Fluoro Nitrenoid Complexes FN=MF (M=Co, Rh, Ir): Electronic Structure Dichotomy and Formation of Nitrido Fluorides N≡MF.

The fluoronitrenoid metal complexes FNCoF and FNRhF as well as the first ternary Rh and Ir complexes NIrF and NRhF are described. They were obtained by the reaction of excited Group-9 metal atoms with NF and their IR spectra, isolated in solid rare gases (neon and argon), were recorded. Aided by the observed N isotope shifts and quantum-chemical predictions, all four stretching fundamentals of the novel complexes were safely assigned. The F-N stretching frequencies of the fluoronitrenoid complexes FNCoF (1056.8 cm ) and FNRhF (872.6 cm ) are very different and their N-M bonds vary greatly. In FNCoF , the FN ligand is singly bonded to Co and bears considerable iminyl/nitrene radical character, while the N-Rh bond in FNRhF is a strong double bond with comparatively strong σ- and π-bonds. The anticipated rearrangement of FNCoF to the nitrido Co complex is predicted to be endothermic and was not observed.