EXAFS characterization and spectroscopic FT–IR studies of the reactions of the surface species formed upon adsorption or Ir 2(η-Cl) 2(COD) 2 on γ-alumina

Abstract

The adsorption of Ir 2(η-Cl) 2(COD) 2 ( 1) (COD = cyclooctadiene) on alumina has been studied by EXAFS at the LIII edge of Ir. The reactions of the surface complex formed upon adsorption of 1, with CO and PPh 3 have been investigated by FT–IR spectroscopy. The attachment of 1 on γ-alumina involves the replacement of the bridging chloride ligands by aluminato groups of the support, to form a dimeric surface complex formulated as Ir 2(η- O-alumina) 2(COD) 2. The room temperature reaction of this species with CO gives Ir 2(CO) 4(η- O-alumina) 2. This tetracarbonyl surface species reacts at room temperature with PPh 3, to give trans-Ir 2(η- O-alumina) 2 (CO) 2(PPh 3 2. These new surface complexes have considerable potential as precursors for modified iridium-based reforming catalysts.