Reactions of Laser-Ablated Molybdenum and Tungsten Atoms with Nitric Oxide. Infrared Spectra of the MN, NMO, and M-η-(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 ( n Mo, 15 N, 18 O) and density functional theory (DFT) calculations. The M−N and M−O stretching frequencies of the 2 A‘ 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-η 2 -NO complexes are not found. The M-(η 1 -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 C 2 v 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.