Redox chemistry of [Fe-2(CN)(10)](4-). Part 5. Reaction with thiourea

The reaction of the dimeric iron(III) complex [Fe-2(CN)(10)](4-) with a lar ge excess of thiourea, tu, takes place in a series of stages, the first two of which have been examined in detail. The first stage is a one equivalent outer sphere electron transfer to form [Fe-2(CN)(10)](5-) and the radical cation tu(+.) which dimerises to form the disulfide tu(2)(2+). There is kin etic evidence for the formation of a significant proportion of a precursor complex [Fe-2(CN)(10)](4-). tu at high concentrations of tu. The second sta ge involves cleavage of the mixed valence dimer to yield [Fe(CN)(5)tu](2-) and [Fe(CN)(5)H2O](3-). On standing, substitution of H2O by tu and oxidatio n by air occurs slowly, and finally all of the original iron is observed as [Fe(CN)(5)tu](2-).