Zirconium-Substituted Isopolytungstates: Structural Models for Zirconia-Supported Tungsten Catalysts

The synthesis and characterization of a series of mixed W−Zr polynuclear Lindqvist-type complexes, deriving from
hexatungstate [W6O19]2-, are described in this work. This family of compounds is built from {W5O18Zr}2- moieties
as shown by the X-ray structures of the monomeric [W5O18Zr(H2O)3-n(DMSO)n]2- (n = 1 and 2) and dimeric
[{W5O18Zr(μ-OH)}2]6- anions. A comprehensive spectroscopic study (183W NMR, FTIR, Raman, EXAFS, and EPR)
of these compounds is presented. The goal of incorporating ZrIV cations into an oxotungstic core is to obtain
spectroscopic models that could mimic the interactions that develop in supported catalysts between the active
phase and the supporting oxide. This work tends to show that these molecular compounds can be regarded as
soluble structural analogues of WOx/ZrO2 catalysts, which are interesting candidates for the skeletal isomerization
of light n-alkanes.