Platinum-proton coupling in the NMR spectrum of benzene on an alumina-supported platinum catalyst

Abstract

The homonuclear decoupled proton NMR spectrum of benzene associatively chemisorbed on a 5.0% wt/wt Pt/A1203 catalyst is reported. The structure of the resonance is attributable to heteronuclear dipolar or pseudodipolar couplings to platinum-195 nuclei in the surface of the particle. Comparison of simulated spectra for benzene molecules in various sites coupled by the heteronuclear dipolar interaction to an array of platinum atoms indicates that only benzene in the "on top" geometry is consistent with the observed spectrum. If the coupling is attributed solely to direct dipolar couplings, the predicted Pt-benzene distance is 1.56 f 0.02 A. Considering both dipolar and pseudodipolar couplings leads to the conclusion that this value is a minimum for the Pt-benzene distance.

Structure and energetics of benzene adsorbed on transition-metal surfaces: density-functional theory with van der Waals interactions including collective substrate response

“…In contrast, Tirendi et al [120] used nuclear magnetic resonance and suggested that Bz molecules are located at the atop site. Inferred from the orientations of the STM images, Weiss and Eigler [121] reported the coexistence of Bz molecules at both the hcp and fcc sites.…”

Linear and Nonlinear Spectroscopy with the Tunable AC Scanning Tunneling Microscope

“…Adsorbed PF 3 on a number of qt metal surfaces is known from ESDIAD measurements to have a bound (hindered) to free rotor transition as the temperature is increased [30][31][32]. Jn NMR experiments, benzene has been shown to rotate on Ft particles which are predominantly textured Pt4 111) [33,34]. STM images of azulene have been interpreted as rapidly rotating molecules [35].…”

Methionine bound to Pd/γ-Al2O3 catalysts studied by solid-state 13C NMR

“…in CO on transition metals. [26][27][28] On the other hand, several studies [29][30][31][32][33][34] have shown that for carbon not directly bonded to the metal, e.g. separated by a heteroatom such as S 30 or physisorbed, [32][33][34] the change in peak position is more moderate, < 20 ppm, and can be used to monitor adsorption.…”

“…[26][27][28] On the other hand, several studies [29][30][31][32][33][34] have shown that for carbon not directly bonded to the metal, e.g. separated by a heteroatom such as S 30 or physisorbed, [32][33][34] the change in peak position is more moderate, < 20 ppm, and can be used to monitor adsorption. [29][30][31][32][33][34] One recent study demonstrated that the chemical shift of formate on different metal nanoparticles correlated well with the calculated dband center, formate decomposition rate, metal work function, and specific activity.…”

“…separated by a heteroatom such as S 30 or physisorbed, [32][33][34] the change in peak position is more moderate, < 20 ppm, and can be used to monitor adsorption. [29][30][31][32][33][34] One recent study demonstrated that the chemical shift of formate on different metal nanoparticles correlated well with the calculated dband center, formate decomposition rate, metal work function, and specific activity. 31 In metaloxide catalysts, 13 C NMR of acetone has been shown to be a viable means for measuring solidacid strength.…”