Introduction of an electron-releasing substituent, in pentafluoroanisole, was not tolerated in this system with only traces of hydrodefluorinated products observed after 7 days at 60 o C alongside the majority of the starting material remaining unreacted. The use of bromopentafluorobenzene as a substrate also resulted in no conversion to the hydrodefluorinated product 9 after 20 minutes at 20 o C. However, in this case a small amount of pentafluorobenzene (3%) was formed and a new species was seen in the F NMR spectrum at  = -128.4, -142.9, -158.3 ppm (11%). This was associated with a signal in the P NMR spectrum at 36.6 ppm, which was the major phosphorus-containing product.