The fact that an alloy had been prepared as a result of the co-reduction was finally proved by recording a Mossbauer spectrum (source: 57Co/Pt, 27 T ) [ l o l of the sample before heat treatment. The spectrum shows the characteristic six resonance lines for metallic iron. The total splitting (i.e., the distance between the outer lines) is 36 T, a value which has been found for comparable alloys formed by melting but which is 3 T larger than for pure iron.
Therefore the co-reduction of metal salts in organic solvents with hydroorganoborates provides a method of preparing single-phase, almost amorphous alloys of two or more components (Table ).
The redox potential of sodium hydrotriethylborate in T H F (supporting electrolyte: NBu,PF,) was determined electrochemically to be -0.77 V, corresponding to -0.62 V in H,O.["l Thus, the reaction between the metal salt and the hydride proceeds either as a reduction or as a metathesis depending on the particular metal involved. The findings described above can be rationalized on the basis of the HSAB concept."'] The metal ions M@ act as soft acids and compete with the moderately hard acid BR3[13] for the soft basic hydride ion to form 1. If Me is a softer acid than BR,, the hydride is transferred to M@, the resulting MH then decomposes spontaneously to metal and hydrogen [Eq. (d)].