Surface chemistry of Rh carbonyls and nitrosyls on dealuminated Y-zeolite at low temperature

Abstract

FTIR spectroscopy at low temperature (77–300 K) has been used to study the surface species formed during the interaction of CO and NO with Rh^I(CO)₂ and Rh^I(NO)₂ on highly dealuminated zeolite Y (US-Ex). A series of different well defined surface carbonyls and nitrosyls including mixed NO–CO compounds was obtained in addition to the dicarbonyl and dinitrosyl. With CO a Rh tricarbonyl with C_3v symmetry and a tetracarbonyl with C_2v symmetry are suggested and identified by ligand exchange with ¹²C¹⁸O and ¹³C¹⁶O and a calculation of the force constants within the framework of an energy-separated force field. As an intermediate in the ligand exchange reaction between Rh^I(CO)₂ and Rh^I(NO)₂ the mixed surface compound Rh^I(CO)(NO)₂ could be identified.