obtained from cyclic voltammetry and the pKa value of the protonated 2 acquired by back titration with TEA allowed us to calculated the OO-H bond energy of 3 using the Bordwell’s equation.The reactions of 2 with phenols having different O-H bond energies reveal that most of phenols only have hydrogen bonding interaction with complex 2. In contrast, the reaction of 2 with p-nitrophenol proceeded a proton transfer reaction, to from [Co(HBDPtBuP)(O2˙)]+.