The N2O activation by Rh5 clusters. A quantum chemistry study

Nitrous oxide (N 2 O) is a by-product of exhaust pipe gases treatment produced by motor vehicles. Therefore, the N 2 O reduction to N 2 is necessary to meet the actual environmental legislation. The N 2 O adsorption and dissociation assisted by the square-based pyramidal Rh 5 cluster was investigated using the density functional theory and the zero-order regular approximation (ZORA). The Rh 5 sextet ground state is the most active in N 2 O dissociation, though the quartet and octet states are also active because they are degenerate. The Rh 5 cluster spontaneously activates the N 2 ─O cleavage, and the reaction is highly exothermic ca. -75 kcal mol -1 . The N 2 ─O breaking is obtained for the geometrical arrangement that maximizes the overlap and electron transfers between the N 2 O and Rh 5 frontier orbitals. The Rh 5 high activity is due to the Rh 3d orbitals are located between the N 2 O HOMO and LUMO orbitals, which makes possible the interactions between them. In particular, the O 2p states strongly interact with Rh 3d orbitals, which finally weaken the N 2 ─O bond. The electron transfer is from the Rh 5 HOMO orbital to the N 2 O antibonding orbital. Graphical Abstract N 2 O activation by Rh 5 clustersᅟ