The trifluorophosphoranes TrtRPF 3 (R = tert.-Bu (1), Ph (2), NEt 2 (3)) were obtained by the oxidative addition of TrtF (Trt = triphenylmethyl) to the difluorophosphines RPF 2 . At room temperature only 1 exhibited dynamic behaviour in solution, but at ±5 °C the pseudorotation was slow enough to permit the differentiation of 1 J(PF ax ) and 1 J(PF eq ) by 31 P NMR spectroscopy. X-ray structure analyses of 1, 2, and 3 confirm the expected trigonal bipyramidal geometry at phosphorus, with axial fluorine substituents. The trifluorophosphoranes 1±3 are of such stability towards water that hydrolysis was effected only under vigorous, basic conditions. The action of HCl or HBr on Trt(NEt 2 )PF 3 (3) led, in a complex reaction, to the formation of TrtPF 4 (5), besides 3 and PF 3 . As first observed for 1 by NMR spectroscopy at elevated temperature, in the case of 1 and 2 an equilibrium exists between TrtRPF 3 and TrtF/RPF 2 . Accordingly, it was possible to trap TrtF or RPF 2 by addition of I 2 , PCl 3 , AlCl 3 , and tetrachloro-o-benzoquinone (TOB) to solutions of 1 or 2. 3 was unreactive towards I 2 and PCl 3 , whereas treatment with AlCl 3 caused formation of (Et 2 N)PCl 2 by cleavage of the P±C bond, and halogen exchange. If a mixture of toluene and ether was used, LiAlH 4 reduced 1 and 2 to the corresponding secondary phosphines 8 and 9, while if only diethyl ether was employed under the same conditions, P±C bond rupture occurred in 2, and a mixture of PhPH 2 and TrtH was obtained.