PHOTOCHEMISTRY OF THE PTCL62- COMPLEX IN METHANOL SOLUTION

In the laser flash photolysis of PtCl62- in methanol, a non-linear dependence of the yields of the trivalent platinum intermediates PtCl63- and PtCl52- on laser pulse intensity is observed. The non-linearity is due to the absorption of photons by PtCl63- which is a primary product resulting from the electron transfer from a methanol molecule to excited PtCl62-. Photodissociation of PtCl63- yields PtCl52-. However, PtCl63- in the ground state also dissociates into PtCl52- and Cl-. This monomolecular process proceeds with an activation energy of 29.7 kJ mol-1 and a rate constant of 1.05 × 106 s-1 at 300 K. The parameters of the reverse reaction between Cl- and PtCl52- which yields PtCl63- have also been measured (activation energy, -9.6 kJ mol-1; rate constant at 300 K, 7.6 × 106 M-1 s-1). When free Cl- is present in methanol at a concentration of more than 0.1 - 0.2 M, electron transfer from Cl- to excited PtCl62- is also possible. The chlorine atom formed reacts with Cl- yielding the radical ion Cl2- which is detected by an intense absorption band with a maximum at 340 nm. © 1990.