Relative energies of α and β isomers of Keggin dodecatungstogallate

Karthik M. Sundaram; Wade A. Neiwert; Craig L. Hill; Ira A. Weinstock

doi:10.1021/ic051789n

Relative energies of α and β isomers of Keggin dodecatungstogallate

Karthik M. Sundaram, Wade A. Neiwert, Craig L. Hill, Ira A. Weinstock

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Abstract

The relative energies of β Keggin heteropolytungstates, X ⁿ⁺W₁₂O₄₀^(8-n)-, decrease as X ⁿ⁺ is varied within period 3, from P⁵⁺ to Si⁴⁺ to Al³⁺. With heating of α-H₅Ga³⁺W ₁₂O₄₀ at 200°C in water, an equilibrated mixture of α (T_d one ¹⁸³W NMR signal) and β (C _3v; three signals; 1:2:1 ratio) isomers is obtained. From ΔG_exp = -RT In K_β→α, in which (from ⁷¹Ga NMR spectra) K_β→α (= [α]/[β]) = 5.0, β-GaW₁₂O₄₀^5- is 0.65 kcal mol^-1 higher in energy than α-GaW₁₂O ₄₀^5-. This finding is evaluated by analysis of the X-ray crystal structure α-K₂Na₃[GaW₁₂O ₄₀]·9.3H₂O [trigonal, space group P3₂21, a = 18.9201(13) Å, b = 18.9201(13) Å, c = 12.5108(12) Å, Z = 3, T = 100(2)K], comparison of the Shannon and Prewitt radii and Pauling electronegativities of Al³⁺ and Ga³⁺, and insight from density functional theory calculations, which predicted Eβ - Eα = 0.32 kcal mol^-1.

Original language	English
Pages (from-to)	958-960
Number of pages	3
Journal	Inorganic Chemistry
Volume	45
Issue number	3
DOIs	https://doi.org/10.1021/ic051789n
State	Published - 6 Feb 2006
Externally published	Yes

ASJC Scopus subject areas

Physical and Theoretical Chemistry
Inorganic Chemistry

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@article{baa62547ac6c4f38a00f7fe83d255ca7,

title = "Relative energies of α and β isomers of Keggin dodecatungstogallate",

abstract = "The relative energies of β Keggin heteropolytungstates, X n+W12O40(8-n)-, decrease as X n+ is varied within period 3, from P5+ to Si4+ to Al3+. With heating of α-H5Ga3+W 12O40 at 200°C in water, an equilibrated mixture of α (Td one 183W NMR signal) and β (C 3v; three signals; 1:2:1 ratio) isomers is obtained. From ΔGexp = -RT In Kβ→α, in which (from 71Ga NMR spectra) Kβ→α (= [α]/[β]) = 5.0, β-GaW12O405- is 0.65 kcal mol-1 higher in energy than α-GaW12O 405-. This finding is evaluated by analysis of the X-ray crystal structure α-K2Na3[GaW12O 40]·9.3H2O [trigonal, space group P3221, a = 18.9201(13) {\AA}, b = 18.9201(13) {\AA}, c = 12.5108(12) {\AA}, Z = 3, T = 100(2)K], comparison of the Shannon and Prewitt radii and Pauling electronegativities of Al3+ and Ga3+, and insight from density functional theory calculations, which predicted Eβ - Eα = 0.32 kcal mol-1.",

author = "Sundaram, {Karthik M.} and Neiwert, {Wade A.} and Hill, {Craig L.} and Weinstock, {Ira A.}",

year = "2006",

month = feb,

day = "6",

doi = "10.1021/ic051789n",

language = "English",

volume = "45",

pages = "958--960",

journal = "Inorganic Chemistry",

issn = "0020-1669",

publisher = "American Chemical Society",

number = "3",

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T1 - Relative energies of α and β isomers of Keggin dodecatungstogallate

AU - Sundaram, Karthik M.

AU - Neiwert, Wade A.

AU - Hill, Craig L.

AU - Weinstock, Ira A.

PY - 2006/2/6

Y1 - 2006/2/6

N2 - The relative energies of β Keggin heteropolytungstates, X n+W12O40(8-n)-, decrease as X n+ is varied within period 3, from P5+ to Si4+ to Al3+. With heating of α-H5Ga3+W 12O40 at 200°C in water, an equilibrated mixture of α (Td one 183W NMR signal) and β (C 3v; three signals; 1:2:1 ratio) isomers is obtained. From ΔGexp = -RT In Kβ→α, in which (from 71Ga NMR spectra) Kβ→α (= [α]/[β]) = 5.0, β-GaW12O405- is 0.65 kcal mol-1 higher in energy than α-GaW12O 405-. This finding is evaluated by analysis of the X-ray crystal structure α-K2Na3[GaW12O 40]·9.3H2O [trigonal, space group P3221, a = 18.9201(13) Å, b = 18.9201(13) Å, c = 12.5108(12) Å, Z = 3, T = 100(2)K], comparison of the Shannon and Prewitt radii and Pauling electronegativities of Al3+ and Ga3+, and insight from density functional theory calculations, which predicted Eβ - Eα = 0.32 kcal mol-1.

AB - The relative energies of β Keggin heteropolytungstates, X n+W12O40(8-n)-, decrease as X n+ is varied within period 3, from P5+ to Si4+ to Al3+. With heating of α-H5Ga3+W 12O40 at 200°C in water, an equilibrated mixture of α (Td one 183W NMR signal) and β (C 3v; three signals; 1:2:1 ratio) isomers is obtained. From ΔGexp = -RT In Kβ→α, in which (from 71Ga NMR spectra) Kβ→α (= [α]/[β]) = 5.0, β-GaW12O405- is 0.65 kcal mol-1 higher in energy than α-GaW12O 405-. This finding is evaluated by analysis of the X-ray crystal structure α-K2Na3[GaW12O 40]·9.3H2O [trigonal, space group P3221, a = 18.9201(13) Å, b = 18.9201(13) Å, c = 12.5108(12) Å, Z = 3, T = 100(2)K], comparison of the Shannon and Prewitt radii and Pauling electronegativities of Al3+ and Ga3+, and insight from density functional theory calculations, which predicted Eβ - Eα = 0.32 kcal mol-1.

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DO - 10.1021/ic051789n

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JO - Inorganic Chemistry

JF - Inorganic Chemistry

IS - 3

ER -

Relative energies of α and β isomers of Keggin dodecatungstogallate

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