Non-heme lron(II) complexes containing tripodal tetradentate nitrogen ligands and their application in alkane oxidation catalysis
Non-heme lron(II) complexes containing tripodal tetradentate nitrogen ligands and their application in alkane oxidation catalysis
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DOI：
10.1021/ic0509229
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发表时间：
2005-10-31
影响因子：
4.6
通讯作者：
White, AJP
中科院分区：
文献类型：
--
作者：
Britovsek, GJP;England, J;White, AJP
一系列的铁（II）含有三足四齿氮配体与[N（CH（2）Pyr）（3-n）]型吡啶和二甲胺供体的（三氟甲磺酸酯）配合物（CH2CH2NMe2）（n）] [n = 0（tpa，1），n = 1（iso-bpmen，3），n = 2（Me-4-benpa，4），n = 3（Me-6-tren，5）]和线型四齿配体[（CH（2）Pyr）MeN（CH_2CH_2）NMe（CH（2）Pyr），（bpmen，2）]。这些配合物在固态和二氯甲烷溶液中的优选的配位几何形状从6到5以1到5的顺序变化。在乙腈中，所有配合物的三氟甲磺酸酯配体都容易被乙腈配体取代。配合物[Fe（1）（CH 3CN）（2）]（2+）在室温下基本上是低自旋的，而具有较少吡啶供体的配体增加了对高自旋Fe（II）的偏好。吡啶供体的数量和金属中心的自旋状态都强烈影响400 nm附近的特征MLCT带的强度。以环己烷为底物，考察了配合物对烷烃氧化的催化性能。含配体1-3的配合物是活性更高、选择性更好的催化剂，可能是通过金属氧化机理进行的，而含配体4和5的配合物则产生Fenton型化学反应。
A series of iron(II) bis(triflate) complexes containing tripodal tetradentate nitrogen ligands with pyridine and dimethylamine donors of the type [N(CH(2)Pyr)(3-n)(CH2CH2NMe2)(n)] [n = 0 (tpa, 1), n = 1 (iso-bpmen, 3), n = 2 (Me-4-benpa, 4), n = 3 (Me-6-tren, 5)] and the linear tetradentate ligand [(CH(2)Pyr)MeN(CH2CH2)NMe(CH(2)Pyr), (bpmen, 2)] has been prepared. The preferred coordination geometry of these complexes in the solid state and in CH2Cl2 solution changes from six- to five-coordinate in the order from 1 to 5. In acetonitrile, the triflate ligands of all complexes are readily displaced by acetonitrile ligands. The complex [Fe(1)(CH3CN)(2)](2+) is essentially low spin at room temperature, whereas ligands with fewer pyridine donors increase the preference for high-spin Fe(II). Both the number of pyridine donors and the spin state of the metal center strongly affect the intensity of a characteristic MLCT band around 400 nm. The catalytic properties of the complexes for the oxidation of alkanes have been evaluated, using cyclohexane as the substrate, Complexes containing ligands 1-3 are more active and selective catalysts, possibly operating via a metal-based oxidation mechanism, whereas complexes containing ligands 4 and 5 give rise to Fenton-type chemistry.