Synthesis, structure, and reactivity of polyoxovanadates in nonaqueous media

Yaghi, Omar M.

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https://hdl.handle.net/2142/20991 Copy

Description

Title

Synthesis, structure, and reactivity of polyoxovanadates in nonaqueous media

Author(s)

Yaghi, Omar M.

Issue Date

1990

Doctoral Committee Chair(s)

Klemperer, Walter G.

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Chemistry, Inorganic

Language

eng

Abstract

• Exploration of the nonaqueous chemistry of polyoxovanadates was initiated by studying the following reaction: x $\rm H\sb3V\sb{10}O\sb{28}\sp{3-}$ + y OH$\sp-$ $\to$ 10 $\rm H\sb nV\sb xO\sb m\sp{z-}$ + (y-n) H$\sb2$O involving the addition of (TBA)(OH) to ($\rm H\sb3V\sb{10}O\sb{28}$)(TBA)$\sb3$ in CH$\sb3$CN, where TBA = tetra-n-butylammonium. This resulted in the synthesis and characterization of two types of soluble species: first, reactive isopolyvanadate species which can serve as good starting materials for the development of the synthetic chemistry of covalent polyoxovanadate derivatives; second, species which have structural features normally associated with those present on solid vanadium oxide surfaces. The first species isolated from this reaction was $\rm H\sb2V\sb{10}O\sb{28}\sp{4-}$ as a TBA salt, structural characterization in the solid and solution state reveal that the protonation sites are two OV$\sb2$ oxygens. This anion was found to be unstable in acetonitrile with respect to disproportionation forming two new polyoxovanadates, $\rm V\sb5O\sb{14}\sp{3-}$ and $\rm V\sb{12}O\sb{32}\sp{4-}$.
• The $\rm V\sb{12}O\sb{32}\sp{4-}$ anion is formed as an acetonitrile inclusion complex, $\rm CH\sb3CN\subset(V\sb{12}O\sb{32}\sp{4-}$). The nido-$\rm V\sb{12}O\sb{32}\sp{4-}$ cage framework is a new structure type and can be derived from two different types of closo-cage frameworks. The vanadium coordination geometry within the $\rm V\sb{12}O\sb{32}\sp{4-}$ cage is similar to that observed in square-pyramidal vanadium(V) compounds such as orthorhombic $\rm V\sb2O\sb5$ and $\alpha$-VOPO$\sb4$.
• The $\rm V\sb{12}O\sb{32}\sp{4-}$ is the first molecular inorganic species known to form inclusion complexes in solution. Synthesis and structural characterization of the $\rm CH\sb3NO\sb2$, $\rm C\sb6H\sb5NO\sb2$, p-$\rm CH\sb3C\sb6H\sb4CN$, $\rm C\sb6H\sb5CN$, $\rm NCCH\sb2CH\sb2CN$ and 1,2-$\rm CH\sb2CH\sb2Cl\sb2$ host-guest complexes has been achieved. The equilibrium constants for host-guest complexation have been derived, and in some cases the enthalpy and entropy of binding have been established quantitatively.
• The structural analogy between orthorhombic $\rm V\sb2O\sb5$ layers and $\rm V\sb{12}O\sb{32}\sp{4-}$ host molecules, raises the possibility that this host framework might be capable of affecting C-H activation. Coordinatively unsaturated vanadium sites in vanadates such as $\rm (VO)\sb2P\sb2O\sb7$ can react with $\rm CH\sb3CN$ molecules. The remaining question is whether $\rm V\sb{12}O\sb{32}\sp{4-}$ can react with saturated hydrocarbons. (Abstract shortened with permission of author.)

Type of Resource

text

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http://hdl.handle.net/2142/20991

Copyright and License Information

Copyright 1990 Yaghi, Omar M.

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