2460
Inorg. Chem. 1990, 29, 2460-2466
concentrations, the photoreaction does not appear to occur, presumably because the back-reaction proceeds faster than the photolysis. Likewise, at sufficiently low concentrations the back-reaction of the photolyzed complex is not observed. Titration of the resultant yellow solution (at concentrations where the back-reaction is negligible) with ferrous sulfate yielded Prussian blue, which was then filtered out of the solution. The remaining filtrate showed a UV-vis absorption at the same wavelength as that of Pt(NH3)4(N03)2. These results demonstrate that the starting products are regenerated upon photolysis by irradiation into the IT band. Others have reported charge-transfer photoreactions for binuclear cyanide-bridged specie^.^ Vogler, for example, demonstrated that the photolysis of [(NC)5C011'-NCO S I I ( C N ) ~ leads ] ~ via photoinduced electron transfer to the reactants from which it was formed by a thermal reaction, namely [Coil(CN),]-'- and (OS~~~(CN),]~-." However, to the best of our knowledge, the observation of a photoinduced two-electron charge-transfer based on a MMCT transition, as observed in the current case, has not previously been observed. Conclusions Since all of the photochemical experiments described were carried out at low light intensity (Le.
