Hydrogen addition reactions with cluster size-dependent

In terms of chemical shift there is clearly a distinction between the hydrogen bonded complex and the silyl ether addition complex, independent of cluster size. The stability of the latter is however strongly dependent on relaxation and has yet to be observed experimentally. It may however exist as a short lived intermediate in catalytic reactions that can not be observed in the time scale of the NMR. The hydrogen bonded complex has in fact been observed experimentally in the case of acetone and the measured shielding tensor is qualitatively found to be in agreement with the results for the ZOH(F) cluster, again indicating the importance of relaxation. 

In the UHV the successful results of the TPR experiments towards ethene hydrogenation on different cluster sizes are further investigated. Vibrational information (IRRAS) in combination with the electronic stfucture (EES) of cluster adsorbates is believed to elucidate the size dependent behavior. In this respect, first isotope experiments with deuterium look promising to elucidate the role of the hydrogen activation in the hydrogenation reaction. In addition, the application of isothermal pMBRS will help to gain kinetic data which will make the results more widely applicable [1 ]. 

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