Size-Dependent Association of Cobalt Deuteride Cluster Anions CoD (n = 0-4) with Dinitrogen.

Dinitrogen (N) activation by metal hydride species is of fundamental interest and practical importance while the role of hydrogen in N activation is not well studied. Herein, the structures of CoD (n = 0-4) clusters and their reactions with N have been studied by using a combined experimental and computational approach. The mass spectrometry experiments identified that the CoD (n = 2-4) clusters could adsorb N while the CoD (n = 0 and 1) clusters were inert. The photoelectron imaging spectroscopy indicated that the electron detachment energies of CoD are smaller than those of CoD, which characterized that it is easier to transfer electrons from CoD than from CoD to activate N. The density functional theory calculations generally supported the experimental observations. Further analysis revealed that the H atoms in the CoH (n = 2-4) clusters generally result in higher energies of the Co 3d orbitals in comparison with the CoH (n = 0 and 1) systems. By forming chemical bonds with H atoms, the Co atoms of CoH are less negatively charged with respect to the naked Co system, which leads to higher N binding energies of CoHN than that of CoN.