Size-Dependent Association of Cobalt Deuteride Cluster Anions Co 3 D n − ( n = 0–4) with Dinitrogen

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