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首页> 外文期刊>Chemistry: A European journal >Highly effective water oxidation catalysis with iridium complexes through the use of NaIO_4
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Highly effective water oxidation catalysis with iridium complexes through the use of NaIO_4

机译：通过使用NaIO_4与铱配合物进行高效的水氧化催化

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Exceptional water oxidation (WO) turnover frequencies (TOF=17 000h ~(-1)), and turnover numbers (TONs) close to 400 000, the largest ever reported for a metal-catalyzed WO reaction, have been found by using [Cp*Ir~(III)(NHC)Cl_2] (in which NHC=3-methyl-1-(1- phenylethyl)-imidazoline-2-ylidene) as the pre-catalyst and NaIO_4 as oxidant in water at 40 °C. The apparent TOF for [Cp*Ir III(NHC)X2] (1 X, in which X stands for I (1 I), Cl (1 Cl), or triflate anion (1 OTf)) and [(Cp*-NHCMe)IrIIII 2] (2) complexes, is kept constant during almost all of the O _2 evolution reaction when using NaIO4 as oxidant. The TOF was found to be dependent on the ligand and on the anion (TOF ranging from ≈600 to ≈1100h-1 at 25 °C). Degradation of the complexes by oxidation of the organic ligands upon reaction with NaIO4 has been investigated. 1HNMR, ESI-MS, and dynamic light-scattering measurements (DLS) of the reaction medium indicated that the complex undergoes rapid degradation, even at low equivalents of oxidant, but this process takes place without formation of nanoparticles. Remarkably, three-month-old solution samples of oxidized pre-catalysts remain equally as active as freshly prepared solutions. A UV/Vis feature band at λmax=405nm is observed in catalytic reaction solutions only when O_2 evolves, which may be attributed to a resting state iridium speciation, most probably Ir-oxo species with an oxidation state higher than IV.
机译：通过使用[Cp]，发现了异常的水氧化（WO）周转频率（TOF = 17 000h〜（-1））和接近400,000的周转数（TONs），这是有史以来最大的金属催化的WO反应。 * Ir〜（III）（NHC）Cl_2]（其中NHC = 3-甲基-1-（1-苯乙基）-咪唑啉-2-亚烷基）作为前催化剂，NaIO_4作为氧化剂在40°C的水中。 [Cp * Ir III（NHC）X2]的表观TOF（其中X代表I（1 I），Cl（1 Cl）或三氟甲磺酸根阴离子（1 OTf））和[（Cp * -NHCMe ）IrIIII 2]（2）配合物在使用NaIO4作氧化剂时几乎在所有O _2析出反应中均保持恒定。发现TOF取决于配体和阴离子（在25°C时TOF范围从≈600到≈1100h-1）。已经研究了在与NaIO 4反应时通过有机配体的氧化来降解复合物。反应介质的1 HNMR，ESI-MS和动态光散射测量（DLS）表明，即使在氧化剂当量较低的情况下，配合物也会快速降解，但是该过程不会形成纳米颗粒。值得注意的是，三个月大的氧化前催化剂溶液样品的活性与刚制备的溶液相同。仅当O_2放出时，才在催化反应溶液中观察到λmax= 405nm处的UV / Vis特征带，这可能归因于铱态的静止态，最有可能是氧化态高于IV的Ir-氧代物种。

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