Dimeric assemblies of lanthanide-stabilised dilacunary Keggin tungstogermanates: A new class of catalysts for the selective oxidation of aniline

• Na12[Ln4(H2O)6(GeW10O38)2] salts (Ln = Dy to Tm) catalyse the oxidation of aniline.
• They are excellent heterogeneous catalysts fully selective towards nitrosobenzene.
• Superficial peroxometallic species are the real active sites for the reaction.
• Thermal pre-treatment of the catalysts leads to higher catalytic activities.
• The process is eco-friendly, clean, and cheap.

In this work we demonstrate the efficiency of some dimeric [Ln4(H2O)6(β-GeW10O38)2]12− anions composed of lanthanide-stabilised dilacunary Keggin tungstogermanate fragments (ββ-Ln4, Ln = Dy, Ho, Er, Tm) as heterogeneous catalysts for the organic phase oxidation of aniline with hydrogen peroxide. The results obtained evidence total conversion of aniline at room temperature, as well as full selectivity towards nitrosobenzene, and the catalysts are able to retain both their activity and selectivity after several runs. Peroxopolyoxometalate intermediaries have been identified as the catalytically active species during the aniline-to-nitrosobenzene oxidation process.

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