Reactions of iron atoms with nitric oxide and carbon monoxide in excess argon: Infrared spectra and density functional calculations of iron carbonyl nitrosyl complexes

Laser-ablated iron atoms react with CO and NO during condensation in excess argon to produce a series of iron carbonyl nitrosyl complexes. The Fe(CO)( NO), Fe(CO)(2)(NO), Fe(CO)(NO)(2), and Fe(CO)(2)(NO)(2) complexes are forme d as reaction products during sample deposition and further annealing, whic h leads to dominance for the saturated Fe(CO)(2)(NO)(2) complex. The Fe(CO) (NO) complex isomerizes to Fe(CO)(eta (2)-NO) on visible photolysis and to the isocyanate species OFeNCO on ultraviolet irradiation. The observed abso rption bands were identified by isotopic substitution ((CO)-C-13-O-16, (NO) -N-15-O-16, (NO)-N-15-O-18. and mixtures) and reproduced by DFT calculation s of vibrational fundamentals. The FeCO subunit observed here in different nitrosyl environments appears to distort and stiffen with an increase in po sitive charge on iron, which may relate to thr deformability of the FeCO su bunit in heme proteins. The nature of bonding and reaction mechanism are di scussed.