Structure and bonding of a site-isolated transition metal complex: Rhodium dicarbonyl in highly dealuminated zeolite y

The structure and bonding of rhodium dicarbonyl bonded to highly dealuminated zeolite Y has been determined by the combined application of extended X-ray absorption fine structure (EXAFS) and infrared spectroscopies and quantum chemical calculations based on density functional theory. The EXAFS and infrared spectra indicate the existence of nearly unique rhodium dicarbonyl species bonded at structurally equivalent positions in the zeolite pores. However, even this anchored structure, one of the simplest known, is not determined fully by the experimental results, and quantum chemical calculations were needed to eliminate the ambiguity. Taken together, the experimental and theoretical results indicate Rh⁺(CO)₂ located at a four-ring of the faujasite framework; the rhodium center is bonded to two oxygen centers of the framework near an aluminum center with a Rh - O distance of 2.15-2.20 Å. The results show how spectroscopy and theory used in combination can determine the structure and location of a metal complex anchored to a structurally uniform support.