Cationic Molybdenum Imido Alkylidene Complexes

Addition of 1 equiv of [HNMe2Ph]BAr4 (Ar ) 3,5-(CF3)2C6H3) to Mo(NAr)(CHCMe2Ph)(Pyrrolide)2 (Pyrrolide ) parent pyrrolide (Pyr) or 2,5-dimethylpyrrolide (Me2Pyr)) species in THF produced [Mo(NAr)(CHCMe2Ph)(Pyrrolide)(THF)x]BAr4 species (x ) 2 for Me2Pyr (1b) or 3 (1a) for Pyr; Ar ) 2,6-diisopropylphenyl). [Mo(NAr)(CHCMe2Ph)(Me2Pyr)(2,4-lutidine)]BAr4 (1c) was formed upon addition of 2,4-lutidine to [Mo(NAr)(CHCMe2Ph)(Me2Pyr)(THF)2]BAr4 (1b). Addition of 1 equiv of hexafluoro-tert-butanol to 1a produced {Mo(NAr)(CHCMe2Ph)[OC(CF3)2Me](THF)3}BAr4 (3a), while {Mo(NAr)(CHCMe2Ph)[OCMe(CF3)2](THF)2}BAr4 (3b) was obtained similarly through addition of hexafluoro-tert-butanol to 1b. Similar reactions produced unstable [Mo(NAr)(CHCMe2Ph)(O-2,6-iPr2C6H3)(THF)]BAr4 (3c) and [Mo(NAr)(CHCMe2Ph)(OAdamantyl)(THF)2]BAr4 (3d). Treatment of 1b with 2 equiv of 2,6-diisopropylphenol yielded [Mo(NAr)(CH2CMe2Ph)(O-2,6-i-Pr2C6H3)2]BAr4 (4). Compound 3a reacts with ethylene to yield {Mo(NAr)(CH2CH2)[OC(CF3)2Me](THF)3}BAr4 (6). The reaction between Mo(NAr)(CHCMe2Ph)(OTf)2(dme) and 2 equiv of Li(MesPyr) (MesPyr ) 2-mesitylpyrrolide) gave Mo(NAr)(CHCMe2Ph)(MesPyr)2 (2), but no cationic species could be prepared that contain 2-mesitylpyrrolide. Compounds 1a, 1c, 2, 3a, 4, and 6 were characterized crystallographically.