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

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Fluorine Chemistry

Background:

• Organometallic chemistry with ligands of higher than five hapticity (e.g., η7-cycloheptatrienyl) is less explored than η5-cyclopentadienyl systems due to stability concerns.
• Existing perfluoroalkyl metal chemistry lacks reported η7-cycloheptatrienyl derivatives, unlike their alkylated counterparts.

Purpose of the Study:

• To synthesize and characterize the first cycloheptatrienyl molybdenum complexes featuring a trifluoromethyl moiety.
• To investigate the stability of these novel organometallic compounds.

Main Methods:

• Synthesis of trifluoromethyl-containing cycloheptatrienyl molybdenum complexes using Morrison's trifluoromethylating reagent.
• Characterization of the synthesized complexes: (η7-C7H7)Mo(CO)2CF3 (I) and (η7-C7H7)Mo(CO)(PMe3)CF3 (II).

Main Results:

• Successful synthesis and characterization of two new complexes: (η7-C7H7)Mo(CO)2CF3 and (η7-C7H7)Mo(CO)(PMe3)CF3.
• The synthesized complexes were found to possess low thermal instability.

Conclusions:

• The study successfully introduced the first trifluoromethyl-substituted cycloheptatrienyl molybdenum complexes.
• The low thermal stability of these complexes underscores the challenges associated with higher hapticity organometallic compounds in perfluoroalkyl metal chemistry.