Hori Yuta, Shiota Yoshihito, Tsuji Tomokazu, Kodera Masahito, Yoshizawa Kazunari
Institute for Materials Chemistry and Engineering and IRCCS, Kyushu University , Fukuoka 819-0395, Japan.
Department of Molecular Chemistry and Biochemistry, Doshisha University , Kyotanabe, Kyoto 610-0321, Japan.
Inorg Chem. 2018 Jan 2;57(1):8-11. doi: 10.1021/acs.inorgchem.7b02563. Epub 2017 Dec 16.
A dicopper(II) complex, [Cu(μ-OH)(6-hpa)], where 6-hpa is 1,2-bis[2-[bis(2-pyridylmethyl)aminomethyl]-6-pyridyl]ethane, generates an oxyl radical of CuO and catalyzes the selective hydroxylation of benzene to phenol. From the structural similarity to methane activation catalysts (e.g., bare CuO ion, Cu-ZSM-5, and particulate methane monooxygenase), it is expected to catalyze methane hydroxylation. The catalytic performance for the hydroxylation of methane to methanol by this dicopper complex is investigated by using density functional theory (DFT) calculations. The whole reaction of the methane conversion involves two steps without radical species: (1) C-H bond dissociation of methane by the CuO moiety and (2) C-O bond formation with methyl migration. In the first step, the activation barrier is calculated to be 10.2 kcal/mol, which is low enough for reactions taking place under normal conditions. The activation barrier by the other CuO moiety is higher than that by the CuO moiety, which should work to turn the next catalytic cycle. DFT calculations show that the dicopper complex has a precondition to hydroxylate methane to methanol. Experimental verification is required to look in detail at the reactivity of this dicopper complex.
一种二铜（II）配合物[Cu(μ-OH)(6-hpa)]，其中6-hpa为1,2-双[2-[双(2-吡啶甲基)氨基甲基]-6-吡啶基]乙烷，可生成CuO的氧自由基，并催化苯选择性羟基化为苯酚。从与甲烷活化催化剂（如裸露的CuO离子、Cu-ZSM-5和颗粒状甲烷单加氧酶）的结构相似性来看，预计它能催化甲烷羟基化。通过密度泛函理论（DFT）计算研究了这种二铜配合物将甲烷羟基化为甲醇的催化性能。甲烷转化的整个反应包括两个无自由基物种的步骤：（1）甲烷的C-H键通过CuO部分解离，（2）伴随甲基迁移的C-O键形成。在第一步中，计算出的活化能垒为10.2千卡/摩尔，这对于在正常条件下发生的反应来说足够低。另一个CuO部分的活化能垒高于该CuO部分的活化能垒，后者应作用于开启下一个催化循环。DFT计算表明，二铜配合物具有将甲烷羟基化为甲醇的前提条件。需要进行实验验证以详细研究这种二铜配合物的反应活性。
