Mixed trihalophosphine complexes of nickel(0) and platinum(<small>II</small>)

[First page in lieu of Abstract] Trihalophosphine complexes of the transition metals are well established although little is known on relative bond strengths of e.g. trifluorophosphine complexes as compared with trichlorophosphine complexes. When [Ni(PF₃)₄] was originally prepared (1) it was noted that a yellow colour was developed with phosphorus tribromide and it was considered that a mixed species [Ni(PF₃)₃PBr₃] might be formed but there was no direct evidence for this. The difficulty of purification of [Ni(PF₃)₄] has also been noted (2). The thermal stability of the nickel complexes (1), and presumably of other metal derivatives, is [Ni(PF₃)₄] &gt; [Ni(PCl₃)₄] &gt; [Ni(PBr₃)₄] but this order has no direct relation to the M–P bond strengths.<br> Addition of PF₃ to [Ni(PCl₃)₄]; of PCl₃ to [Ni(PF₃)₄]; or mixing together [Ni(PF₃)₄] and [Ni(PCl₃)₄] all at 308K and either neat or in C₆D₆ gives yellow solutions together with some black solid. The ³¹P and ¹⁹F n.m.r. spectra of the solutions (Table 1) show identical species identified as the various mixed species [Ni(PF₃)_4−x(PCl₃)_x] (x = 0 to 4). The reactions occur over 1 to 3 days at 308K except for that between [Ni(PF₃)₄] and [Ni(PCl₃)₄] which is complete within the time of mixing and placing the specimen within the n.m.r. spectrometer. Complexes of mixed halo-species were not observed and under the conditions used there is no reaction between free PF₃ and free PCl₃.