Infrared spectra and electronic structure calculations for the NUN(NN)1-5 and NU(NN)1-6 complexes in solid argon.

Reactions of laser-ablated U atoms with N2 molecules in excess argon during co-deposition at 4 K gave intense NUN and weaker UN absorptions. Annealing increased progressions of new absorptions for the NUN(NN)1,2,3,4,5 and NU(NN)1,2,3,4,5,6 uranium nitride complexes. Small matrix shifts are observed when the secondary coordination layers around the primary NUN(NN)1,2,3,4,5 and NU(NN)1,2,3,4,5,6 complexes are changed from argon to nitrogen. Electronic structure and energy and frequency calculations provide support for the identification of these complexes and further characterization of the N≡U≡N and U≡N core molecules as terminal uranium nitrides with full triple bonds.