A Low-Spin Ruthenium(IV)-Oxo Complex: Does the Spin State Have an Impact on the Reactivity?
A Low-Spin Ruthenium(IV)-Oxo Complex: Does the Spin State Have an Impact on the Reactivity?
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DOI：
10.1002/anie.201002733
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发表时间：
2010-01-01
影响因子：
16.6
通讯作者：
Fukuzumi, Shunichi
中科院分区：
文献类型：
--
作者：
Kojima, Takahiko;Hirai, Yuichirou;Fukuzumi, Shunichi
高价金属氧合配合物是自然界和实验室中有机化合物氧化和加氧反应的关键活性物种。[1，2]虽然铁是高价金属氧代络合物中最常见的金属物种，[3]也有锰氧代，[4]铼氧代，[5]和其他金属氧代络合物。[6]高价金属-氧物种是通过分子氧的还原活化与质子转移偶联而产生的。[7-9]过氧化物如过氧化氢可以提供所谓的“过氧化物分流”以产生高价金属-氧代物质。[1-3]高价金属-氧代物种也可以通过质子耦合电子转移（PCET）产生，其中配位水分子的去质子化和金属中心的氧化协同发生。[10-14]高价金属-氧代物种的反应性根据金属的类型、金属中心的氧化态、配体和自旋状态而变化。理论研究表明，高价金属氧物种的反应活性可能是由两个相互靠近的自旋态决定的，这两个自旋态对与底物的反应具有不同的活化能垒。[15-17]阐明自旋状态对高价金属-氧代物种反应性的影响的最直接方法是检查具有不同自旋状态的类似系列金属-氧代络合物的反应性。已经有广泛的研究RuIV-氧代配合物，表现出三重态自旋状态（S= 1）。[18-20]然而，还没有RuIV-氧代络合物在基态表现出单重自旋态（S= 0）的实例。[21]因此，比较类似的高价金属氧物种与不同的自旋stations.We报告的反应性在这里的第一次RuIV-氧配合物与三（2-吡啶基甲基）胺（TPA）衍生物的自旋状态改变取决于类型的TPA衍生物。具有tpa衍生物的两种RuII-水络合物，四齿tpa和五齿N，N-双（2-吡啶甲基）-N-（6-羧酸-2-吡啶基-甲基）胺（6-COOH-tpa）单阴离子，[Ru-（tpa）（H2O）2] 2+（1）[13]和[Ru（6-COOH-tpa）（H_2O）]~+（2），通过（NH_4）_2 [Ce_（IV）（NO_3）_6]（CAN）的PCET反应转化为相应的RuIV-氧代配合物。我们得到了两种RuIV-氧代配合物，S= 1自旋态的[Ru（O）（tpa）（H_2O）]~（2+）（3）和S= 0自旋态的[Ru（O）（6-COOH-tpa）]~（4）。因此，具有不同自旋状态的类似RuIV-氧代配合物提供了一个极好的机会，根据它们的自旋状态来比较对底物的反应性。Ru II-水络合物2通过前体络合物[Ru（6-COOH-tpa）Cl] PF 6（参见图1）[22]与AgPF 6在水中通过脱氯反应制备，
High-valent metal–oxo complexes are key reactive species for oxidation and oxygenation of organic compounds in nature as well as in the laboratory.[1, 2] Although iron is the most common metal species among high-valent metal–oxo complexes,[3] there are also manganese–oxo,[4] ruthenium–oxo,[5] and other metal–oxo complexes.[6] High-valent metal–oxo species are produced by reductive activation of molecular oxygen coupled with proton transfer.[7–9] Peroxides such as hydrogen peroxide can provide a so-called “peroxide shunt” to produce high-valent metal–oxo species.[1–3] High-valent metal–oxo species can also be produced by proton-coupled electron transfer (PCET), in which deprotonation of a coordinated water molecule and oxidation of the metal center occur concertedly.[10–14] The reactivity of high-valent metal–oxo species varies depending on the type of metal, the oxidation state of the metal center, ligands, and the spin state. Theoretical studies proposed that the reactivity of high-valent metal–oxo species may be determined by two closely lying spin states, which have different activation barriers for the reactions with substrates.[15–17] The most straightforward way to clarify the effects of spin states on the reactivity of highvalent metal–oxo species is to examine the reactivity of an analogous series of metal–oxo complexes that have different spin states. There have been extensive studies on RuIV–oxo complexes that exhibit the triplet spin state (S= 1).[18–20] However, there has been no example of RuIV–oxo complexes exhibiting the singlet spin state (S= 0) at the ground state.[21] Thus, comparison of the reactivity of analogous high-valent metal–oxo species with different spin states has never been made.We report herein for the first time the spin state alteration of RuIV–oxo complexes with tris (2-pyridylmethyl) amine (tpa) derivatives depending on the type of tpa derivatives. Two RuII–aqua complexes having tpa derivatives, tetradentate tpa and a pentadentate N, N-bis (2-pyridylmethyl)-N-(6-carboxylato-2-pyridyl-methyl) amine (6-COOÀ-tpa) monoanion,[Ru-(tpa)(H2O) 2] 2+(1)[13] and [Ru (6-COOÀ-tpa)(H2O)]+(2), were converted into the corresponding RuIV–oxo complexes by the PCET reactions with use of (NH4) 2 [CeIV (NO3) 6](CAN) as an oxidant. Now we have two kinds of RuIV–oxo complexes,[Ru (O)(tpa)(H2O)] 2+(3) in the S= 1 spin state and [Ru (O)(6-COOÀ-tpa)]+(4) in the S= 0 spin state. Thus, analogous RuIV–oxo complexes with different spin states in hand provide an excellent opportunity to compare the reactivity toward substrates in light of their spin states. The RuII–aqua complex 2 was prepared by the reaction of a precursor complex[Ru (6-COOÀ-tpa) Cl] PF6 (see Figure 1)[22] with AgPF6 in water by dechlorination and