Nitrogen Chemisorption on the Coordinatively Unsaturated Rh Site on Al₂O₃

Abstract

The UV (3.8 eV) photolysis of atomically-dispersed Rh I (CO) 2 species supported on an Al 2 O 3 surface in the presence of N 2 at 175 K caused the replacement of CO by N 2 ligands. Therefore dinitrogen chemisorption effectively probes the coordinatively unsaturated Rh(CO) species generated during photodecomposition of Rh I (CO) 2 / Al 2 O 3 . Two infrared bands, observed at 2234 and 2048 cm -1 , are attributed respectively to ν N2 and ν CO in Rh(N 2 )(CO), and a band at 2188 cm -1 is assigned to Rh(N 2 ) 2 surface species. The assignments are based on frequencies and the relative rates of spectral development for the two N 2 -containing species. The Rh(N 2 ) 2 species on Al 2 O 3 exhibits identical N-N stretching modes to a similar species produced by matrix isolation methods. It is shown that both the Rh-CO bond and the Rh-N 2 bond may be broken by photolysis.

Identification of Neutral and Charged NxOySurface Species by IR Spectroscopy

“…Most of the cases concern Cu ϩ cations in zeolites, where a band assigned to adsorbed dinitrogen has been detected in the 2299-2290-cm Ϫ1 region [32,[129][130][131]. A strong adsorption of N 2 has been reported for Rh ϩ -exchanged zeolites [132] and Rh/Al 2 O 3 [133], where formation of geminal species has been observed. The band has been detected after adsorption of dinitrogen [130,131] or under reaction conditions [32,129].…”

Mononuclear Iridium Dinitrogen Complexes Bonded to Zeolite HY

“…Among the best-defined molecular metal complexes in this class are dinitrogen species consisting of one or a few transition metal atoms and exhibiting various N 2 binding geometries. [1f, i] N 2 reacts with metal atoms at about 10 K in a matrix to form metal-nitrogen complexes of the family M(N 2 ) n , where n = 1-3 or 4 or 5,and M includes Rh,Ni,Pd,Pt,Co,and Fe. In these cases, the metal complexes work with metals that are strong reducing agents (for example, KC 8 [1a-c, h] or Na/Hg [1g] ) or incorporate highly reactive hydride ligands.…”

“…[1f, i] N 2 reacts with metal atoms at about 10 K in a matrix to form metal-nitrogen complexes of the family M(N 2 ) n , where n = 1-3 or 4 or 5,and M includes Rh,Ni,Pd,Pt,Co,and Fe. [5] Species incorporating only one or a few metal atoms usually bond to nitrogen more strongly than extended metal surfaces. [4] N 2 is only weakly chemisorbed on metals, and the infrared (IR) spectra characterizing nitrogen on supported metals (for example, Pt/ SiO 2 , Rh/Al 2 O 3 , Ru/Al 2 O 3 , and Ir/SiO 2 ) have been observed only at low temperatures or high pressures.…”

Possible catalytic effects of ice particles on the production of NO<sub>x</sub> by lightning discharges

“…Chemisorption occurring through nitrogen-hydrogen chemical bonding is the most likely adsorption mechanism. Certainly there is a precedent for consideration of these types of chemisorptive catalytic reactions, as it has been found Franzblau and Popp (1989) Field study 3.00 × 10 27 4981.73 that the rate of catalytic ammonia synthesis is primarily determined by nitrogen chemisorption (Klimisch and Larson, 1975); many other reactions are also dictated by nitrogen chemisorption (Shinn, 1990;Wovchko and Yates, 1996;Ertl et al, 1979). The greatest amount of adsorption per unit of ice particles probably occurs with the dendrite crystal habit, since dendrites have the largest specific surface area (Fig.…”