Syntheses and Characterization of the First Cycloheptatrienyl Transition-Metal Complexes with a M-CF₃ Bond

The organometallic chemistry of metal complexes with organocyclic ligands of higher than five hapticity is much more lacking than the chemistry of metal complexes with η⁵-cyclopentadienyl ligands, which has been explored in considerable depth, resulting in novel advances. The main reason for this is stability. In particular, reports indicate that (η⁷-C₇H₇)ML_n complexes are considerably less stable than analogous (η⁵-C₅H₅)ML_n. In perfluoroalkyl metal chemistry, there is currently no reported (η⁷-C₇H₇)ML_n derivative, whereas a number of alkylated ones are known and important conclusions have been drawn about their stability. Responding to this void, and using Morrison's trifluoromethylating reagent, the present study reports the synthesis and characterization of the first cycloheptatrienyl molybdenum complexes bearing the trifluoromethyl moiety; (η⁷-C₇H₇)Mo(CO)₂CF₃ (I), and (η⁷-C₇H₇)Mo(CO)(PMe₃)CF₃ (II) and discusses their low thermal instability.