Li Fei, Wang Mei, Ma Chengbing, Gao Aiping, Chen Hongbo, Sun Licheng
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Zhongshan Road 158-46, Dalian, 116012, China.
Dalton Trans. 2006 May 28(20):2427-34. doi: 10.1039/b516697g. Epub 2006 Mar 15.
Three mononuclear iron complexes and one binuclear iron complex, [Fe(tpoen)Cl].0.5(Fe2OCl6) (1), [Fe(tpoen)Cl]PF6 (2), Fe(tpoen)Cl3 (3) and [Fe(tpoen)]2(mu-O)4 (4) (tpoen = N-(2-pyridylmethoxyethyl)-N,N-bis(2-pyridylmethyl)amine), were synthesized as functional models of non-heme iron oxygenases. Crystallographic studies revealed that the Fe(II) center of 1 is in a pseudooctahedral environment with a pentadentate N4O ligand and a chloride ion trans to the oxygen atom. The Fe(III) center of 3 is ligated by three nitrogen atoms of tpoen and three chloride ions in a facial configuration. Each Fe(III) center of 4 is coordinated with four nitrogen atoms and an oxygen atom of tpoen with the Fe-O-Fe angle of 172.0(3) angstroms. Complexes 2, 3 and 4 catalysed the oxidation of cyclohexane with H2O2 in the total TNs of 24-36 with A/K ratios of 1.9-2.4. Under the same conditions they also catalysed both the oxidation of ethylbenzene to benzylic alcohol and acetobenzene with good activity (30-47 TN) and low selectivity (A/K 0.7), and the oxidation of adamantane with moderate activity (15-18 TN) and low regioselectivity (3 degrees/2 degrees 3.0-3.2). With mCPBA as oxidant the catalytic activities of 2, 3 and 4 increased 1.8 to 2.3-fold for the oxidation of cyclohexane and ethylbenzene and 6.3 to 7.5-fold for the oxidation of adamantane. Drastic enhancement of the regioselectivity was observed in the oxidation of adamantane (3 degrees/2 degrees 18.5-30.3).
合成了三种单核铁配合物和一种双核铁配合物，即[Fe(tpoen)Cl]·0.5(Fe2OCl6) (1)、[Fe(tpoen)Cl]PF6 (2)、Fe(tpoen)Cl3 (3) 和 [Fe(tpoen)]2(μ-O)4 (4)（tpoen = N-(2-吡啶基甲氧基乙基)-N,N-双(2-吡啶基甲基)胺），作为非血红素铁加氧酶的功能模型。晶体学研究表明，1 的 Fe(II) 中心处于一个伪八面体环境中，有一个五齿 N4O 配体，且一个氯离子与氧原子处于反位。3 的 Fe(III) 中心由 tpoen 的三个氮原子和三个氯离子以面式构型配位。4 的每个 Fe(III) 中心与 tpoen 的四个氮原子和一个氧原子配位，Fe-O-Fe 角为 172.0(3) 埃。配合物 2、3 和 4 以 H2O2 催化环己烷氧化，总转化数为 24 - 36，A/K 比为 1.9 - 2.4。在相同条件下，它们还能以良好的活性（30 - 47 转化数）和低选择性（A/K 0.7）催化乙苯氧化为苄醇以及苯乙酮氧化，并且能以中等活性（15 - 18 转化数）和低区域选择性（叔碳/仲碳 3.0 - 3.2）催化金刚烷氧化。以间氯过氧苯甲酸作为氧化剂时，2、3 和 4 对环己烷和乙苯氧化的催化活性提高了 1.8 至 2.3 倍，对金刚烷氧化的催化活性提高了 6.3 至 7.5 倍。在金刚烷氧化中观察到区域选择性大幅提高（叔碳/仲碳 18.5 - 30.3）。
