Cryokinetics and spin quenching in the N₂ adsorption onto rhodium cluster cations

Abstract

The kinetics of N 2 adsorption onto gas phase Rh i + clusters (i = 5-15) within 26 K He buffer gas have been investigated by Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometry, with particular focus to clusters i = 5,6,7,9. The adsorption limits m = m max of [Rh i (N 2 ) m ] + clusters strongly depend on the size of the clusters. Some Rh i + clusters reveal an intermittent adsorption limit m x , which implies a rough cluster surface. Most of the clusters reveal smooth surfaces, which consist of Rh atoms with similar next neighbour coordination. The kinetic fits and relative rate constants reveal the sequential adsorption of N 2 as the only significant reaction channel. In some cases, we find N 2 desorption steps at high N 2 loads indicating adsorption-desorption equilibria. For these steps, we determined Gibbs energies from the relative rate constants. We observed a significant reluctance towards N 2 adsorption for the Rh 5 + cluster, indicated by significant desorption at low N 2 coverage. Our DFT calculations model the energetics of the N 2 adsorption onto Rh 5 + in terms of coverage dependent 'spin valley' curves, and we conclude that an adsorption induced spin quenching takes place upon considerable N 2 coverage, m > 4.

Ladder Oxygenation of Group VIII Metal Clusters and the Formation of Metalloxocubes M13O8+

“…Mafuné and co-workers measured the threshold energies for O 2 desorption from Rh n O m + clusters . Asmis, He, and co-workers studied the catalytic conversion of CH 4 and CO 2 to produce syngas and found that the rhodium oxide clusters participated in the catalytic reactions as important intermediates or transition states. , …”