Laser-ablated tantalum and niobium atoms react with CO and N(2) mixtures in excess neon to produce carbonyl metal dinitrogen complexes, NNMCO (M = Ta, Nb), (NN)(2)TaCO, and NNTa(CO)(2), as well as metal carbonyls and dinitrogen complexes. These carbonylmetal dinitrogen complexes are characterized using infrared spectroscopy on the basis of the results of the isotopic substitution and mixed isotopic splitting patterns. Density functional theory calculations have been performed on these novel species. The good 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. Natural bond orbital analysis and plausible reaction mechanisms for the formation of the products are discussed.