Solvent influence on trifluoromethylation reactions with Cd(CF3)2: one-pot synthesis of trifluoromethyl iron complexes

Abstract

Bis(trifluoromethyl)cadmium complexes Cd(CF₃)₂·L (L = 2CH₃CN or CH₃OCH₂CH₂OCH₃) react as perfluoroalkyl Grignard reagents with carbonyl-iron halides in a one-pot reaction to yield Fe–CF₃compounds easily. A strong solvent influence is observed. The dependence of the direction of the reactions, either as a trifluoromethylation or a fluorination, is discussed. In the presence of CH₃CN a ligand-exchange reaction is observed, yielding trifluoromethyl iron acetonitrile complexes, while carbonyl complexes are obtained in ethers. The compound [Fe(CO)₄(CF₃)₂] has been prepared in 65% yield, and its ¹⁹F n.m.r., i.r., Raman, mass, and Mössbauer spectra recorded. The advantage of observing the ¹³C satellites in the ¹⁹F n.m.r. spectra for the analysis of trifluoromethyl metal compounds is established. If the appropriate reaction conditions are used, Cd(CF₃)₂ complexes react as fluorination reagents and CF₂ sources. Thus, on reaction of the trifluoromethyl cadmium reagents with tetracarbonyliron halides in CH₃CN, diamagnetic fluoroiron acetonitrile complexes are formed.