Reactions of laser-ablated Y and La atoms with N2O molecules in excess argon have been investigated using matrix-isolation infrared spectroscopy. Metal monoxide - dinitrogen complexes, OM(N-2) (M = Y, La) and OYNN, have been formed during sample deposition and identified on the basis of isotopic shifts, mixed isotopic splitting patterns, and CCl4-doping experiments. The OYNN+ and OLaNN+ cation complexes appear during sample deposition and increase visibly upon broad-band irradiation (lambda > 250 nm) at the expense of the neutral metal monoxide-dinitrogen complexes. Density functional theory calculations have been performed on the products. The agreement between the experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts supports the identification of these species from the matrix infrared spectra. Furthermore, a plausible reaction mechanism for the formation of these products has been proposed.