Selective C–F and C–H Activation of Fluoroarenes by Fe(PMe₃)₄ and Catalytic Performance of Iron Hydride in Hydrosilylation of Carbonyl Compounds

The reactions of perfluorinated toluene (CF₃C₆F₅), pentafluoropyridine (C₅NF₅), and hexafluorobenzene (C₆F₆) with the iron(0) complex Fe­(PMe₃)₄ were investigated. The Fe­(I) complexes (4-CF₃C₆F₄)­Fe­(PMe₃)₄ (1), (4-C₅NF₄)­Fe­(PMe₃)₄ (2), and (C₆F₅)­Fe­(PMe₃)₄ (3) were obtained by selective activation of the C–F bonds. However, under similar reaction conditions, the reaction of Fe­(PMe₃)₄ with perfluoronaphthalene (C₁₀F₈) afforded a π-coordinated Fe(0) complex, (η⁴-1,2,3,4-C₁₀F₈)­Fe­(PMe₃)₃ (4), and the expected C–F bond activation reaction was not observed. The expected iron hydride (C₆F₅)­FeH­(PMe₃)₄ (6) could be obtained in a yield of 80% by the reaction of bromopentafluorobenzene with Fe­(PMe₃)₄ and subsequent reduction with NaBH₄. The molecular structures of complexes 2, 4, and 6 were determined by single-crystal X-ray diffraction. Complexes 1–4 and 6 could be used as catalysts for the hydrosilylation of carbonyl compounds. Among them, complex 6 is the best catalyst. The selective reduction of carbonyl groups of α,β-unsaturated aldehydes and ketones was also realized with 6 as catalyst.