Characterization of NaY zeolite-encaged tetrairidium clusters by infrared and x-ray absorption spectroscopies

Abstract

[Ir(CO)[sub 2](acac)] in the pores of NaY zeolite was treated in CO and converted into [Ir[sub 4](CO)[sub 12]]. The zeolite-encaged [Ir[sub 4](CO)[sub 12]] was characterized by infrared and extended X-ray absorption fine structure spectroscopies, with the data indicating an average Ir-Ir coordination number of 2.6 and an average Ir-Ir distance of 2.69 [angstrom], in agreement, within the experimental error, with the published crystallographic data for solid [Ir[sub 4](CO)[sub 12]]. Structurally simple zeolite-encaged iridium clusters were made by decarbonylation of the [Ir[sub 4](CO)[sub 12]] at 325[degree]C in flowing He followed by H[sub 2]. The decarbonylated clusters had an average Ir-Ir coordination number of 3.4 and a bond distance of 2.70 [angstrom], consistent with the inference that the tetrahedral framework structure of [Ir[sub 4](CO)[sub 12]] had been retained after decarbonylation; thus, the cluster is represented as tetrahedral Ir[sub 4]. Infrared spectra showed that [Ir[sub 4](CO)[sub 12]] was re-formed when the sample was treated in CO at 60[degree]C. 63 refs., 6 figs., 3 tabs.