The role of the heteroatom (X聽=聽SiIV, PV, and SVI) on the reactivity of {纬-[(H2O)RuIII(渭-OH)2RuIII(H2O)][Xn+W10O36]
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- 作者：Aleksey E. Kuznetsov (12)
Yurii V. Geletii (1)
Craig L. Hill (1)
Keiji Morokuma (1)
Djamaladdin G. Musaev (1) dmusaev@emory.edu - 关键词：Density functional – ; Catalysis – ; Polyoxometalate – ; Water oxidation
- 刊名：Theoretical Chemistry Accounts ; Theory ; Computation ; and Modeling (Theoretica Chimica Acta)
- 出版时间：October 2011
- 出版年：2011
- 期刊代码：108_1432-881X
- 类别：ph
- 卷：130
- 期：2-3
- 页码：197-207
- 数据来源：sp
摘要
The mechanism of reaction of the di-Ru-substituted polyoxometalate, {γ-[(H2O)RuIII(μ-OH)2RuIII(H2O)][X n+W10O36]}(8−n)−, I_X, with O2, i.e. I_X + O2 → {γ-[(路O)RuIV(μ-OH)2RuIV(O路)][X n+W10O36]}(8−n)− + 2H2O, (1), was studied at the B3LYP density functional and self-consistent reaction field IEF-PCM (in aqueous solution) levels of theory. The effect of the nature of heteroatom X (where X = Si, P and, S) on the calculated energies and mechanism of the reaction (1) was elucidated. It was shown that the nature of X only slightly affects the reactivity of I_X with O2, which is a 4-electron oxidation process. The overall reaction (1): (a) proceeds with moderate energy barriers for all studied X’s [the calculated rate-determining barriers are X = Si (18.7 kcal/mol) < S (20.6 kcal/mol) < P (27.2 kcal/mol) in water, and X = S (18.7 kcal/mol) < P (21.4 kcal/mol) < Si (23.1 kcal/mol) in the gas phase] and (b) is exothermic [by X = Si [28.7 (22.1) kcal/mol] > P [21.4 (9.8) kcal/mol] > S [12.3 (5.0) kcal/mol]. The resulting { g- [ ( · \textO ) \textRu\textIV ( m- \textOH )2 \textRu\textIV ( \textO · ) ][ \textX\textn + \textW10 \textO36 ] }( 8 - \textn ) - \left\{ {\gamma - \left[ {\left( {^{ \cdot } {\text{O}}} \right) {\text{Ru}}^{\text{IV}} \left( {\mu - {\text{OH}}} \right)_{2} {\text{Ru}}^{\text{IV}} \left( {{\text{O}}^{ \cdot } } \right)} \right]\left[ {{\text{X}}^{{{\text{n}} + }} {\text{W}}_{10} {\text{O}}_{36} } \right]} \right\}^{{\left( {8 - {\text{n}}} \right) - }} , VI_X, complex was found to have two RuIV = O路 units, rather than RuV = O units. The “reverse” reaction, i.e., water oxidation by VI_X is an endothermic process and unlikely to occur for X = Si and P, while it could occur for X = S under specific conditions. The lack of reactivity of VI_X biradical toward the water molecule leads to the formation of the stable [{Ru4IVO4(OH)2(H2O)4}[(γ-XW10O36]2}m− dimer. This conclusion is consistent with our experimental findings; previously we prepared the [ { \textRu4\textIV \textO4 (\textOH)2 ( \textH 2 \textO )4 } [( g- \textXW10 \textO36 ]2 }\textm - \left[ {\left\{ {{\text{Ru}}_{4}^{\text{IV}} {\text{O}}_{4} ({\text{OH}})_{2} \left( {{\text{H}}_{ 2} {\text{O}}} \right)_{4} } \right\}} \right[\left( {\gamma - {\text{XW}}_{10} {\text{O}}_{36} } \right]_{2} \}^{{{\text{m}} - }} dimers for X = Si (m = 10) [Geletii et al. in Angew Chem Int Ed 47:3896–3899, 2008 and J Am Chem Soc 131:17360–17370, 2009] and P (m = 8) [Besson et al. in Chem Comm 46:2784–2786, 2010] and showed them to be very stable and efficient catalysts for the oxidation of water to O2.