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Reversible Cation/Anion Extraction from $K_2La_2Ti_3O_{10}$: Formation of New Layered Titanates, $KLa_2Ti_3O_{9.5}$ and $La_2Ti_3O_9$

Gonen, Serpil Z and Paluchowski, Daniel and Zavalij, Peter and Eichhorn, Bryan W and Gopalakrishnan, J (2006) Reversible Cation/Anion Extraction from $K_2La_2Ti_3O_{10}$: Formation of New Layered Titanates, $KLa_2Ti_3O_{9.5}$ and $La_2Ti_3O_9$. In: Inorganic Chemistry, 45 (21). pp. 8736-8742.

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Abstract

A new soft-chemical transformation of layered perovskite oxides is described wherein $K_2O$ is sequentially extracted from the Ruddlesden-Popper (R-P) phase, $K_2La_2Ti_3O_{10}$(I), yielding novel anion-deficient $KLa_2Ti_3O_{9.5}$ (II) and $La_2Ti_3O_9$ (III). The transformation occurs in topochemical reactions of the R-P phase I with $PPh_4Br$ and $PBu_4Br$ (Ph= phenyl; Bu = n-butyl). The mechanism involves the elimination of KBr accompanied by decomposition of $PR_4^+$ (R= phenyl or n-butyl) that extracts oxygen from the titanate. Analysis of the organic products of decomposition reveals formation of $Ph_3PO$, $Ph_3P$, and Ph-Ph for R = phenyl, and $Bu_3PO$, $Bu_3P$ along with butane, butene, and octane for R =butyl. The inorganic oxides II and III crystallize in tetragonal structures (II: P4/mmm, a= 3.8335(1)\AA, c= 14.334(1)\AA; III: I4/mmm, a= 3.8565(2)\AA, c= 24.645(2)\AA) that are related to the parent R-P phase. II is isotypic with the Dion-Jacobson phase, $RbSr_2Nb_3O_{10}$, while III is a unique layered oxide consisting of chargeneutral $La_2Ti_3O_9$ anion-deficient perovskite sheets stacked one over the other without interlayer cations. Interestingly, both II and III convert back to the parent R-P phase in a reaction with $KNO_3$. While transformations of the R-P phases to other related layered/three-dimensional perovskite oxides in ion-xchange/metathesis/dehydration/reduction reactions are known, the simultaneous and reversible extraction of both cations and anions in the conversions $K_2La_2Ti_3O_{10}$\rightleftharpoons $KLa_2Ti_3O_{9.5}$\rightleftharpoons $La_2Ti_3O_9$ is reported here for the first time.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to American Chemical Society
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited: 12 Dec 2006
Last Modified: 19 Sep 2010 04:32
URI: http://eprints.iisc.ernet.in/id/eprint/8934

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