Formation, Isomerization, and Derivatization of Keggin Tungstoaluminates
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- 作者：Jennifer J. Cowan ; Alan J. Bailey ; Robert A. Heintz ; Bao T. Do ; Kenneth I. Hardcastle ; Craig L. Hill ; and Ira A. Weinstock
- 刊名：Inorganic Chemistry
- 出版年：2001
- 出版时间：December 17, 2001
- 年：2001
- 卷：40
- 期：26
- 页码：6666 - 6675
- 全文大小：171K
- 年卷期：v.40,no.26(December 17, 2001)
- ISSN：1520-510X
文摘
Trends in the stability of 
- and 
-Keggin heteropolytungstates of the second-row main-group heteroatoms Al(III), Si(IV), and P(V) are elaborated by data that establish the roles of kinetic and thermodynamic control in theformation and isomerization of Keggin tungstoaluminates. Slow, room-temperature co-condensation of Al(III)and W(VI) (2:11 molar ratio) in water gives a pH 7 solution containing 1 and 2 isomers of [Al(AlOH2)W11O39]6-(1- and 2-1). Partial equilibration of this kinetic product mixture by gentle heating (2 h at 100 
C) or, alternatively,co-condensation of Al(III) and W(VI) for 2.5 h at 100 C both give mixtures of 2-, 3-, and -1. Full equilibration,by prolonged heating (25 days at 100 C), gives an isomerically pure solution of -1, thus demonstrating thatisomerization occurs in the direction 1 
2 3 . Furthermore, kinetically controlled conversions of 1 toH5[AlW12O40] (2)-achieved by heating pH 0-0.2 solutions of 1 for 5 days at 100 C-occur with retention ofisomeric integrity, such that -1 is converted to -2 (92%; 8% ), while mixtures of 2- and 3-1 are convertedto -2 (87%; 13% ). These data, when combined with previously reported observations (equilibria between -and -2, kinetically controlled hydrolyses of -2 to -[AlW11O39]9- (-3) and of -2 to 2-3, and equilibriabetween 3- and -3), provide a comprehensive picture regarding the roles of kinetic and thermodynamic control.Finally, a general method for preparation of the isomerically pure derivatives -K9-n[AlMn+W11O39] (4), Mn+ =Al(III), [VIVO]2+, [VVO]3+, Mn(II), Mn(III), Mn(IV), Co(II), and Co(III), is provided. The presence of Mn(IV)is confirmed by cyclic voltammetry, pKa values of the aquo ligands on 4 are determined by pH titration, and theisomeric structure of these derivatives is established by 27Al, 51V, and 183W NMR and IR spectroscopies andX-ray crystallography.
- and -Keggin heteropolytungstates of the second-row main-group heteroatoms Al(III), Si(IV), and P(V) are elaborated by data that establish the roles of kinetic and thermodynamic control in theformation and isomerization of Keggin tungstoaluminates. Slow, room-temperature co-condensation of Al(III)and W(VI) (2:11 molar ratio) in water gives a pH 7 solution containing 1 and 2 isomers of [Al(AlOH2)W11O39]6-(1- and 2-1). Partial equilibration of this kinetic product mixture by gentle heating (2 h at 100 C) or, alternatively,co-condensation of Al(III) and W(VI) for 2.5 h at 100 C both give mixtures of 2-, 3-, and -1. Full equilibration,by prolonged heating (25 days at 100 C), gives an isomerically pure solution of -1, thus demonstrating thatisomerization occurs in the direction 1 2 3 . Furthermore, kinetically controlled conversions of 1 toH5[AlW12O40] (2)-achieved by heating pH 0-0.2 solutions of 1 for 5 days at 100 C-occur with retention ofisomeric integrity, such that -1 is converted to -2 (92%; 8% ), while mixtures of 2- and 3-1 are convertedto -2 (87%; 13% ). These data, when combined with previously reported observations (equilibria between -and -2, kinetically controlled hydrolyses of -2 to -[AlW11O39]9- (-3) and of -2 to 2-3, and equilibriabetween 3- and -3), provide a comprehensive picture regarding the roles of kinetic and thermodynamic control.Finally, a general method for preparation of the isomerically pure derivatives -K9-n[AlMn+W11O39] (4), Mn+ =Al(III), [VIVO]2+, [VVO]3+, Mn(II), Mn(III), Mn(IV), Co(II), and Co(III), is provided. The presence of Mn(IV)is confirmed by cyclic voltammetry, pKa values of the aquo ligands on 4 are determined by pH titration, and theisomeric structure of these derivatives is established by 27Al, 51V, and 183W NMR and IR spectroscopies andX-ray crystallography.