Mbomekalle Israel Martyr, Keita Bineta, Nadjo Louis, Berthet Patrick, Hardcastle Kenneth I, Hill Craig L, Anderson Travis M
Laboratoire de Chimie Physique, UMR 8000, CNRS, Université Paris-Sud, Bâtiment 420, 91405 Orsay Cedex, France.
Inorg Chem. 2003 Feb 24;42(4):1163-9. doi: 10.1021/ic0261169.
Reaction of the trivacant lacunary complex, alpha-Na(12)[As(2)W(15)O(56)], with an aqueous solution of Fe(NO(3))(3).9H(2)O yields the sandwich-type polyoxometalate, alphabetabetaalpha-Na(12)(Fe(III)OH(2))(2)Fe(III)(2)(As(2)W(15)O(56))(2) (Na1). The structure of this complex, determined by single-crystal X-ray crystallography (a = 13.434(1) A, b = 13.763(1) A, c = 22.999(2) A, alpha = 90.246(2) degrees, beta = 102.887(2) degrees, gamma = 116.972(1) degrees, triclinic, Ponemacr;, R1 = 5.5%, based on 25342 independent reflections), consists of an Fe(III)(4) unit sandwiched between two trivacant alpha-As(2)W(15)O(56)(12)(-) moieties. UV-vis, infrared, cyclic voltammetry, and elemental analysis data are all consistent with the structure determined from X-ray analysis. Magnetization studies confirm that the four Fe(III) centers are antiferromagnetically coupled. A cyclic voltammogram of Na1 reveals that a three-wave W(VI) system replaces the two-wave W(VI) system found in the precursor alpha-As(2)W(15)O(56)(12)(-) complex. The observed modifications in the CV patterns of Na1 and alpha-As(2)W(15)O(56)(12)(-) are most likely due to subsequent changes in the acid-base properties of two reduced POMs that occur as a result of Fe(III) incorporation. Na1 is shown to be more efficient than the monosubstituted complex alpha(2)-As(2)(Fe(III)OH(2))W(17)O(61)(7)(-) in the electrocatalytic reduction of dioxygen. This is attributed to cooperativity effects among the adjacent Fe(III) centers in Na1.
三缺位空穴配合物α-Na(12)[As(2)W(15)O(56)]与Fe(NO(3))(3).9H(2)O的水溶液反应，生成夹心型多金属氧酸盐αββα-Na(12)(Fe(III)OH(2))(2)Fe(III)(2)(As(2)W(15)O(56))(2)（Na1）。通过单晶X射线晶体学确定该配合物的结构（a = 13.434(1) Å，b = 13.763(1) Å，c = 22.999(2) Å，α = 90.246(2)°，β = 102.887(2)°，γ = 116.972(1)°，三斜晶系，P1，基于25342个独立反射，R1 = 5.5%），其结构由夹在两个三缺位α-As(2)W(15)O(56)(12)(-)部分之间的一个Fe(III)(4)单元组成。紫外可见光谱、红外光谱、循环伏安法和元素分析数据均与X射线分析确定的结构一致。磁化研究证实四个Fe(III)中心是反铁磁耦合的。Na1的循环伏安图显示，一个三波W(VI)体系取代了在前体α-As(2)W(15)O(56)(12)(-)配合物中发现的两波W(VI)体系。在Na1和α-As(2)W(15)O(56)(12)(-)的循环伏安图中观察到的变化很可能是由于由于Fe(III)掺入导致的两种还原多金属氧酸盐的酸碱性质的后续变化。结果表明，在电催化还原氧气方面，Na1比单取代配合物α(2)-As(2)(Fe(III)OH(2))W(17)O(61)(7)(-)更有效。这归因于Na1中相邻Fe(III)中心之间的协同效应。
