Physicochemical Properties of Mn- and Cr-Corrole Intermediates, and Reversible Conversion between Metal-Oxo and Metal Peroxo Species via O-O Bond Cleavage and Formation

Abstract

고(高)-산화가의 망간-옥소 중간체는 히드록시 이온(OH-)의 친핵성 반응으로 산소-산소 결합을 형성하는 활성 종이라고 알려져 왔다. 그리고 산소-산소 결합을 형성하는 반응의 메커니즘은 산소-산소 결합이 끊어지는 반응과정과 유사할 것이라고 예상된다. 이 연구는 망간-코롤 (Mn-corrole) 을 사용하여 가역적인 산소간 결합과 끊어짐 반응을 보여준다. 망간 코롤 화합물, Mn(III)(TFMPC) (TFMPC = 5,10,15-tris(3,5-trifluoromethylphenyl)corrolato trianion),을 시작 물질로 하여 망간(IV)-퍼옥소와 망간(V)-옥소 코롤 중간체들을 각각 생성하고, UV-vis, EPR, ESI-MS 그리고 resonance Raman 등의 다양한 분광학적 방법으로 망간(IV)-퍼옥소와 망간(V)-옥소 종의 성질을 규명하였다. 또한, 망간(IV)-퍼옥소에 산을 첨가하면 망간(V)-옥소가 생성되고, 반대로 망간(V)-옥소에 염기를 첨가하면 망간(IV)-퍼옥소가 생성되는 것을 확인했다. 산과 염기를 첨가할 때 보이는 가역적인 상호전환반응은 이 중간체들이 산소-산소 결합 형성과 결합 끊어짐 과정에 직접적으로 사용된다는 것을 보여준다.;Manganese(V)-oxo intermediate has been implicated as an active species for the O-O bond formation via nucleophilic attack of OH?C onto high-valent manganese(V)-oxo species. Even more, it has been presumed that O-O bond cleavage and formation would occur through similar mechanistic way. Here we present the first example of reversible O-O bond cleavage and formation by manganese corroles. Mn(IV)-peroxo and Mn(V)-oxo corroles were prepared independently by reacting Mn(III)(TFMPC) (TFMPC = 5,10,15-tris(3,5-trifluoromethylphenyl)corrolato trianion) as a starting material with H2O2/base and PhIO as an oxidant, respectively. These Mn(IV)-peroxo and Mn(V)-oxo species were extensively characterized with various spectroscopic techniques, such as UV-vis, EPR, ESI-MS and resonance Raman. The intermediates were directly used in O-O bond cleavage and formation reactions. Remarkably, a reversible conversion between the Mn(IV)-peroxo and Mn(V)-oxo corroles via O-O bond cleavage and formation was observed upon addition of acid and base. Cr(V)-oxo corrole intermediate was also synthesized and well characterized with various spectroscopic methods. Spectroelectrochemical property of Cr(V)-oxo species was investigated. The reactivities of Cr(V)-oxo corrole with triply bonded CrV∇O moiety have been poorly investigated due to the low oxidizing power. Therefore, reactivity of Cr(V)-oxo corrole complex was investigated in oxygen atom transfer reaction, such as phosphine oxidation and in hydride transfer reaction in the absence and presence of redox-inactive metal ion such as Sc3+ in the anaerobic conditions. We also found that the reversible conversion between Cr(V)-oxo corrole and new Cr(IV)-corrole intermediate by adding acid and base.