The photochemistry of M(mnt)22-(M = Ni, Pt) in CHCl3-CH3CN solvent mixtures was investigated upon excitation in the near-UV region of the spectrum. In both complexes, the quantum yield increasing concentration of CHCl3 UP to a limiting value of 0.014 and 0.024 for Ni(mnt)22- and Pt(mnt)22-, respectively, under 365-nm excitation. Similar behavior was observed upon 313-nm photolysis, but in this case, the limiting quantum yields were 0.25 and 0.14 for Ni(mnt)22- and Pt(mnt)22-, respectivelY. Normalization of the quantum yields with respect to the limiting quantum yield for each wavelength yields identical solvent dependence curves for both complexes indicating that the solvent dependence is independent of the wavelength dependence. Picosecond laser flash photolysis was used to probe the fundamental processes occurring in the photooxidation Of M(Mnt)22- (M = Ni, Pt). The picosecond spectra are identical in both halogenated and nonhalogenated solvents. No evidence for primary radicals which could limit yields by geminate recombination is found. It is proposed that the main factor which controls the reaction must be the electronic factor of mixing of the initially excited state with a CTTS state.