Reactivity of a palladiumfluoro complex towards silanes and Bu3SnCHCH2: catalytic derivatisation of pentafluoropyridine based on carbon–fluorine bond activation reactions

Abstract

The chloro and azido complexes trans-[PdCl(4-C₅NF₄)(PiPr₃)₂] (3) and trans-[Pd(N₃)(4-C₅NF₄)(PiPr₃)₂] (4) can be prepared by reaction of [PdF(4-C₅NF₄)(PiPr₃)₂] (2) with Et₃SiCl or MeSiN₃, respectively. In contrast, reactions of 2 with Ph₃SiH or Me₂FSiSiFMe₂ give the products of reductive elimination 2,3,5,6-tetrafluoropyridine (5) or 4-(fluorodimethylsilyl)tetrafluoropyridine (6) as well as [Pd(PiPr₃)₂] (1). In a catalytic experiment, pentafluoropyridine can be converted with Ph₃SiH into 5 in 62% yield, when 10% of 2 is employed as catalyst. Treatment of trans-[PdF(4-C₅NF₄)(PiPr₃)₂] (2) with Bu₃SnCHCH₂ in THF at 50 °C results in the formation of [Pd(PiPr₃)₂] (1) and 4-vinyltetrafluoropyridine (7). Complex 2 is also active as a catalyst towards a Stille cross-coupling reaction of pentafluoropyridine with Bu₃SnCHCH₂ to give 4-vinyltetrafluoropyridine (7) with a TON of 6. The molecular structure of the complex 3 has been determined by X-ray crystallography.