Reactions of laser-ablated Co and Ni atoms with nitrogen atoms and molecules. Infrared spectra and DFT calculations of metal nitride molecular species and complexes

Laser-ablated Co and Ni atoms, co-deposited with pure nitrogen at 10 K, gave a strong new 795.3 cm(-1) band with cobalt and a 838.8, 836.1 cm(-1) isotopic doubler (2.5/1.0) with nickel, which exhibited 14/15 isotopic ratios appropriate for the diatomic CoN and NiN molecules. In solid argon, CoN absorbs at 826.5 cm(-1) and gives way on annealing to bands at 795.8 and 792.0 cm(-1), which are due to (NN)(x)CoN complexes. Density functional theory (DFT) calculations predict quintet and quarter ground states for CoN and NiN, respectively, and frequencies in reasonable agreement with the observed values. Evidence is also presented for the dimetal dinitrides, (CoN)(2) and (NiN)(2), with rhombus structures and metal-metal bonding across the ring. DFT-based calculations and revised assignments are presented for NI-NN stretching modes in the dinitrogen complexes.