Surface Photochemistry of Rh(CO)2 on Zeolite YProduction of a Stable Coordinatively Unsaturated Rhodium Monocarbonyl Surface Species at Room Temperature

The photochemical production and chemical reactivity of a new coordinatively unsaturated rhodium monocarbonyl species on the surface of dealuminated zeolite Y over a temperature range of 300−420 K and a pressure range from 10-5 to 20 Torr has been studied. Using high vacuum techniques and transmission infrared spectroscopy, ultraviolet irradiation (350 ± 50 nm) of supported Rh(CO)2 surface species led to the production of stable, but reactive, Rh(CO) surface species, characterized by an infrared band at 2023 cm-1. The coordinatively unsaturated Rh(CO) species convert to less reactive and coordinatively saturated ⋮Rh(CO) by thermal treatment above 370 K. The ⋮Rh(CO) species were characterized by an infrared band at 2013 cm-1. An explanation of the mode of bonding of the rhodium monocarbonyl species to the zeolite surface is provided. Coordinatively unsaturated Rh(CO) species captured N2, H2, and O2 gas molecules near room temperature to produce a variety of mixed ligand rhodium surface complexes of the form Rh(CO)(N2), Rh(CO)(H2), Rh(CO)(H)2, Rh(CO)(H), Rh(CO)(O), and Rh(O). Infrared band assignments for the new species are provided. The work provides new insight into the photochemical behavior of Rh(CO)2 species supported on high-area zeolite materials and may improve our understanding of the role of active rhodium monocarbonyl species in the development of heterogeneous photocatalysts.