The reaction of PMe3 or PPh3 with PF s in anhydrous CH2Cl2 or hexane forms the white, moisture-sensitive complexes [PF5(PR3)] (R = Me, Ph). Similar reactions involving the diphosphines o-C6H4(PR2)(2) afford the complexes [PF4{o-C6H4(PR2)(2)}][PF6]. The X-ray structures of [PF6(PR3)] and [PF4{o-C6H4(PR2)(2)}][PF6] show pseudo-octahedral fluorophosphorus centers. Multinuclear NMR spectra (H-1, F-19{H-1}, P-31{H-1}) show that in solution in CH2Cl2/CD2Cl2 the structures determined crystallographically are the only species present for [PF5(PMe3)] and[PF4{o-C6H4(PR2)(2)}][PF6] but that [PF6(PPh3)] and [PF4{o-C6H4(PR2)(2)}][PF6] exhibit reversible dissociation of the phosphine at ambient temperatures, although exchange slows at low temperatures. The complex F-19{H-1} and P-31{H-1} NMR spectra have been analyzed, including those of the cation [PF4{o-C6H4(PMe2)(2)}(+), which is a second-order AA'XX'B2M spin system. The unstable [PF5(AsMe3)], which decomposes in a few hours at ambient temperatures, has also been isolated and spectroscopically characterized; neither AsPh3 nor SbEt3 forms similar complexes. The electronic structures of the PF5 complexes have been explored by DFT calculations. The DFT optimized geometries for [PF5(PMe3)], [PF5(PPh3)], and [PF4{o-C6H4(PMe2)(2)}(+) are in good agreement with their respective crystal structure geometries. DFT calculations on the PF5-L complexes reveal the P-L bond strength falls with L in the order PMe3 > PPh3 > AsMe3, consistent with the experimentally observed stabilities, and in the PF5-L complexes, electron transfer from L to PF5 on forming these complexes also follows the order PMe3 > PPh3 approximate to AsMe3.