Surface Organometallic Chemistry on Metals. Catalytic Hydrogenation of Nitrobenzene into Aniline on Silica Supported Rhodium Modified by Tetrabutyltin.

A bimetallic rhodium-tin on silica catalyst has been prepared through the decomposition of alkyltin over supported rhodium in operating conditions resulting in a surface species still containing two alkyl radicals per tin atom. Characterization by CO chemisorption, IR and XPS demonstrates that this phase is a mixture of Sn⁽⁰⁾and Sn⁽ⁿ⁺⁾where rhodium atoms remain still accessible and adjacent even with the addition of one tin atome per rhodium. This surface is active and selective for the hydrogenation of nitrobenzene into aniline, insharp contrast with pure rhodium or rhodium-tin surfaces whitout alkyls. A model of a tin “double layer” stabilized by the presence of alkyls rationalizes this unusual behaviour.