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. 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.