Some new phosphorus(III) derivatives Ar₂PX (X = Br, Cl, F or H), ArPX₂ (X = Br or Cl), Ar₃P and Ar^tBuPCl, with the 2,5-bis(trifluoromethyl)phenyl (Ar) substituent on phosphorus, have been prepared, and characterised by ³¹P and ¹⁹F NMR solution-state spectroscopy. The complexing ability of Ar₂PX, Ar₃P and Ar^tBuPCl towards the dimeric platinum(II) complexes [PtY(μ-Y)(PEt₃)]₂ (Y = Cl or Br, the latter for X = Br only) has also been investigated. Single-crystal X-ray diffraction studies at low temperature have been carried out for Ar₃P, Ar₂PCl and the hydrolysis or oxidation products Ar₂P(H)OH and Ar₂P(O)OH. The structures of Ar₃P and Ar₂PCl are particularly interesting as in each compound the geometry around P is approximately octahedral. In Ar₃P there are three short contacts to fluorine as well as the three bonded C atoms for both of the independent molecules in the unit cell. For Ar₂PCl there are two short P–F contacts, and the octahedron is completed by a weak P–P interaction to a neighbouring molecule. In both instances the lone pair on the P(III) centre appears to be stereochemically inactive, and does not play a significant role in the structure.