Uranium was laser-ablated in the presence of N-2/Ar mixtures, and the reaction products were studied using matrix isolation infrared spectroscopy. These reactions were studied over a wide range of N-2 concentrations in Ar (0.1% to 50%) and also with pure N-2. We observed that at low N-2 concentrations in Ar (<1%), the reaction product was the insertion product UN2 and its complexes with molecular N-2, a result that agreed xwith an earlier report of Andrews and group. Interestingly, however, as the N-2 concentration was increased, we observed the formation of the mononitride, UN. We believe that as the N-2 concentration is increased, new reaction channels open up, resulting in the formation of nitrogen atoms and N-3 species which then react with laser-ablated uranium atoms to produce UN. The assignment of the infrared feature due to UN in a N-2 matrix is also discussed.