EPR EVIDENCE FOR THE FORMATION OF THE 6-COORDINATE PENTAFLUORONITRIDOTECHNETATE(VI) ANION IN SOLUTION

The reaction of AsPh(4)[TcNX(4)] (X = Cl or Br) with 'naked' F- in MeC N solution has been shown by e.p.r. spectroscopy to result in the faci le substitution of the halo ligands by fluoride. Addition of six equiv alents of NBu(4)F . 3H(2)O has provided, for the first time, direct ev idence for the formation of the six-coordinate [TcNF5](2-) in solution . An e.p.r. study of ligand exchange of Cs-2[TcNCl5] (4 x 10(-2) - 5 x 10(-4) mol dm(-3)) in 28.6 mol dm(-3) aqueous HF has shown that the d istribution of the five [TcNF(n)Cl4(4-n)](-) (n = 0-4) species is conc entration dependent, with the formation of [TcNF4](-) being favoured b y dilution.