Diiron(III) complexes of tridentate 3N ligands as functional models for methane monooxygenases: Effect of the capping ligand on hydroxylation of alkanes
Diiron(III) complexes of tridentate 3N ligands as functional models for methane monooxygenases: Effect of the capping ligand on hydroxylation of alkanes
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DOI：
10.1016/j.poly.2013.08.067
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发表时间：
2014-01
期刊：
影响因子：
2.6
通讯作者：
M. Sankaralingam;M. Palaniandavar
中科院分区：
文献类型：
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作者：
M. Sankaralingam;M. Palaniandavar
一系列非血红素（μ-氧代）双[Fe_2（O）（OBz）_2（L）_2]~（2+）（1-6）型（μ-苯甲酸根）桥联二铁（III）配合物，其中OBz =苯甲酸根，L =二（吡啶-2-基甲基）胺（L1），（（6-甲基吡啶-2-基-）甲基）（吡啶-2-基）甲胺（L2），N，N-二甲基-N '-（吡啶-2-基甲基）乙二胺（L3），（1-甲基-1H-咪唑-2-基）-N-（吡啶-2-基甲基）-甲胺（L4），（1H-苯并[o]咪唑-2-基）-N-（吡啶-2-基甲基）甲胺（L5）和双（吡啶-2-基甲基）甲胺（L5）（1H-苯并[o]咪唑-2-基）甲基）胺（L 6）的结构经元素分析、光谱和电化学方法表征。研究了它们作为间氯过苯甲酸（m-CPBA）选择性羟基化反应的催化剂。在乙腈/二氯甲烷的混合溶剂中，所有的配合物显示的d-d带特征的三重桥连二铁（III）的核心，揭示了它们在溶液中保留其身份。当封端配体上的给体原子被更强的给体取代时，单电子FeIIIFeIII→ FeIIIFeII还原的E1/2值变得更负。所有配合物都是环己烷羟基化的有效催化剂，总转化数为390-410，醇选择性好（A/K，9.3-12.8）。金刚烷被选择性氧化（3°/2°，15.7-28.1）为1-金刚烷醇和2-金刚烷醇，沿着少量2-金刚烷酮（Total TON，336-437），有趣的是，在二铁（III）中心周围具有吡啶基供体的3 N封端配体导致高3°/2°键选择性。
A series of non-heme (μ-oxo)bis(μ-benzoato)-bridged diiron(III) complexes of the type [Fe2(O)(OBz)2(L)2]2+(1–6), where OBz = benzoate, L = bis(pyridin-2-ylmethyl)amine (L1),N-((6-methylpyridin-2-yl-)methyl)(pyridin-2-yl)methanamine (L2),N,N-dimethyl-N′-(pyrid-2-ylmethyl)ethylenediamine (L3), (1-methyl-1H-imidazol-2-yl)-N-(pyridin-2-ylmethyl)-methanamine (L4), (1H-benzo[o]imidazol-2-yl)-N-(pyridin-2-ylmethyl)methanamine (L5) and bis((1H-benzo[o]imidazol-2-yl)methyl)amine (L6), have been isolated and characterized by means of elemental analysis, spectral and electrochemical methods. They have been studied as catalysts for selective hydroxylation of alkanes usingm-choloroperbenzoic acid (m-CPBA) as the oxidant. In acetonitrile/dichloromethane mixed solvent all the complexes display a d–d band characteristic of a triply bridged diiron(III) core, revealing that they retain their identity in solution. Upon replacing a donor atom on the capping ligand by a stronger donor, theE1/2value of the one-electron FeIIIFeIII→ FeIIIFeIIreduction becomes more negative. All the complexes function as efficient catalysts for hydroxylation of cyclohexane, with 390–410 total turnover numbers and good alcohol selectivity (A/K, 9.3–12.8). Adamantane is selectively oxidized (3°/2°, 15.7–28.1) to 1-adamantanol and 2-adamantanol, along with a small amount of 2-adamantanone (Total TON, 336–437), and interestingly the 3N capping ligands with the pyridyl donor around the diiron(III) center lead to high 3°/2° bond selectivity.