Reactions of Laser-Ablated Molybdenum and Tungsten Atoms with Nitric Oxide. Infrared Spectra of the MN, NMO, and M-η1-(NO)x (x = 1, 2, 3, 4) Molecules and (NO)2+ and (NO)2- Ions in Solid Argon

Laser-ablated Mo and W atoms react with NO to give primarily the nitride−oxide insertion products NMoO and NWO, but weak MoN and WN absorptions are also observed. The NMoO and NWO molecules are identified from isotopic substitution (nMo, 15N, 18O) and density functional theory (DFT) calculations. The M−N and M−O stretching frequencies of the 2A‘ state NMoO and NWO molecules are predicted by DFT (scale factors 0.936 ± 0.004 and 0.966 ± 0.005, respectively), but more importantly, the isotopic shifts (and normal modes) are well-described by DFT isotopic frequencies. The higher energy MoNO isomer is observed, but WNO and the M-η2-NO complexes are not found. The M-(η1-NO)x (x = 2, 3, 4) complexes are observed:  mixed isotopic splittings indicate that Mo(NO)4 is tetrahedral, like Cr(NO)4, but the spectra show that W(NO)4 is distorted to C2v symmetry. In addition, a weak 3643.5 cm-1 combination band and strong 1589.3 cm-1 fundamental for (NO)2+ and the strong fundamentals for cis- and trans-(NO)2- were observed.