The reaction of coordinatively unsaturated W(CO)(5) with NO is investigated using density functional theory. B3LYP-based calculations with ECPs (LANL2DZ) on W and 6-311+G(2d) all-electron basis sets on C, N, and 0 are used to characterize transients observed in the vibrational absorption spectra of CO and NO ligands observed by a time-resolved infrared absorption spectroscopy after the 355nm pulse laser photolysis Of W(CO)(6)/NO/Ar mixture [Y. Ishikawa and S. Arai, Chem. Phys. Lett. 253 (1996) 230]. The calculations suggested that, in the gas phase reaction of NO with W(CO)(5), simple coordination to form W(CO)(5)(NO) does not occur but, instead, sequential concerted displacement of CO takes place to form W(CO)(3)(NO)(2). (c) 2007 Elsevier B.V. All rights reserved.