Infrared Spectroscopic and Theoretical Studies on the OMF₂ and OMF (M = Cr, Mo, W) Molecules in Solid Argon

Group 6 metal oxide fluoride molecules in the form of OMF₂ and OMF (M = Cr, Mo, W) were prepared via the reactions of laser-ablated metal atoms and OF₂ in excess argon. Product identifications were performed by using infrared spectroscopy, ¹⁸OF₂ samples, and electronic structure calculations. Reactions of group 6 metal atoms and OF₂ resulted in the formation of ternary OCrF₂, OMoF₂, and OWF₂ molecules with C_2v symmetry in which the tetravalent metal center is coordinated by one oxygen and two fluorine atoms. Both OCrF₂ and OMoF₂ are computed to possess triplet ground states, and a closed shell singlet is the ground state for OWF₂. Triatomic OCrF, OMoF, and OWF molecules were also observed during sample deposition. All three molecules were computed to have a bent geometry and quartet ground state. A bonding analysis showed that the OMF₂ molecules have highly ionic M-F bonds. ³OCrF₂ and ³OMoF₂ have an M-O double bond composed of a σ bond and a π bond. ¹OWF₂ has an M-O triple bond consisting of a σ bond, a π bond, and a highly delocalized O lone pair forming the other π bond. The M-O bonds in the OMF compounds have triple-bond character for all three metals.