Reactivity of a palladium fluoro complex towards silanes and Bu3SnCH = CH2: catalytic derivatisation of pentafluoropyridine based on carbon-fluorine bond activation reactions

摘要

The chloro and azido complexes trans-[PdCl(4-C5NF4)(PiPr(3))(2)] ( 3) and trans-[Pd(N-3)(4-C5NF4)(PiPr(3))(2)] ( 4) can be prepared by reaction of [PdF(4-C5NF4)(PiPr(3))(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(PiPr(3))(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)(PiPr(3))(2)] ( 2) with Bu3SnCH=CH2 in THF at 50 degrees C results in the formation of [Pd(PiPr(3))(2)] ( 1) and 4- vinyltetrafluoropyridine ( 7). Complex 2 is also active as a catalyst towards a Stille cross-coupling reaction of pentafluoropyridine with Bu3SnCH= CH2 to give 4-vinyltetrafluoropyridine ( 7) with a TON of 6. The molecular structure of the complex 3 has been determined by X-ray crystallography.