Initial investigations into the catalytic HDF of pentafluoropyridine (1) by simple phosphines probed whether 1 and PhSiH3 could form 2,3,5,6-tetrafluoropyridine (2) in the presence of catalytic P( i Pr)3 (10 mol%) under similar reaction conditions to those used by Dobrovetsky and co-workers (o-C6H4F2 at 60 o C, Table , entry 1). After 18 hours we were pleased to find that 2 was formed, albeit in only modest, 26%, yield. The 19 F NMR spectra of the reaction mixture showed peaks at  = -92.9 and -141.5 ppm indicative of the ortho-and meta-fluorine environments of 2 respectively. Unreacted 1 could also clearly be seen (65%) and 9% of the product of reductive coupling of 1, perfluoro 4,4'-bipyridine (3) was also formed, identified through F NMR signals at  = -95.0 and -137.2 ppm. A control experiment under the same conditions showed that 1 and PhSiH3 did not form 2 in the absence of a phosphine (see SI for details). These results demonstrate for the first time that catalytic HDF is possible using only a simple trialkylphosphine as the catalyst. However, the reaction was significantly slower than that reported by Dobrovetsky and co-workers, who observed 95% yield of 2 in only 3 hours at 80 o C with a geometrically constrained P(III) catalyst. The simple nature of the phosphine and silane in our system allowed for straightforward reaction optimisation with a range of potential catalysts and hydride sources. Our focus here was not only on rate and selectivity, but also to make use of the simplest, most widely available and cheapest catalysts and supporting reagents in order to ensure that reactions are widely applicable.