Molybdenum Imido Alkylidene Complexes that Contain a β-Diketiminate Ligand

The molybdenum β-diketiminate complexes Mo(NR)(CHCMe2R‘)(Ar-nacnac)(OTf) (R = 2,6-diisopropylphenyl, 2,6-dimethylphenyl, 1-adamantyl, 2,6-dichlorophenyl, or 2-tert-butylphenyl; Ar = 2,6-dichlorophenyl, 2,6-dimethylphenyl, 3,5-dimethylphenyl, or 2,6-difluorophenyl; R‘ = Me or Ph; Ar-nacnac = [ArNC(Me)]2CH; OTf = trifluoromethanesulfonate) have been prepared from Mo(NR)(CHCMe2R‘)(OTf)2(DME) by metathesis with the corresponding Li{Ar-nacnac} salt. Reaction of Mo(NR)(CHCMe2R‘)(Ar-nacnac)(OTf) with NaBArf4 (Arf = 3,5-(CF3)2C6H3) in the presence or absence of THF affords the cationic species {Mo(NR)(CHCMe2R‘)(Ar-nacnac)(THF)n}{BArf4} (n = 0 or 1) depending on the nature of Ar. The reactivity of the cationic β-diketiminate (nacnac) complexes toward olefins has been examined, as has the thermal decomposition modes of the neutral and cationic nacnac complexes. Results demonstrate that the cationic species have short catalyst lifetimes and that decomposition modes dominate the chemistry of several of the nacnac complexes.