Selective C–H bond activation of 1,2,4,5-tetrafluorobenzene by Co(PMe3)4

Co(I) complex (p-C6F4H)Co(PMe3)3 (1) was obtained by the selective activation of the C–H bond of 1,2,4,5-tetrafluorobenzene (C6F4H2) with cobalt(0) complex, Co(PMe3)4. At the same time, 1,2,4-trifluorobenzene was observed as the hydrodefluorination product. The reaction of C6F4H2 with Co(PMe3)4 under 1 bar of CO at room temperature afforded dicarbonyl cobalt(I) complex (p-C6F4H)Co(CO)2(PMe3)2 (2). Treatment of the mixtures of C6F4H2/Co(PMe3)4 with hexachlorobenzene resulted in stable cobalt(II) chloride (p-C6F4H)CoCl(PMe3)3 (3) via C–H bond cleavage with the hydrodechlorination products pentachlorobenzene (C6Cl5H) and 1,2,4,5-tetrachlorobenzene C6Cl4H2. The structures of complexes 2 and 3 were determined by X-ray single crystal diffraction.